USRE43843E1 - High bandwidth broadcast system having localized multicast access to broadcast content - Google Patents

Abstract

A method and arrangement is provided for the multicasting of streaming digital content to a plurality of Internet users. Streaming digital audio, video or other digital data content that is to be multicast to Internet users is formatted into IP protocol at a head-end content source transmission site. The streaming IP digital data is transmitted from the head-end transmission site to at least one distant/remote routing station of an Internet service provider (i.e., a provider-edge router or Internet point of presence) via a bandwidth portion of a digital communications data transport service or transmission medium that is substantially unaffected by conventional Internet communications traffic. The Internet service provider (ISP) maintains at least one access router for providing Internet access via its Internet domain for its customers accessing the Internet via conventional two-way IP connection. The streaming IP digital data received from the content source transmission site by the ISP routing station may then be multicast via the IPS's existing infrastructure to one or more of its Internet access customer.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of application Ser. No. 09/805,686, filed Apr. 19, 2000, now U.S. Pat. No. 6,411,616, which is a continuation of application Ser. No. 08/969,164, filed Nov. 12, 1997, now U.S. Pat. No. 6,101,180. In addition to being related to parent application Ser. No. 09/805,686, this continuation case is also related to the following continuation application (which also claims the benefit of priority from the Ser. No. 08/969,164 common parent application): Ser. No. 09/772,958, filed Jan. 31, 2001, entitled “High Bandwidth Broadcast System Having Localized Multicast Access to Broadcast Content” The present application also claims priority from related provisional applications: U.S. Ser. No. 60/029,427, filed Nov. 12, 1996; U.S. Ser. No. 60/039,672, filed Feb. 28, 1997; and U.S. Ser. No. 60/057,857, filed Sep. 2, 1997; all of the provisional applications are now abandoned.

BACKGROUND OF THE INVENTION

During the 1970's and 1980's, the defense industry encouraged and developed an interconnecting network of computers as a backup for transmitting data and messages in the event that established traditional methods of communication fails. University mainframe computers were networked in the original configurations, with many other sources being added as computers became cheaper and more prevalent. With a loose interconnection of computers hardwired or telephonically connected across the country, the defense experts reasoned that many alternative paths for message transmission would exist at any given time. In the event that one message path was lost, an alternative message path could be established and utilized in its place. Hence, it was the organized and non-centralized qualities of this communications system which made it appealing to the military as a backup communication medium. If any one computer or set of computers was attacked or disconnected, many other alternative paths could eventually be found and established.

This interconnection of computers has since been developed by universities and businesses into a worldwide network that is presently known as the Internet. The Internet, as configured today, is a publicly accessible digital data transmission network which is primarily composed of terrestrial communications facilities. Access to this worldwide network is relatively low cost, and hence, it has become increasingly popular for such tasks as electronic mailing and weather page browsing. Both such functions are badge or file transfer oriented. Electronic mail, for instance, allows a user to compose a letter and transmit it over the Internet to an electronic destination. For Internet transfers, it s relatively unimportant how long each file transfer takes as long as it is reasonable. The Internet messages are routed, not through a fixed path, but rather through various interconnected computers until they have reached their destination. During heavy message load periods, messages will be held at various internal network computers until the pathways cleared for new transmissions. Accordingly, Internet transmissions are effective, but cannot be relied upon for time sensitive applications.

Web pages are collections of data including text, audio, video, and interlaced computer programs. Each web page has a specific electronic site destination which is accessed through a device known as a web server, and can be accessed by anyone through via Internet. Web page browsing allows a person to inspect the contents of a web page on a remote server to glean various information contained therein, including for instance product data, company backgrounds, and other such information which can be digitized. The remote server data is access by a local browser, and the information is displayed as text, graphics, audio, and video.

The web browsing process, therefore, is a two-way data communication between the browsing user, who has a specific electronic address or destination, and the web page, which also has a specific electronic destination. In this mode of operation, as opposed to electronic mail functions, responsiveness of the network is paramount since the user expects a quick response to each digital request. As such, each browsing user establishes a two-way data communication, which ties up an entire segment of bandwidth on the Internet system.

Recent developments on the Internet include telephone, video phone, conferencing and broadcasting applications. Each of these technologies places a similar real-time demand on the Internet. Real-time Internet communication involves a constant two-way throughput of data between the users and the data must be received by each user nearly immediately after its transmission by the other user. However, the original design of the Internet to did not anticipate such real-time data transmission requirements. As such, these new applications have serious technical hurdles to overcome in order to become viable.

Products which place real-time demands on the Internet will be aided by the introduction of an updated hardware interconnection configurations or backbone,” which provides wider bandwidth transmission capabilities. For instance, the MCI backbone was recently upgraded to 622 megabytes per second. Regardless of such increased bandwidth, the interconnection configuration is comprised of various routers which may still not be fast enough and can therefore significantly degrade the overall end-to-end performance of the traffic on the Internet. Moreover, even with a bandwidth capability of 622 megabytes per second, the Internet backbone can maximally carry only the following amounts of data: 414-1.5 mbs data streams; 4,859-128 kbs data streams; 21597-28.8 kbs data streams; or combinations thereof. While this has anticipated as being sufficient by various Internet providers, it will quickly prove to be inadequate for near-future applications.

Internal networks, or Intranet sites, might also be used for data transfer and utilize the same technology as the Internet. Intranets, however, are privately owned and operated and are not accessible by the general public. Message and data traffic in such private networks is generally much lower than more crowded public networks. Intranets are typically much more expensive for connect time, and therefore any related increase in throughput comes at a significantly higher price to the user.

To maximize accessibility of certain data, broadcasts of radio shows, sporting events, and the like are currently provided via Internet connections whereby the broadcast is accessible through a specific web page connection. However, as detailed above, each web page connection requires a high throughput two-way connection through the standard Internet architecture. A given Internet backbone will be quickly overburdened with users if the entire set of potential broadcasters across world began to provide broadcast services via such web page connections. Such broadcast methods through the Internet thereby prove to be ineffective given the two-way data throughput needed to access web pages and real-time data.

Furthermore, broadcasts are typically funded and driven by advertising concerns. However, a broadcast provided through a centralized location, such as a web page for a real-time Internet connection, will be limited by practical concerns to offering only nationally advertised products, such as Coke or Pepsi. Since people might be connected to this web page from around the world, local merchants would have little incentive to pay to advertise to distant customers outside of their marketing area. Local merchants, on the other hand, would want to inject their local advertising into the data transmission or broadcasts in such a way not currently available on the Internet.

There is an enormous demand for the delivery of large amounts of content to a large number of listeners. The broadcast channels of today, such as radio and TV, can only deliver a small number of channels to a large number of listeners. Their delivery mechanism is well known to customers. The broadcaster transmits programs and the listener must tune in” at the proper time and channel to receive the desired show, “On Demand’ systems have been attempted by the cable industry. Such systems attempt to transport the program or show from a central repository (server) to the user (client) in response to his/her request. To initiate the request, the user selects from a list of candidate programs and requests that the system deliver the selected program.

The foregoing “on demand’ model of content delivery has placed two significant requirements on the delivery system. First, there typically is a direct connection between each content storage device (server) and each listener (client). The phone system is, an example of such a point-to-point interconnection system. Another example of such an interconnection system is the Internet, which is also largely based on the terrestrial telecommunications networks. Second, the server typically seeks to provide the capability of delivering all the programs to the requesting clients at the time that the client demands the programming.

The foregoing requirements can be achieved with limited success, particularly in conjunction with the Internet. The Internet is not suitable for many types of high bandwidth or on-demand systems. In today's Internet, Internet users most often share a terrestrial or perhaps even extra-terrestrial or wireless communications infrastructure; and as a result the total throughput is limited. In other words, the Internet is typically a party line shared by a large number of users and each subscriber must wait for the line to be free before he/she can send data. Since the signal from the server is generally a high bandwidth signal including multimedia content, any degradation of the throughput from the server to the clients results in an annoying disruption of the video and/or audio at the clients. Successful transmission of real-time streaming multimedia content, however, requires sufficient transmission bandwidth between the server and the client. Since standard IP transmission facilities are a party line, attempts have been made to impose a quality of service (QOS) into this dominantly party-line transmission structure. One such QOS feature is the bandwidth reservation protocol called “RSVP.” The RSVP protocol must be active in each network element along the path from the client to the server for it to be effective. Until RSVP is fully enabled, QOS cannot be guaranteed.

Once RSVP is fully deployed, then the mechanical process of reserving bandwidth will be possible to some degree. Nevertheless, even with RSVP, the problem remains that the Internet infrastructure provides limited transmission bandwidth. In this regard, consider the case where the sum of all bandwidth reservations exceeds available transmission bandwidth. To reduce the excessive use of bandwidth reservation, transmission providers anticipate transmission charges based on the amount of bandwidth reserved. This bandwidth charge is not in the spirit of today's free connectivity.

Another example of the limitations inherent in the finite throughput of the Internet is the generally limited audience size for a given transmission link. For example, if there is a 622 megabit/second (mbs) link from an Internet server in New York to a number of clients in Los Angeles and each client requires a separate 28.8 kilobit/sec (kbs) connection to the server, then this link can only support about 22,000 clients, a relatively small number of clients when compared to the cost of a server capable of supplying the 622 mbs data content. The costs further escalate and the client audience size capability further diminishes as each client connects to the server using higher bandwidth modems or the like. Still further, the same large demand is placed on the server if each of the 22,000 clients requests the same program but at different times or if each of the clients request a different program at the same, or nearly the same time. The large bandwidth requirements (622 mbs) to supply a relatively small number of clients (22,000) coupled with the stringent requirements placed on the server to supply the content to each client has created problems that “on-demand” systems have yet to economically overcome.

One prior art development in the LAN/WAN technology is called “multicasting.” Multicasting in LAN/WAN parlance means that only one copy of a signal is used until the last possible moment. For example, if a server in New York wants to deliver the same data to someone in Kansas City, Dallas, San Francisco, and Los Angeles, then only one signal needs to be sent to Kansas City. There it would be replicated and sent separately to San Francisco, Los Angeles, and Dallas. Thus the transmission costs and bandwidth used by the transmission would be minimized and the server in New York would only have to send one copy of the signal to Kansas City. This scenario is illustrated inFIG. 1A.

Multicasting helps to somewhat mitigate the transmission costs but there are still a great number of cases where it provides little optimization. For example, if there is one person in each city in the US that wants to view the same program generated by the server in New York, then the server must send the signal to all those cities, effectively multiplying the amount of bandwidth used on the network. As such, the transmission is still expensive. Further, the multicast system model breaks down at high bandwidths and during periods of low data throughput within the Internet infrastructure, resulting in annoying degradation of the transmission content.

Another issue is distribution of information between autonomous systems. This is called peering.FIG. 1B shows three autonomous simple systems labeled AS0, AS1 and AS2. These autonomous systems are self contained networks consisting of host computers (clients and servers) interconnected by transmission facilities. Each autonomous system is connected to other autonomous systems by peering links. These are shown inFIG. 1B by the transmission facilities labeled PL01, PL02 and PL12.

Peering allows a host in one autonomous system to communicate with a host in a different autonomous system. This requires that the routers at the end of the peering links know how to route traffic from one system to the other. Special routing protocols, such as boundary gateway protocol, enable the interconnection of autonomous systems.

Assume that host H1 in AS0 wants to communicate with host H2 in AS1 and H3 in AS2. To do this, H1 communicates with PL01 to reach H2 and PL02 to reach H3. If host H1 wants to multicast a message to multiple hosts in each of the autonomous systems, then boundary routers involved must understand the multicast protocols.

Backbone providers that form each of autonomous systems are reluctant to enable multicast over their peering links because of the unknown load placed on boundary routers and billing issues related to this new traffic which originates outside of their autonomous systems.

The present inventors have recognized that a different approach must be taken to provide a large amount of content to a large number of listeners. In their prior art published European patent application, the present inventors proposed a system that abandons the “on-demand” model and point-to-point connection models. In their place, the present inventors combined, among other things, a particular, unique “broadcast” model with localized multicast connections that selectively allow a client to receive the high bandwidth content of the broadcast.

As the present inventors' prior published patent application explained, the broadcast model assumes that the server delivers specific content at specific times on a specific channel as is currently done in today's radio and television industry. “Near on demand” can be affected by playing the same content at staggered times on different transmission channels, preferably, dedicated satellite broadcast channels. Localized receivers receive the broadcast channels and convey the content over a network using a multicast protocol that allows any client on the network to selectively access the broadcast content from the single broadcast. This single broadcast provides, in effect, an overlay network that bypasses congestion and other problems in the existing Internet infrastructure.

As also explained in the prior published application:FIG. 1C shows how host H1 multicast directly to H2 and H3 via satellite or another dedicated link separate from the backbone of the Internet. This type of interconnection bypasses the peering links and the resulting congestion and billing issues. This type of prior art interconnection maintains, however, a party-line sharing of bandwidth in the dedicated link. It also is, in essence, generally part of a two-way connection adapted to provided TCP/IP information exchange in cooperation with, typically, a terrestrial back channel from the satellite reception entity to the entity providing the content for transmission through the satellite or other dedicated link.

The applicants' prior published European application was therefore based on the applicant's discovery of, among other things, the advantage of using a separate dedicated link and implements the resulting solution in a unique manner. Accordingly, the present applicants provided a data transmission system capable of sending multiple channels of broadcast or multicasting data or “content” to receiving computers without being delayed or impaired by the bandwidth and constraints of two-way Internet connections.

The applicants' have discovered, however, that one problem with the applicants system is that, although the near-on-demand delivery is very advantageous, by itself, it does not allow for the level of flexibility an Internet user may desire in playing or accessing content on demand and, for example, long after the near-on-demand delivery has terminated for any given content.

Another problem that the applicants have discovered is that the broadcast model itself is unduly limited in its ability to meet the demands, and satisfy the needs of, providers of localized or regionalized advertising and similar types of localized content. The satellite broadcast model, for example, typically delivers the same content to all users nationally. This creates a significant problem for distribution of localized content, such as locally tailored advertising, through such a non-localized broadcast system. The providers of such locally tailored advertising frequently do not purchase advertising in such non-localized broadcasts, and the potential market demand for advertising through such mediums is correspondingly limited.

Similarly, those who seek to provide locally-tailored advertising have had to seek other avenues (such as dealing individually with localized broadcasters in each localized market) in order to advertise. This effort is time consuming and expensive.

Also, even when pursuing locally-tailored advertising, advertisers are often forced by the available traditional media to purchase advertising in unnecessarily large regions or for delivery to recipients who are not as targeted as might be desired by the advertiser. The applicants' embodiment disclosed in the applicants' prior art patent application did not solve this type of problem in and of itself.

SUMMARY OF THE INVENTION

The applicants have developed methods and apparatus for multicasting or broadcasting digital data to users accessing an Internet connection. The methods and apparatus preferably include placing digital data that is to be multicast in IP protocol to generate IP digital data. The IP digital data preferably is transmitted from a transmission site to a remote Internet point of presence through a dedicated transmission channel substantially separate from the Internet backbone. The dedicated transmission channel may be, for example, a satellite channel. At the remote Internet point of presence, local commercials preferably can be inserted into the IP digital data and/or the signal can be delayed for later playback. The IP digital data is then preferably multicast for delivery to a receiving Internet users apparatus connected to but distal from the remote Internet point of presence.

As will be readily recognized, the foregoing method and apparatus eliminate, or reduce the severity of, problems discussed above in connection with existing multicast or broadcasting systems. Further, since the principal equipment used to implement the method is disposed at the point of the Internet Service Provider, the normal psychological reluctance of an Internet user to purchase extraneous multicast equipment is avoided. Other significant advantages of the applicants' disclosed apparatus and method will become apparent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are drawings used to illustrate problems in inter-city, communications over, for example, the Internet using conventional systems.

FIG. 1C illustrates an alternative delivery system to the system ofFIG. 1B.

FIG. 1D illustrates a conventional network architecture.

FIG. 2 illustrates a hybrid broadcast I multicast network constructed in accordance with one embodiment of the present invention.

FIG. 3 illustrates one manner in which the Internet Protocol addresses may be mapped at an Internet Service Provider.

FIG. 4 is a block diagram of one embodiment of a file server station, such as one suitable for use in the conventional system ofFIG. 1.

FIG. 5 illustrates one embodiment of a routine station constructed in accordance with one embodiment of the present invention and its connection within a network domain.

FIGS. 6 and 7 illustrate use of a routing station constructed in accordance lip the invention and its connection at an Internet Service Provider.

FIG. 8a illustrates one embodiment of an uplink site suitable for use in the network ofFIG. 2.

FIG. 8b illustrates one embodiment of a downlink site suitable for use in the network ofFIG. 2.

FIGS. 9-11 illustrate various embodiments of downlink sites suitable for use in the network ofFIG. 2.

FIGS. 12 and 13 illustrate various manners in which various components of a downlink site may be modularized and interconnected.

FIG. 14 illustrates one embodiment of the multicast system at an ISP with distributed POPs that are interconnected with one another.

FIGS. 15 and 16 illustrate one embodiment of an IPMS.

FIG. 17 illustrates a packet protocol that may be used by the controller unit to communicate through the monitor and control interface software.

FIG. 18 illustrates one embodiment of a transponder unit.

FIG. 19 is a schematic block diagram of selected components of one embodiment of a transponder unit including a descrambler.

FIG. 20 illustrates one embodiment of a packet filter used in the transponder unit ofFIG. 18.

FIGS. 21-26 illustrate various configurations for networks using an IPMS constructed in accordance with the present invention.

FIGS. 27-29 illustrate a further manner of deploying the present system at an ISP.

FIG. 30 illustrates one example of a web page layout for use in selecting baud rate of a video transmission at a user of the present system.

DETAILED DESCRIPTION OF THE INVENTION

The current networking architecture of today is generally illustrated inFIG. 1D. As illustrated, the network, shown generally at50, comprises a group of host computers H1-H6 that are interconnected by transmission links P1-P13 and routers R1-R6 to form a LAN/WAN. An aggregated group of hosts is called a domain. Domains are grouped into autonomous systems that are, in-turn, interconnected together to form a network. When these networks span a large geographic area, they are called a wide area network or WAN. An example of this network architecture is the Internet and is illustrated inFIG. 1D.

At each interconnection node is a device called a router, designated here as R1-R6. The function of the router is to receive an input packet of information, examine its source and destination address, and determine the optimal output port for the message. These receive, route determinations, and transmit functions are central to all routers.

If host H1 wants to send a message to host H3, there are a variety of paths that the signal could take. For example, the signal could be transmitted along the transmission path formed by P1-P4-P8-P10. Other alternatives include the paths formed by P1-P2-P5-P7-P9-P10 or P1-P4-P6-P7-P9-P10. The function of the router is to determine the next path to take based on the source and destination address. The router might use factors such as data link speed or cost per bit to determine the best path for the message to follow.

As more host computers are brought on-line, more domains are created. Each time a domain is created, any router associated with the domain must announce to its peers that it is present and ready to accept traffic. Conversely if a domain is deleted, the system must respond by removing the paths and rerouting all messages around the removed domain. In any large network there will be a constant addition and removal of domains. The success of the network architecture to respond to these changes is at the core of the networking problem. To this end, each router communicates with its peers to announce to the network or networks it services. This implies that a bi-directional link should exist at each router. Terrestrial telephone circuits have traditionally supplied these links on the Internet.

FIG. 2 illustrates a hybrid broadcast/multicast constructed in accordance with one embodiment of the present invention. The system is illustrated in the context of a plurality of interconnected Internet domains A, B, and C. As noted above, a domain is an aggregate of one or more hosts. For example, domain A may be a corporate LAN while domain B may be a LAN at an educational institution or the like. In the illustrated embodiment, domain C is shown as an Internet Service Provider (ISP) that usually sells local access to the Internet through its domain. As such, domain C includes at least one access router R7 having one or more modems through which local but remotely located ISP customers (hosts)60 connect to the domain through POTS, T1 lines, or other terrestrial links. From domain C, theISP customers60 are connected to the Internet.

In the preferred embodiment, afile server station100 is used to store and transmit broadcast transmissions to asatellite55. As will be set forth in further detail below, thefile server station100 includes one or more file servers that can provide, for example, multimedia content in TCP/IP format. The multimedia data is then encapsulated in HDLC or similar frame format and modulated to RF for transmission over one or more uplink channels of thesatellite55. Thesatellite55 re-transmits the HDSL encapsulated frames on one or more downlink channels having different carrier frequencies than the uplink channels. The downlink transmissions are concurrently received by domains A, B, and C at local routine stations x1, x2, x3. At each routing station x1, x2, x3, the original TCP/IP data transmitted from thefile server station100 is extracted from the received HDLC frames. The extracted TCP/IP data is selectively supplied to hosts within the domain that have made a request to receive the data.

Thissatellite55 network in effect provides an overlay network that bypasses or at least somewhat avoids congestion and limitations in at least some of the existing Internet infrastructure, such as inFIG. 1. Moreover, thissatellite55 network provides dedicated, guaranteed bandwidth for the transmission of multimedia data through thesatellite55.

In the preferred embodiment, the transmissions from thefile server station100 preferably include one or more multimedia transmissions formatted in accordance with the IP multicast protocol. IP Multicast is an extension to the standard IP network-level protocol. RFC 1112, Host Extensions for IP Multicasting, authored by Steve Deering in 1989, describes IP Multicasting as: “the transmission of an IP datagram to a ‘host group’, a set of zero or more hosts identified by a single IP destination address. A multicast datagram is delivered to all members of its destination host group with the same ‘best-efforts’ reliability as regular unicast IP datagrams. The membership of a host group is dynamic; that is, hosts may join and leave groups at any time. There is no restriction on the location or number of members in a host group. A host may be a member of more than one group at a time.” In addition, at the application level, a single group address may have multiple data streams on different port numbers, on different sockets, in one or more applications.

IP Multicast uses Class D Internet Protocol addresses, those with 1110 as their high-order four bits, to specify groups ofIPMS units120. In Internet standard “dotted decimal” notation, host group addresses range from 224.0.0.0 to 239.255.255.255. Two types of group addresses are supported: permanent and temporary. Examples of permanent addresses, as assigned by the Internet Assigned Numbers Authority (LANA), are 224.0.0.1, the “all-hosts group” used to address allIP IPMS units120 on the directly connected network, and 224.0.0.2, which addresses all routers on a LAN. The range of addresses between 224.0.0.0 and 224.0.0.255 is reserved for routing protocols and other low-level topoloyy discovery or maintenance protocols. Other addresses and ranges have been reserved for applications such as 224.0.13.000 to 224.0.13.255 for Net News (a text based service). These reserved IP Multicast addresses are listed in RFC 1700, “Assigned Numbers.” Preferably, transmissions from thefile server100 containing related multimedia content are transmitted using a permanent address. Even more preferably, the same multimedia content is provided by thefile server system100 at multiple data rates using different permanent addresses.

For example, a multimedia file containing an automobile commercial may be concurrently transmitted for reception at a 28.8 KB data rate, a T1 data rate, an ADSL data rate, etc. The 28.8 KB transmission is transmitted using a first group of one or more permanent addresses. The T1 data rate transmission is transmitted using a second group of one or more permanent addresses, wherein the first group differs from the second group. In this manner, a client having a high speed Internet connection may chose to receive the more desirable high data rate transmissions while a client having a lower speed Internet connection is not precluded from viewing the content due to the availability of the lower speed data transmissions. Additionally, a corresponding web page may be concurrently transmitted along with the multicast data or along the backbone of the Internet.

If permanent multicast addresses are not available, the TCP/IP addresses used for the broadcast transmissions may use a block of addresses that are normally designated as administratively scoped addresses. Administratively scoped addresses are used for the transmission of commands and/or data within the confines of a domain for administrative processes and are not supplied outside of the scope of the domain. In other words, any broadcast transmissions received using these administratively scoped addresses desirably remains Within the bounds of the domain in which it is received. All addresses of the form 239.x.y.z are assumed to be administratively scoped. If administratively scoped addresses are used, provisions must be made to ensure that the domain does not use an administratively scoped address that is within the designated broadcast block for other system functions. This may be accomplished in one of at least two different manners. First, the domain can be reprogrammed to move the administratively scoped address used for the other system function to an administratively scoped address that does not lie within the broadcast block. Second, the routing station may perform an address translation for any administratively scoped addresses within the broadcast block that conflict with an administratively seeped address used for other purpose by the domain. This translation would place the originally conflicting address outside the conflict range but still maintain the address within the range of permissible administratively scoped addresses. As above, the same multimedia content is transmitted concurrently using different transmission data rates.

With respect to the use of administratively scoped addresses, assume that the system will utilize a block of addresses that contain 65,535 addresses (16 bits of address space). This block will utilize a predetermined, default address block. For the sake of this description, assume that the system default address space is defined as 239.117.0.0 to 239.117.255.255. This address space is defined by fixing the upper two bytes of the address space (in this case 239.117) while merely varying the lower two bytes of data to allocate or change the address of a channel of TCP/IP multimedia data. This addressing scheme, in and of itself, will provide the system with 64K possible channels but it may place restrictions on the ISP environment since they would be required to have a dedicated block of 64K address space, one in which none of the 64K addresses are being used by other applications. This may not always be feasible. In order avoid this kind of limitation, the system may only actually utilize the first 16K of the predefined address space. This will allow 16K channels for the entire system, which corresponds to a minimum aggregate data rate of 470 MHz (assuming every channel is running the minimum data rate of 28.8 kbps).

Even with the limited number of addresses, there are still two potential types of problems within the ISP environment. In the first type of problem, a limited number of the system broadcast addresses are already in use at the ISP or other domain type. In the second type of potential problem, a large block of the system broadcast address space is being used at the ISP or other domain type. In either case, the IPMS must be able to provide a solution for these two types of problems. These two cases are preferably addressed differently.

The most likely address conflict to be encountered in an ISP is the first one noted above, designated here as the “limited address” conflict. This type of conflict occurs when a single address or several isolated addresses within the broadcast address range are already allocated within the ISP or other domain type. The fact that only 16K addresses out of the 64K address block are used will provide a means for routine “around” these limited address conflicts.

As illustrated inFIG. 3, the 64K address space shown generally at80 will be divided into four 16K address blocks85. The following diagram shows how the address blocks are defined. The system default addresses are all located inblock 0 which begins ataddress 0 of the administratively scoped addresses.

The ISP or domain will setup a “routing table” within a routing station of the domain that indicates all of the administratively scoped addresses used within the ISP or domain. The routing station is programmed to re-route addresses with conflicts to the next available address block. For example, if the ISP has address 239.117.1.11 already assigned, the routing station routes this address to the next available block. The next available address block is found by adding 64 to the second byte of the IP address. For this service the next address would be 239.117.65.11. If this address is free, this is where the routing station re-routes the data associated with the conflicting address. Four alternate addresses may be assigned for rerouting a single channel having a conflicting address.

The address re-routing scheme should be implemented on both the routing station end and in any client Plug-In software used to receive the data. On the routing station side, once the ISP enters all address conflicts, the routing station performs address translation on all of the addresses that conflicts occur. All packets have their addresses re-mapped to the new location. If a single address can not be re-routed (all four address blocks are used for a given channel) then the receiver performs major address block re-routing as would occur in address block conflict management described below. On the client software side, the client opens sockets for all four address blocks (either sequentially or simultaneously). The address that provides valid broadcast data is accepted as the correct channel. The three other sockets are closed. If none of the addresses provide valid data, the client tries the alternate address block as defined below.

Alternative strategies for reconciling addressing conflicts may also be employed. As an example, an agent might be implemented with the IPMS which could be queried by the client for the appropriate address to use at a particular location. Such a query would include a “logical” channel number associated with the desired broadcast. The agent would then respond with the specific IP Address locally employed for that broadcast.

If a large number of addresses conflict with the default system address space, an alternate block of addresses will be used. The system defines the exact alternate address space (or spaces), but as an example, if 239.117.X.Y is the primary default broadcast block, an address space like 239.189.X.Y might be used as an alternate. In any event, the routing station will determine, based on the address conflicts entered by the ISP, if the entire broadcast address block must be re-routed. If it does, the routine station will modify each broadcast channel's address. As described above, if the client software can not find a valid broadcast stream within the standard address block, the alternate address space will be tried.

Routing multicast traffic is different than the routing of ordinary traffic on a network. A multicast address identifies a particular transmission session, rather than a specific physical destination. An individual host is able to join an ongoing multicast session by issuing a command that is communicated to a subnet router. This may take place by issuing a “join” command from, for example, an ISP customer to the ISP provider which, in turn, commands its subnet router to route the desired session content to the host to which the requesting ISP customer is connected. The host may then send the content using, for example, PPP protocol to the ISP customer.

Since the broadcast transmission is provided over a dedicated transmission medium (the satellite in the illustrated embodiment), problems normally associated with unknown traffic volumes over a limited bandwidth transmission medium are eliminated. Additionally, the number of point-to-point connections necessary to reach a large audience is reduced since the system uses localized connections within or to the domain to allow clients to join and receive the broadcast. In the illustrated embodiment, a virtually unlimited number of domains may receive the broadcast and supply the broadcast to their respective clients, additional domains being added with only the cost of the routing station at the domain involved. In most instances, ISPs or the like need only add a routing station, such as at x1 et seq., and may use their existing infrastructure for receiving broadcasts from the routing station for transmission to joined clients. This is due to the fact that most ISPs and the like are already multicast enabled using the IP multicast protocol.

FIG. 4 illustrates a block diagram of one embodiment of a file server station, such as the one illustrated at100 ofFIG. 1. The file server station, shown generally at100, comprises alocal area network102 with a collection ofserver PCs105 connected to arouter110 over thelocal area network102. Theserver PCs105 include server software that either reads pre-compressed files from the local disk drive and/or performs real time compression of analog real time data. Eachserver105 provides this data as output over the local area network.

TheLAN102 performs the function of multiplexing all the streaming data from theserver PCs105. TheLAN102 should have sufficient bandwidth to handle all the data from theserver PCs105. In present practice, 100 mbs LANs are common and, thus, it is quite feasible to use 100 mbs LANs to aggregate the data output to a 30 mbs transponder. A common type of LAN is or 100Base T, referring to 100 mbs over twisted pair wire.

The functionality required at110 is to gather the packets of data from theLAN102, wrap them in a transport protocol such as HDLC, and convert the HDLC packets to the proper voltage levels (such as R5422). The functionality can be provided by the composite signal provided from therouter110 usually comprises clock and data signals The composite signals are output from therouter110 for synchronous modulation by asatellite uplink modulator115 which synchronously modulates the data to the proper RF carrier frequencies and transmits the resulting signal through an antenna122 to thesatellite55.

One ormore server PCs105 of theLAN102 store the multimedia content that is to be broadcast to the domains. Alternatively, the one ormore PCs105 may receive pre-recorded or live analog video or audio source signals and provide the necessary analog-to-digital conversion, compression, and TCP/IP packet forming for output onto the LAN wanted. These packets are transported over theLAN102 in an asynchronous manner. Therouter110 then receives these asynchronous packets and encapsulates them with the transport protocol and transmits them in a synchronous manner to thesatellite55. The constant conversion from one form to another is provided to fit the transmission technologies of the transmission equipment. LANs are becoming ubiquitous and low cost since it leverages the high manufacturing volumes of the consumer/corporate PC market. Satellite transmission is extremely cost effective for broadcasting signals to multiple destinations and is inherently synchronous (data is transmitted at precise intervals). Accordingly, the foregoing system is currently the most straight forward and lowest cost method to architect a system a connecting computer LANs to a satellite transmission system.

Atypical satellite55 has two antennas, one for receiving the signal from the uplink and the second antenna for transmitting the signal to the downlink. An amplifier is disposed between the two antennas. This amplifier is responsible for boosting the level of the signal received from the file server station100 (uplink). The received signal is very weak because of the distance between the uplink and the satellite (typically about 23,000 miles). The received signal is amplified and sent to the second antenna. The signal from the second antenna travels back to downlinks which are again about 23,000 miles away. In the illustrated embodiment of the system, the downlinks are the routing stations.

The signal is transmitted by the uplink at one frequency and shifted to a different frequency in the satellite before amplification. Thus, the signal received by the satellite is different from the frequency of the signal transmitted. The transmitted information content is identical to the received information.

A typical satellite has approximately 20 to 30 RF amplifiers, each tuned to a different frequency. Each of these receive/transmit frequency subsystems is called a transponder. The bandwidth of each of the transponders is typically about 30 MHz but can vary satellite to satellite.

At thefile server station100, the composite signal from therouter110 is preferably QPSK modulated by the satellite uplink modulator. During the modulation process, extra bits are usually added to the original signal. These extra bits are used by a receiver at the downlink to correct any errors which might occur during the 46,000 mile transmission. The extra protection bits that are a added to the data stream are called Forward Error Correction bits (FEC).

The resulting modulation and error correction process typically allows about 1 megabit/second of data to occupy about 1 megahertz (MHz) of bandwidth on the transponder. Thus, on a 30 MHz bandwidth transponder, one can transmit about 30 mbs of data. The aggregate data rate of the signals generated by allserver PCs105, including the overhead of the underlying transmission protocols (IP and HDLC), must be less that the bandwidth of the satellite transponder.

FIG. 5 illustrates one embodiment of a routing station and its connection within a domain. Here, the routing station is called an IP Multicast Switch (IPMS), labeled as120 inFIG. 5. TheIPMS120 is comprised of ademodulator125 that receives the radio frequency signals from thesatellite55 over receiveantenna130 and converts them into the original TCP/IP digital data stream. These digital signals are then input to a device called a IP Multicast Filter (IPMF)140 that in-turn selectively provides the signals as output onto a LAN, shown generally at145, having sufficient capacity to handle all the received signals. TheIPMS120 is multicast enabled, meaning that data is only output from theIPMF140 onto theLAN145 if aclient160 requests a connection to receive a broadcast channel. As noted above; this multicast protocol may be one such as defined in RFC 1112.

As illustrated, theLAN145 can be connected to theInternet165 through arouter170. If the broadcast data output on theLAN145 uses administratively scoped addresses, therouter170 can prevent forwarding of the data to theInternet165. This is a desirable feature associated with the use of administratively scoped addresses, as the broadcast can be localized and blocked from congesting theInternet165. If other addresses are used, such as permanent IP multicast addresses, therouter170 is programmed to prevent data having an IP multicast address from being broadcast on theInternet165.

The software of theIPMS120 is capable of operating in an IP multicast network. In the embodiment described here, the control structure of the multicast software in theIPMS120 has four main threads: initialization, multicast packet handling, LAN packet handling, and multicast client monitoring. In the initialization thread, a table used to determine whether a client has joined a broadcast has its content set to an empty state. Initialization is performed before any of the other threads are executed.

The multicast packet handling thread is responsible for reading data from the satellite demodulator and deciding what is to be done with it. To this end, the thread reads each multicast packet received from thesatellite demodulator125. If the multicast group address specified in the received packet is not in a group table designating the groups received from thesatellite55 by thedemodulator125, the group address is added to the group table and set to “not joined.” If the multicast group address specified in the packet is specified in the join table as having been joined by a client, the packet is output through theIPMS120 to theLAN145 for receipt by a requestingclient160. If none of the foregoing tests are applicable, the packet is simply ignored.

The LAN packet handling thread is used to determine whether a join command has been received from aclient160 over theLAN145. To this end, theIPMS120 reads an IP packet from theLAN145. If the packet is a request from aclient160 to join the multicast session and it is in a group table (a table identifying groups which theIPMS120 is authorized to receive), the group address is added to the list of joined addresses in the join table. In all other circumstances, the packet may be ignored.

The multicast client monitoring thread is responsible for performing periodic checking to ensure that a multicast client who has joined a broadcast is still present on theLAN145. In accordance with RFC 1121, every predetermined number of seconds, or portions thereof, for each group address in the group table which has joined the multicast session a query is sent to that address and theIPMS120 waits for a response. If there is no response, theIPMS120 assumes that all joined clients have terminated and removes the group address from the joined list.

It will be recognized that other further software threads and variations on the foregoing threads may be used. However, in the simplest form of the illustrated embodiment, the four threads described above are all that is practically needed for effective IPMS operation where theIPMS120 is disposed at an outer edge of a domain network. This simplification provides a reduction in complexity in theIPMS120.

If there are one or more routers between theIPMS120 and themulticast client160, then theIPMS120 is programmed to understand the various multicast protocols such as DVMRP, MOSPF and RIM. These protocols are well known and can easily be implemented in theIPMS120.

In either configuration, theIPMS120 appears to the domain network as the source of the data, and the satellite link effectively places an identical server at each downlink location in the separate domains described in connection withFIG. 2.

It is generally preferable to have theIPMS120 as close as possible to the last point in the network before transmission to a client. This close proximity to the client minimizes the traffic burden on other system routers and the overall local LAN. The Internet Service Provider's (ISP) local Point of Presence (POP) is generally the optimum location for placement of theIPMS120 at an ISP. Such a configuration is illustrated inFIG. 6.

As shown inFIG. 6, the ISP, shown generally at200, is connected via anaccess router205 to theInternet165. If adistribution router210 is located some distance from theInternet access router205, then inter-POP communications are required through one or moreintermediate routers207. These inter-POP communications may take place via frame relay or SMDS (Switched Multimegabit Data Service) since these are relatively inexpensive communication methods. In thePOP215, theIPMS120 is connected to thebackbone LAN220. ThisLAN220 is connected to thedistribution router210 and provides the connectivity to the customer base. Typically, thedistribution router210 is connected to a Local Exchange Carrier (LEC)230 through telephone company interconnects such as T1, T3, and ATM lines and, thereafter, to remotely located home users/clients235.

The architecture ofFIG. 6 allowscustomers235 to place local (free) calls into thedistribution router210 that, in turn, allows thecustomers235 to access theInternet165 through some remote access point. If thePOP215 and the Internet access ataccess router205 are co-located, then theISP LAN240 and thePOP Backbone LAN220 are one in the same and there are no intermediate routers or intervening inter-POP communications.

FIG. 7 illustrates a system in which theIPMS120 is not disposed at thePOP215 location. This arrangement is functional, but requires a large amount of bandwidth over the inter-POP communication lines245. The configuration shown inFIG. 6 minimizes the bandwidth requirements of the router interconnections relative to the configuration shown inFIG. 7 since only the POP Backbone IAN should include both the traditional Internet traffic as well as the Multicast traffic.

As can be seen from examination ofFIGS. 6 and 7, the addition of multicast equipment to the ISP'sPOP215 is minimal. It is also possible and desirable to add atraffic server PC255 onto the LAN of theISP200 having the IPMF120 (also known as a multicast switch). Thistraffic server255 can be used for a varies of purposes, but in the embodiment shown here, it is used to store information received from thesatellite55 and theInternet165 for later playback. It also can be used to monitor the number and identification of a connected user as well as performing other functions. For example, when a user selects a video/audio multicast channel to view/hear, it sends a specific IGMP message over the LAN that is directed to theIPMS120. This message can also be monitored by all systems connected to the LAN. Specifically, thetraffic server255 may monitor the communication between therouter210 and any connected clients and may also monitor the number of connections to the multicast channels. The connection information gathered by thetraffic server255 is preferably relayed to a central server or the like over theInternet165 at periodic intervals for consolidation at a central facility.

One advantage of the foregoing system architecture is that it provides a scaleable architecture that may be scaled to deliver a small number of megabits as well as further scaled to deliver nearly a gigabit of content to a large number of host computers. This architecture is only constrained by satellite transponder capacity, which is typically about 30 mbs per transponder.

FIGS. 8a and 8b illustrate the uplink and downlink systems suitable for handling at least 60 mbs. File server stations, such as the one shown atFIG. 4, typically only have a capacity of 30 mbs. As such, the uplink here uses twofile server stations100a and100b. On the uplink side, a second cluster ofserver PCs105 is connected to asecond router110b, which is connected to the uplink equipment and transmits the signal over thesame satellite55 using a different transponder frequency. Alternatively, the transmission of signals from thesecond router110b may be directed to a different satellite than the one used by the firstfile server station100a. If the two signals are uplinked onto the same satellite, then it is possible to share a common antenna.

At the downlink side ofFIG. 8b, there are twoIPMS units120a and120b, which are each identical to that described above. If the two signals are uplinked on the same satellite, it is possible to share anantenna130 on the downlink as shown inFIG. 8b. If not, then two separate antennas are required, one pointing to each of the different satellites. In the scenario shown in8b, the twoIPMSs120a and120b are connected to a100baseT LAN280. The maximum bit-rate delivered to theLAN280 is the sum of the individual bit rates of theIPMSs120a and120b, or about 60 mbs. This is a convenient number since the maximum real capacity of a 100BaseT LAN is about 60 mbs.

Additional file server stations and IPMSs may be added to the foregoing system to increase the number of available multimedia multicast channels available to the ISP clients. For example, a 90 mbs system may be constructed by adding a further file server station at the uplink side of the system and adding a further IPMS at the ISP POP. This third IPMS, however, presents a problem for a 100BaseT LAN since the total possible throughput can now exceed the allowable LAN bandwidth. Thetraffic server255 can be used to assist in eliminating this problem.

At the heart of the multicasting protocol is the fact that generally no unnecessary traffic is forwarded unless someone has requested it. This means that even if there is 90 mbs of total data received from the satellite, there would be no data output to the 100BaseT LAN if there were no clients requesting a connection to it.

On the other hand, it is possible that there could be clients requesting placement of the entire 90 mbs on the LAN. Such traffic would saturate theLAN280. To mitigate the problem, there are at least two potential solutions.

The first solution is to modify the client software so that it first contacts thetraffic server255 to determine how much bandwidth is already delivered to theLAN280. If the LAN is already delivering the maximum possible data to other clients, then the client currently trying to connect is given a message stating that the system is too busy.

A second solution is to have an IPMS first contact thetraffic server255 to check the load on theLAN280 before providing a channel of multicast data on theLAN280. To this end, theIPMS120 contacts thetraffic server255 after a request has been made for a channel of multicast data but before the data is supplied on theLAN280. If thetraffic server255 deems that the load is too high, it instructs theIPMS120 to ignore the join request and refrain from transmitting the requested group on theLAN280. As a result, the requesting client would not receive the requested video/audio stream. The client software may indicate the failure to receive the requested data upon termination of a predetermined time period and indicate this fact to the user. Nevertheless, the applicants believe that there is a high probability that 90 to 120 mbs of data could be uplinked with no downlink overload on the LAN, since it is highly unlikely that all data rates of all channels would be simultaneously used.

The traffic server software could be imbedded into one of the IP Multicast Switches120 and thus eliminate separatetraffic server hardware255. If the system data is scaled even higher, then the architecture shown inFIG. 9 is used at the downlink side of the system. The transmission data rate at the uplink side is obtained by merely adding furtherfile server stations100. The system shown a inFIG. 9 adds a new piece of hardware calledgigabit switch290. On the right side of theswitch290 is a connection to theLAN300. TheLAN300 in this embodiment is capable of handling the total aggregate bandwidth output by allIPMSs120. For the case where eachIPMS120 is receiving 30 mbs and there are 10 IPMSs, then the aggregate bandwidth is 300 mbs. This implies that theLAN300 is capable of handling such traffic.

As further illustrated inFIG. 9, acontroller310 may be used to communicate with theLAN300 and, further, with thedemodulators125 andIPMFs140 over acommunication bus315. Such an architecture allows thecontroller310 to program the specific operational parameters used by the demodulators and IPMFs. Additionally, thedemodulators125 andIPMFs140 may communicate information such as errors. status, etc., to thecontroller310 for subsequent use by thecontroller310 and/or operator of the routing station. Still further, thetraffic server255 may be used to facilitate inter-module communications between theIPMFs140.

The connections between theIPMF140 and theswitch290 may be the 100BaseT connections shown in the previous figures. This implies that theswitch290 requires n-100BaseT input ports to accommodate the n-IPMS inputs. The system proposed inFIG. 9 assumes the use of gigabit access and distribution routers, gigabit LANs and gigabit switches. Such network components are in the very early stages of deployment.

A second architecture that can be used to scale to a large number of a users is shown inFIG. 10 and is similar to the architecture shown inFIG. 9 in that then both include thesatellite demodulators125 and theIP Multicast Filters140. The system ofFIG. 10, however, replaces thetraffic server255 with anIP filter325 and thegigabit switch290 with astandard 100BaseT hub340. Another significant difference between the two architectures is that theInternet access router205 ofFIG. 10 is directly connected to the backbone of the gigabit LAN while the connection for the Internet access by theclients335 is through theIP filter325 within the LAN interface module. TheIP filter325 may be implemented by a PC or the like, or by a microcontroller, TheIP filter325 performs the functions of thetraffic server255 as well as simple IP packet filtering. It passes each packet received from the Internet without examination or modification. This includes multicast as well as unicast traffic. Packets received from thehub340 are examined on a per packet basis. Multicast packets with a group address used by the satellite delivered multicast system (shown here as the Satellite Interface Unit (SIU)) are blocked from traversing onto the Internet. This prevents the Internet Access LAN from overload and serves the function of administratively scoping the multicast traffic to one segment. This architecture also has an added advantage in that the routers used in the domain do not have to be multicast enabled.

The architecture shown inFIG. 10 can be viewed as dividing an ISP into smaller ISP's within the larger ISP. Each of these mini-ISPs has its own IAN Interface Unit (LIU)405. This architecture places a performance requirement on the IP filter in that it must be capable of processing all packets flowing through it via the 100BaseT LANS to which it is connected.

FIG. 11 illustrates a further system architecture that replaces theIP filter325 ofFIG. 10 with atraffic server255 and uses a 10/100BaseT switch410 in place of theIP filter325. This architecture requires the 10/100BaseT switch410 to perform the IP multicast filtering that was done in theIP filter325.

Theinterface point417 ofFIG. 11 between the IPMS and a particular ISP LAN segment, may also be facilitated in cases where that LAN segment is remotely located. Standard digital telecommunications services may be employed to serve as electrical “extension cords” to bring the output of the IPMS onto the remotely located segment. This is done through commonly available “CSU/DSUs” that can transform the LAN output of the IPMS into a digital signal compatible with the Network Interface requirements of common communications carriers, and at the remote location, a subsequent translation back into the required 100BT LAN signal.

FIG. 12 shows one manner of implementing the architectures for the satellite downlink. TheIP Multicast Switch120 can be functionally and physically divided into asatellite interface unit425 and aLAN interface unit430. MultipleLAN interface units430 may be connected to a singlesatellite interface unit425. This allows the satellite reception equipment to be located at a first location and its output distributed to various remotely located LAN interface units. As shown inFIG. 3 the basic system architecture ofFIG. 12 also allows for the distribution of content via an alternate transmission facility such asterrestrial fiber110. Alternatively, these two modules can reside in the same chassis and use the chassis backplane for intermodule communication.

FIG. 14 illustrates an embodiment of the system at an ISP with distributed POPs that are interconnected with one another. This embodiment of the system isolates the multicast traffic from the unicast traffic. Inter-POP multicast traffic is carried on a separate transmission facility.

One embodiment of an IPMS discussed earlier is illustrated inFIGS. 15 and 16. Generally stated, the embodiment of theIPMS unit120 shown here and subsequently described is comprised of acontroller unit440 and one ormore transponder units445. Thecontroller unit440 handles the monitoring, control, and configuration of theIPMS unit120. Thetransponder units445 performs demodulation and de-packetization of the RF signal data received from thesatellite55 and provides the demodulated data to thehub340 of a100BT LAN220 when directed to do so by thecontroller unit440. In some implementations of the system, there may be a need for a splitter unit450 that divides the RF signal for supply toseveral transponder units445.

As noted above, thecontroller unit440 handles all monitor, control, and configuration of theIPMS unit120. It maintains logs of all of the events in the system and processes all incoming TCP/IP protocol messages to theIPMS unit120. These messages include the IGMP join requests from remote clients, individually addressed commands to thecontroller unit440, and packets destined toindividual transponder units445. Thecontroller unit440 is responsible for logging all of the trace type events in a non-volatile memory device, such as ahard disk drive455.

As illustrated, thecontroller unit440 is comprised of amicroprocessor unit460, two network interface cards (NIC)465 and467, amodem470 for connection to a remote port, avideo controller475 for connecting a video monitor, akeyboard interface480 for connection to a keyboard, aDRAM485 for storage, an RS-232port487 for external communications, and thehard drive455.

Themicroprocessor unit460 may be an Intel Advanced ML (MARL) Pentium motherboard. This board has two serial ports, a parallel port, a bus mastering IDE controller, a keyboard interface, a mouse interface, support for up to 128 MB of DRAM, and a socket for a Pentium microprocesser. The board supports 3 ISA extension boards and 4 PCI extension boards. The MARL motherboard is designed to fit into the standard ATX form factor.

The RS-232port487 supports commands from a remote port that can be used for both monitor and control functions. This interface supports standard RS-232 electrical levels and can be connected to a standard personal computer with a straight through DB-9 cable. The software used to implement the interface supports a simple ASCII command set as well as a packet protocol that can be used to send commands that contain binary data.

Monitor and control interface software490 executed by themicroprocessor unit460 supports multiple communications settings for the RS-232port487 by allowing the user to change the baud rate, the number of data bits, the number of stop bits, and the type of parity. These settings are saved in non-volatile memory so that they are preserved after power has been removed from the receiver.

The monitor and control interface software490 preferably supports both a simple ASCII protocol and a more complex packet structure. The ASCII protocol is a simple string protocol with commands terminated with either a carriage return character, a line feed character, or both. The packet protocol is more complex and includes a data header and a terminating cyclic redundancy check (CRC) to verify the validity of the entire data packet.

The ASCII protocol is preferably compatible with a simple terminal program such as Procomm or HyperTerminal. When an external terminal is connected to the RS-232 port47, thecontroller unit440 initially responds with a sign-on message and then displays its “ready” prompt indicating that the is ready to accept commands through the monitor and control interface software490. Commands are terminated by typing the ENTER key which generates a carriage return, a line feed, or both. Thecontroller unit440 interprets the carriage return, as the termination of the command and begins parsing the command.

Most commands support both a query and a configuration form. Configuration commands adhere to the following format:
cmd param1<,param2>CR
where cmd is the command mnemonic, param1 is the first parameter setting, the <,param2> indicates an optional number of parameters separated by commas, and CR is a carriage return.

Queries of commands can be entered in one of two forms as follows:
cmd?CR or optionally
cmdCR
Thecontroller unit440 responds to the query with the command mnemonic followed by the command's current setting(s).

Thecontroller unit440 may also communicate through the monitor and control interface software490 using a predetermined packet protocol. One such protocol is illustrated inFIG. 17. The illustrated protocol is an asynchronous character based master-slave protocol that allows a master controller to encapsulate and transmit binary and ASCII data to a slave subsystem. Packets are delimited by a sequence of characters, known as ‘flags,’ which indicate the beginning and end of a packet. Character stuffing is used to ensure that the flag does not appear in the body of the packet. A 32-bit address field allows this protocol to be used in point-to-point or in point-to-multipoint applications. A 16 bit CRC is included in order to guarantee the validity of each received packet.

Theopening flag500 includes a7E_H01_Hflag pattern indicating the start of packet or end of the packet at510. Atransaction ID505 follows theopening flag500 and is, for example, an 8-bit value that allows the master external computer to correlate thecontroller unit440 responses. The master computer sends an arbitrary transaction ID to thecontroller unit440, and thecontroller unit440 preferably responds with the 1's complement of the value received from the master. Following thetransaction ID505 is a value that allows the master to identify the addressing mode of the packet. This portion of the packet is called the mode byte and is shown at515. These addressing modes include broadcast, physical, and logical modes. Anaddress field520 anddata field525 follow themode byte515. The address field value is used in conjunction with the mode field to determine if the slave should process the packet. Thedata field525 contains information specific to the application. This field can be any size and is only limited by the application. Finally, a CRC-16field530 follows thedata field525. The CRC-16field530 allows each packet to be validated. Each byte from themode byte515 to the last data byte is included in the CRC calculation.

The monitor and control interface software490 supports the same command set as both a remote port and a TCP/IP in-band signaling channel. This allows theIPMS120 to be controlled identically using any of the possible control channels (although the physical connection and physical protocol vary by connection) which provides redundant means of monitor and control. These commands are described in further detail below.

Thecontroller unit440 includes thehard drive455 for its long-term storage. This drive is preferably at least 2.1 GB in size and uses a standard IDE interface. Thedrive455 is preferably bootable and stores the operating system, the application(s) running theIPMS120, and all long-term (non-volatile) data such as history/trace data.

Thenetwork interface card465 is used to communicate with all of thetransponder units445 in theIPMS120. Thenetwork interface card465 is comprised of a 10 based-T LAN interface running standard TCP/IP. Individual commands are issued using the same protocol as set forth above in connection with the monitor and control interface software490 as well as any remote port connected throughmodem470. This protocol is encapsulated into TCP/IP and sent via an internal LAN532 over transmission line535.

Thenetwork interface card465 supports both broadcast and individual card addressing. This interface also supports two-way communication that can be initiated by any unit on the internal LAN532.Individual transponder units445 may communicate with each other over the internal LAN532, although this interface is not truly intended to be used in this fashion in the embodiment shown here. The 10 Based-T interface card465 may be implement using any off-the-shelf network interface card.

Themodem470 of thecontroller unit440 may also support commands that can be used for both monitor and control functions. Themodem470 supports standard phone modem electrical levels and can be connected to a standard phone jack with a straight through RJ-11 cable. Both the ASCII and packet protocols noted above are supported by themodem470. Themodem470 thus provides another communications route to theIPMS120 in case a standard TCP/IP link over the Internet to theIPMS120 fails.

Themodem interface470 is implemented for example, by an off-the-shelf modem and auto-negotiates all communications settings with a Network Operations Center orNOC472 at a location that is remote of the ISP. TheNetwork Operations Center472 preferably uses an identical modem.

TheIPMS120 includes several miscellaneous input and output (IO) functions that are not illustrated inFIGS. 15 and 16. These functions may be handled on either a plug in ISA board or a front panel board. The IO may include status LEDs, a status dry contact closure, and a panic button. The status LEDs may be set through an I/O card. LED indicators may include Power Present, Power OK, Fault, Test, Carrier OK, and LAN Activity. The Power Present LED may indicate that theIPMS120 is plugged into its main AC source. The Valid Power LED may indicate if the power within theIPMS120 is within valid tolerance levels. The Fault LED may indicate if a major fault is occurring in theIPMS120. The Test LED may indicate that theIPMS120 is in a test mode, either its power up test or an on-line test mode. The Carrier LED may indicate that alltransponder units445 that should be acquired (have been programmed to lock onto a carrier) are, in fact, locked. If anysingle transponder unit445 is not locked, this LED will be off. The LAN activity LED may indicate that theIPMS120 has activity on its 100 based-T LAN.

A Form C dry contact closure may be provided to indicate the status of theIPMS120. If theIPMS120 goes into a fault condition, theIPMS120 will provide an output signal along one or more lines at540 to drive closure to a closed state. This provides a means of monitoring the overall operational integrity of theIPMS120 with an external device triggered by the contact closure. Devices that could be used include automatic pagers or alarm bells.

TheIPMS120 may also have a panic button that is used to turn off outgoing multicast video. This will provide the ISP with a quick and efficient way of stopping theIPMS120 data flow onto theISP LAN240 in cases of extreme LAN congestion or a when amalfunctioning IPMS120 inadvertently congests theLAN240. This button preferable will not take thecontroller unit440 link off of the network. This ensures that thecontroller unit440 will still be susceptible to monitoring and control through the TCP/IP port connected to the ISP'sLAN240.

Once the panic button has been pressed, theIPMS120 issues a “LAN shutdown” to everytransponder unit445 through thenetwork interface card465. Theindividual transponder units445 are responsible for shutting their LAN output off.

Controller Unit Software Functionality

The following sections provide a brief overview of one embodiment of the software functionality used to operate thecontroller unit440. This software is preferably developed in accordance with an object-oriented, C++, methodology.

Thecontroller unit440 preferably runs under a Microsoft Windows NT Workstation operating system. This operating system supports all of the networking protocols needed as well as supporting the hardware found in thecontroller unit440.

1. Networking Protocols

The networking protocols discussed above are supported by the operating system. The operating system runs an HTTP server that allows control of thecontroller unit440 through a web browser type of application.

2. Watchdog Process

A hardware watchdog timer counter that must be periodically reset is used in thecontroller unit440. If this counter runs out, it generates an interrupt that reset as thecontroller unit440. In addition to this system level watchdog timer, individual applications may maintain their own versions of watchdog monitoring to ensure that they do not “hang.” In cases where an individual task can restart without affecting the overall system, the task will be restarted. In cases where the system becomes unstable, theentire controller unit440 is preferably restarted in an orderly manner. In either case, an error should be generated and logged in the trace buffer.

3. Software Download

Thecontroller unit440 handles software downloads for itself and for all of the transponder units445: Software downloads are preferably performed using VIP file downloads over the local ISP LAN the240 throughNIC467, from a remote station over themodem interface470, or through the RS-232port487. Before a file is downloaded, VIP server software in thecontroller unit440 verifies that the download is, in fact, a new file. The files are preferable downloaded into a fixed directory structure.

4. Network Configuration Tables

TheNOC472 maintains a series of tables used to configure a network of systems such as the one shown inFIG. 15, each system being linked to theNOC472. These tables may be downloaded using FTP or a predetermined table download command and are used by thecontroller unit440 to configure all of thetransponder units445 and to handle any data rate adaptation required by the system. The tables include a Channel Definition Table (CDT), a Carrier Table (CT), and a Channel Cluster Table (CC).

The Channel Definition Table (CDT) is used to define the location and bandwidth of every channel containing, for example, multimedia content, in the overall system. Each channel of the disclosed embodiment has a unique ID that ranges from 0 to 16K. This ID is the same value as the channel's default low order administratively scoped address bits. For example, channel128 will have a default address of X.Y.0.128, where X and Y are the administratively scoped high order address bytes (239.117 for example). The CDT also provides an indication of the carrier frequency on which a channel can be found. The carriers are assigned a unique ID number that can be converted to a frequency and data rate using the Carrier Table set forth below. The CDT also includes the Channel Cluster ID of the cluster in which the channel appears, if any. The Channel Cluster ID is defined in the Channel Cluster Table section below. Each CDT record preferably uses the following record format:

	Channel ID	(8-bits)
	Transponder Number	(16-bits)
	Data Rate (in Kilobytes)	(16-bits)
	Cluster ID	(16-hits)

The CDT only contains records for defined channels in the overall system. If a channel is not defined, theIPMS120 will assume that the channel has zero bandwidth. The overall table will be represented in the following form:

Table ID	(8-bit)
Number of Channels	(16-bit)
Channel Records	(40-bits per record * number of channels)
CRC	(16 bit)

The Carrier Table (CT) provides a means for identifying all of the carriers being used in the overall system. The records in the CT indicate the satellite transponder ID, the frequency of the carrier, its data rate, and the type of coding that the carrier is using (including scrambling). Thecontroller unit440 provides these parameters to thetransponder units445 to acquire the desired carrier. The CT records also contain information about the satellite that the carrier is transmitted from and the polarity of the receive signal. Thecontroller unit440 uses this information to notify an installer. through, for example, a video terminal attached to thevideo controller475, that multiple dishes are required. Further, the satellite ID is used to determine the azimuth and elevation settings for an antenna that is to receive the carrier transmission from the identified satellite. Each record within the CT preferably has the following format:

	Carrier Number	(16-bits)
	Frequency (in kHz)	(32-bits)
	Data Rate (in Hz)	(32-bits)
	Coding type	(8-bits)
	Polarity	(8-bits)
	Satellite ID	(8-bits)

The overall table format for the CT is as follows:

Table ID	(8-bit)
Number of Carriers	(16-bit)
Carrier Records	(104-bits per record * number of carriers)
CRC	(16-bit)

The Channel Cluster Table (CCT) is used to describe a “cluster” of channels. A cluster of services is defined as a set of multiple channels with the same content but using different data rates. This aspect of the present embodiment of the system is set forth above. The CCT is used to allow a client to receive a channel at a different data rate from the one requested. For example, if a client requests a service at 1 Mb but theLAN240 is congested or thecontroller unit440 is close to its maximum allowable bandwidth on the LAN, thecontroller unit440 can inform the client software (usually a browser plug-in or the like) to switch to another channel in the cluster at a lower data rate, say 500 kb. To facilitate lookup times, each channel has its associated cluster ID in its record within the Channel Definition Table. This allows thecontroller unit440 to easily locate a channel ID, determine its Cluster ID, and find alternate channels. Each Channel Cluster record preferably conforms to the followings record format:

	Cluster ID	(16-hits)
	Number of Channels in Cluster	(8-bits)
	Service ID's channels)	(16-bits * the number of channels)

The overall table format for the CT is as

• • Table ID
  • Number of Clusters
  • Cluster Records
  • CRC
  • (16-bits)
  • (8-bits)
  • (16-bits*the number of follows:
  • (8-bit)
  • (16-bit)
  • (24+(16*the number of channels)*numbers of clusters)
  • (16 bit)

5. Networking Protocols

As discussed above, thecontroller unit440 may receive Internet related protocol messages. It processes such messages and performs the necessary actions to maintain the controller unit environment. For example, when thecontroller unit440 receives an IGMP join message from an end-user client application requesting a new service, it may respond with a predetermined sequence of action. For example, thecontroller unit440 logs the join request, verifies that there is enough bandwidth on theLAN240 to output the service, and sends an Add Service command to theappropriate transponder unit445. Thecontroller unit440 then sends a response back to the client indicating whether or not the join was successful.

6. Inter-IPMS Communications

Thecontroller unit440 communicates with thetransponder units445, and any I/O units that are utilized, through the 10 based-T LAN, shown here at532. The software of thecontroller unit440 maintains a TCP/IP protocol stack to support this interface.

7. Serial Communications Over theModem470 and RS-232Port487

Thecontroller unit440 utilizes the monitor and control software490 described above to handle themodem470 and RS-232port487 serial communications ports. The serial ports are used to send commands to and from thecontroller unit440. The commands supported through this interface are the same as the commands through the 100 based-T LAN interface240.

8. Command Processor

Command processor software tasks handle commands that have come in from the various command channels (modem470,port487, etc.) supported by thecontroller unit440. The commands are parsed and executed as needed.

9. System Event Logging

All significant events may be logged into a trace buffer in, for example, the non-volatile memory (hard drive455). The controller unit software tasks will take an event, timestamp it, and put the resulting string into a trace buffer. The software routines may disable individual events from being put into the log and may control the execution of the logging process (start, stop, reset, etc.).

10. Status Monitoring

A status-monitoring software task in thecontroller unit440 monitors the current status of thecontroller unit440 and periodically polls each of thetransponder units445 for their status. This task maintains an image of the current status as well as an image of past faults that have occurred since the last time a fault history table was cleared (via command). This task further reports fault and status information to theNetwork Operations Center472 over, for example, an Internet connection ormodem470.

11. Statistics Gathering

The statistics gathering task of thecontroller unit440 is similar to the status monitoring software described above. This process keeps track of the number of users “viewing” a particular channel, the addresses of users, the number of collisions on theLAN240, and other long term statistics that may be helpful in monitoring the usage of theIPMS120.

12. Power Up Sequence

The power up sequence software of thecontroller unit440 starts all necessary start-up tasks, determines if thetransponder units445 need to be programmed, performs all needed power up diagnostic functions, and joins the in-band signaling group address of at least on transponder.

13. Dish Pointing Calculation

Thecontroller unit440 supports several antenna pointing aids. For example, thecontroller unit440 provides a ZIP code to azimuth and elevation calculation. This software application takes a ZIP code as an input through, for example, thekeyboard interface480, performs the necessary mathematical calculations or look-up actions, and gives the user the antenna pointing angles needed to find the satellite signal (azimuth and elevation).

14. Interrupts

Thecontroller unit440 uses various software routines in response to interrupt signals. For example, an interrupt may indicate that the watchdog timer has expired and, as such, thecontroller unit440 software begins an orderly soft reset procedure. Thecontroller unit440 also utilizes interrupts to service real time clock, serial port communications, parallel port communications, keyboard interface communications, and mouse interface communications. All of these interfaces generate interrupts that are handled by the operating system.

15. Diagnostics

The controlling unit software supports multiple forms of self-diagnostics. Some of the diagnostics run on power up to verify system integrity, and other diagnostic functions are run periodically while thecontroller unit440 is operational. For example, thecontroller unit440 initially runs several diagnostics including a memory test, a virus scan, a File Allocation Table (FAT) check, a backplane LAN532 connectivity test, and an external 100 based-T LAN240 interface test when power is first supplied. As part of its ongoing monitoring process, thecontroller unit440 also performshard drive455 integrity tests to verify that the file system has not been corrupted. If a hard drive error is encountered, thecontroller unit440 logs the error into its trace history, and tries to correct the problem via downloading of any corrupted files from theNetwork Operations Center472. Still further, thecontroller unit440 monitors the fault status of everytransponder unit445 with which it is associated in therespective IPMS120. The fault monitoring status is an on-going periodic process. All faults are preferably entered into a trace buffer that is available for history tracking. Each fault will be time-stamped and stored in non-volatile memory.

16. Security

The software of thecontroller unit440 supports multiple levels of security, using passwords. The types of levels of access includes ISP monitoring, ISP configuration. network operations monitoring, network operations configuration, and administrative operations. Each level of access has a unique password. The highest levels of authorization will have passwords that preferably change periodically. Any changes to either passwords or configuration settings of thecontroller unit440 preferably requires a confirmation (either in the form of a Yes/No response or another password).

Command Set for Interfacing With theController Unit440

As noted above, commands can be provided to thecontroller unit440 through the RS-232port487, the 100 based-T LANnetwork interface card467, the 10 based-T backplane LAN network,interface card465, or through themodem470. Through the 100 based-T network card467, commands can be issued either through a SNMP interface, an HTTP interface, or raw commands through TCP/IP. Exemplary commands are set forth and described below.

1. TCP/IP Address

The TCP/IP address of theIRMS120 can be set or queried. This command may be sent from an interface other than the LAN connection (since the LAN connectivity depends on this parameter).

2. RS-232 Settings

The settings for the COM port can be either queried or configured through the command interface.

3. Table Download

The network provisioning tables are downloaded via a table download facility. This command is used to process all new tables and reconfigures the system as necessary. The tables are described above.

4. Set Transponder Characteristics (per unit)

Thecontroller unit440 keeps track of whichtransponder unit445 is assigned to each transponder. This implies that the RF parameters of thetransponder units445 are maintained and configured through thecontroller unit440. Once the user has changed a parameter, thecontroller unit440 forwards the changed information to thetransponder unit445 via the backplane of theLAN145.

5. Network Utilization

Several statistics are kept on the network utilization, including the absolute data rate being output onto theLAN220 and the number collisions being encountered on theLAN220. The network utilization statistics may be made available through a “Network Utilization” query command.

6. Maximum LAN Data Rate

The Maximum LAN Data Rate command may be used to limit the amount of bandwidth that thecontroller unit440 uses on theLAN220. This allows the ISP to control the maximum impact that the system has on the LAN backbone.

7. Current Status

Thecontroller unit440 maintains its own internal status and, further, monitors the status of all of thetransponder units445 cards on theLAN145. The current status of theIPMS120, and all of its individual modules, can be queried through the Current Status Command.

8. Card Configuration

The Card Configuration command is used to query the number oftransponder units445 in theIPMS120 and their current settings.

9. Usage Statistics

The Usage Statistics command is used to retrieve the current and past statistics of the channel usage experienced by theIPMS120. This includes the number of viewers per channel, the usage of a given channel per time, the overall usage of the system per time, and the LAN congestion over time. All of these statistics may be made available graphically through an HTTP server or downloaded to the NOC in a binary form using SNMP.

10. Trace

The Trace command is used to start, stop, and configure the trace functions of thecontroller unit440. Individual events can be enabled or disabled to further customize the trace capabilities of theunit440. The trace may be uploaded to theNetwork Operations Center472 for diagnostic purposes. The trace data may be stored on the hard drive, which provides a non-volatile record of the events. The maximum size of the trace log is determined by the available space on the hard disk and, preferably, can be selected by the user.

Thetransponder unit445 is designed to receive, for example, an L-Band signal off of thesatellite55, convert the signal into its original digital form, and put the resulting digital signal onto the ISP's100BT LAN220. EachIPMS120 may includemultiple transponder units445 thereby allowing theIPMS120 to handle significant data traffic.

FIG. 18 illustrates various functional blocks of atransponder unit445. Thetransponder unit445 includes an input550 for receiving an RF signal, such as the L-band signal fromsatellite55. The RF signal is supplied from the input550 to the input of ademodulator555 that extracts the digital data from the RF analog signal. The digital data from thedemodulator555 is optionally supplied to the input of adescrambler560 that decrypts the data in conformance to the manner in which the data was, if at all, encrypted at the transmission site.

One embodiment of adescrambler560 is illustrated inFIG. 19. In the illustrated embodiment thedescrambler560 may be implemented by a field programmable gate array. One type of field programmable gate array technology suitable for this use is a Lattice ISP1016.

Thedescrambler560 preferably automatically synchronizes to the start of a DVB frame marker provided by thedemodulator555. Thedescrambler560 receives digital data from thedemodulator555 alongdata bus565, a clock signal along one ormore lines570, and a data valid signal along one ormore lines575. The data valid signal is used to qualify the clock signal in thedescrambler560. Thedescrambler560 of the illustrated embodiment should have the capability of processing four megabytes/second. Such a processing rate is based on a maximum system data rate of 32 bits/second.

Thedescrambler560 is also provided with a microprocessor interface for programming and monitoring the status of the device by a microprocessor580 (seeFIG. 18) such as a Motorola 860 type processor. Thedescrambler560 preferably supports normal bus access in addition to data transfers through the device into the one packet FIFO. Thedescrambler560 can also issue an interrupt to themicroprocessor580 to request immediate service.

Using amicroprocessor interface585 to thedescrambler560, themicroprocessor580 is provided with access to the internal registers of thedescrambler580 via a bi-directional data bus. Themicroprocessor580 accesses the device's registers via the address bus of the microprocessor interface. Preferably, themicroprocessor580 gains access to the registers of thedescrambler560 using a RDNVR signal qualified by a CS signal consistent with the Motorola 860 bus architecture. Thedescrambler560 can also issue an interrupt to the 860 processor using INT signal. Themicroprocessor580 may also be used to perform overall fuse programming of thedescrambler560 when the descrambler is implemented using a field programmable gate array.

Thedescrambler560 takes the data received on adata bus565 from thedemodulator555, de-scrambles it in a manner consistent with any scrambling operation performed on the data at the transmission site, and provides it to the input of anHDLC controller590. In the illustrated embodiment, thedescrambler560 and theHDLC controller590 interface with one another over anHDLC bus595 that is preferably comprised of an HDLC parallel data bus, a clock signal, and a control bus. TheHDLC controller590 serializes the data received on the data bus of theHDLC bus595 and provides it as a serialized output atserial bus600 for supply at one or more output lines. The serial form of the data is used by theHDLC controller590 for validation and de-packetization operations.

Thedescrambler560 may have two modes of operation: a descramble mode and a clear channel mode. In the descramble mode, the device descrambles the data to be serialized for theHDLC controller590. Preferably, thedescrambler560 supports simple P/N sequenced descrambling. This mode is used as a protected transmission mode that assists in preventing unauthorized access of the transmissions. In this mode, the descrambler may use, for example, an 8 bit seed used to descramble the input data. This seed is preferably programmed into thedescrambler560 through the microprocessor interface bus605. Themicroprocessor580 may asynchronously set the seed value by writing to a seed resister internal to thedescrambler560.

In the clear channel mode, thedescrambler560 allows the data to be serialized without de-scrambling. This mode is used for an unprotected transmission mode in which unauthorized receipt of the transmission is not a significant issue. Clear channel mode can be set by programming the seed register to, for example, all zeros.

Thedescrambler560 may also maintain several counters to allow the microprocessor to detect system errors. For example, thedescrambler560 may store a count of the number of block errors detected. This is preferably implemented as a 16 bit register that rails (i.e. does not cycle back to zero) at 0xFFFF (65,535). Thedescrambler560 stores a count of the number of valid packets read from the IF.

TheHDLC controller590 receives the parallel bit data from the descrambler and depacketizes the HDLC frames. TheHDLC controller590 processes the CRC, removes the flags, and removes any bit stuffing characters from the HDLC frame. If there are any errors in the data they are indicated in the status provided by theHDLC controller590. Typical errors include CRC errors and frames that are too long. The resulting data is fed to aFIFO610 with both start of packet (SOP) and end of packet (EOP) indications. The resulting packets stored inFIFO610 are complete TCP/IP packets that can be output onto the 100BT LAN220 If a packet contains a CRC error, the packet will be discarded and a packet error counter will be incremented.

The data from theFIFO610 is provided to the input of apacket filter615. Thepacket filter615 is preferably implemented using a field programmable gate array. Thepacket filter615 determines whether the data packet stored in theFIFO610 is intended for transmission on theLAN220 or is to be discarded. This decision is made by thepacket filter615 based on whether someone directly connected to theLAN220 or who is remotely connected to theLAN220 has joined the multicast group to which the packet belongs. Thepacket filter615 stores valid packets into asingle packet FIFO620 that is used to buffer the packet for provision to a network interface card, such as anethernet controller625. Theethernet controller625 takes the packet from theFIFO620 and transmits it onto theLAN220 through an ethernet transceiver and transformer using standard ethernet protocols. Such protocols include collision detection and re-transmission as well as all preamble and CRC generation needed. The output of theethernet controller625 is fed, using a standard media independent interface (MII) to anethernet transceiver630 that converts the digital packet into an ethernet analog signal.

Atransformer635 is used to alter the electrical levels of this signal so that it is compatible with theLAN220 Themicrocontroller580 configures and monitors this entire process and reports status, logs faults, and communicates with external systems via the internal 10-basedT backplane LAN145. In addition to thebackplane LAN145, thetransponder unit445 can be controlled through a standard RS-232port637 that, for example, may be used for debuting the unit.

Preferably, thepacket filter615 is a TCP/IP filter implemented using a field programmable gate array. The primary task of thepacket filter615 is to filter all IP packets received and to pass only valid packets for which a subscriber exists on the network for the multicast transmission. Other tasks that may optionally be performed bypacket filter615 are such tasks as IP address translation (see above), notification of the microprocessor of the occurrence of any over flow errors on the channel, etc.

FIG. 20 illustrates one embodiment of thepacket filter615 as implemented by a fieldprogrammable gate array645 and a static RAM650. The figure also illustrates the relationship between thepacket filter615 and other system components. The field programmable gate array may be one such as is available from XILINX, LATTICE, ALTERA, or other FPGA manufacturers.

As illustrated, thepacket filter615 includes amicroprocessor interface655 comprised of a microprocessor data bus, microprocessor address bus, and a microprocessor control bus. Themicroprocessor interface655 provides an interface for programming and monitoring the status of thepacket filter615. The device supports normal bus access in addition to data transfers through the device into the onepacket FIFO610. Thepacket filter615 may also issue an interrupt to themicroprocessor580 to request immediate service.

Themicroprocessor580 accesses the registers of theprogrammable gate array645 through the bidirectional data bus of theinterface655. Selection of which of the registers are accessed is performed by themicroprocessor580 over the address bus of theinterface655. Themicroprocessor580 gains access to the registers over the control bus of theinterface655 using a RDIWR signal that is qualified with a CS signal consistent with the Motorola 860 bus architecture. Any interrupt from thepacket filter615 is also provided over the control bus.

The fieldprogrammable gate array645 also provides anSRAM interface660 for interfacing with SRAM650. This interface is comprised of a data bus, an address bus, and a control bus. Thegate array645 gains access to the registers of the SRAM650 by selecting the appropriate resister over the address bus and providing a OE/WR signal qualified by a CS signal consistent with the SRAM bus architecture.

The fieldprogrammable gate array645 provides packet flow control between theFIFO620 andFIFO610. This control is provided based on a FIFO interface that includes adata bus665 and aFIFO control bus670.

In the disclosed embodiment, thepacket filter615 is designed to store up to 64K (65,535) addresses that are used as filter addresses. The LSB (bottom 16 bits) of the 32-bit address field of a packet is compared to an addresses stored in SRAM650. The addresses in SRAM650 are stored based on commands received by thepacket filter615 from themicroprocessor580. These addresses correspond to multicast group addresses for which a subscriber on the system has issued a “join” command. If the address of a packet received atFIFO610 matches a joined address stored in the SRAM650, then the entire packet will be passed to thesingle packet FIFO610 and theFPGA645 will notify theEthernet controller625 that the data is to be transmitted onto theLAN220. Thesingle packet FIFO610 is used as temporary storage until the entire TCP/IP packet is processed and transmitted to theethernet controller625. If a re-transmit is needed, then thesingle packets FIFO610 is reset and the data can be read again.

Thepacket filter615 auto-synchronizes to the HDLC start of frame marker. This marker is read from theFIFO620 and the ninth hit is used to signal theFPGA645 to re-synchronize the internal state machine.

In the event that theethernet controller625 cannot successfully transmit the packet stored in thesingle packet FIFO610, thepacket filter615 either initiates a re-transmit cycle or aborts the packet and continues with the next available packet. To make this determination, thepacket filter615 queries theFIFO620 for a half-full status. If theFIFO620 is more that half full, then the packet in thesingle packet FIFO610 is discarded. If theFIFO620 is more than half full, then thesingle packet FIFO610 is placed in a re-transmit mode and the packet is given another chance for transmission.

Thepacket filter615 may also include a pass-through mode of operation. In this mode thepacket filter615 allows themicroprocessor580 to write data into thesingle packet FIFO610 for application to theethernet controller625 and, therefrom, for transmission on theLAN220. This mode may be used to send test packets to theethernet controller625 and to the client sub-system.

Thepacket filter615 may maintain several counters to allow themicroprocessor580 to detect system errors. Such counters may include a counter for demodulator block errors, a counter for packet re-transmit errors, a counter for packet abort errors, a counter for valid packet count, and a counter for valid address count. Each of these counters may be reset through commands issued from themicroprocessor580 to thepacket filter615.

The demodulator block error counter is used to count the number of block errors that are detected. This counter may be a 16 bit register that rails at 0xFFFF.

The packet re-transmit error counter stores a count of the number of packets that thepacket filter615 tried to re-transmit. If a packet is retransmitted more than once, each attempt increments the count. This counter is preferably implemented as a 16 bit register that rails at 0xFFFF (65,535).

The packet abort error counter stores a count of the number of packet aborts that have occurred. This is the packets that were not successfully transmitted. This is a 16 bit register that rails (i.e. not cycle back to zero) at 0xFFFF (65,535).

The valid packet counter stores a count of the number of valid packets read fromFIFO620 while the valid address counter stores a count of the number of valid TCP/IP addresses received. Each of these counters is preferably implemented as a 32 bit register counter

Table 1 below describes some of the write registers that may be included in thepacket filter615, while Table 2 (below Table 1) describes some of the read registers that may be included.

TABLE I
WRITE REGISTERS

REGISTER	Size
MNEMONIC	(bits)	Description
RAMADDRH
	8	SRAM addressHigh
RAMADDRL
	8	SRAMaddress Low
RAMDATA
	5	SRAM Data
		Bit 0 - Filter ON/OFF
		Bit
1 . . . 4 - Translation Address (A15 . . . Al2)
		of the TCP/IP address
CONTROLREG
	8	Miscellaneous control register
		Bit 0 - Micro pass-through mode
		Bit 1 - Address Translation ON/OFF
		Bit 2 - unassigned
		Bit 3 - unassigned
		Bit 4 - unassigned
		Bit 5 - unassigned
		Bit 6 - unassigned
		Bit 7 -unassigned
STATREG
	8	Status Register Clear
		Bit 0 - Clear DMERRCNT
		Bit 1 - Clear RETXCNT
		Bit 2 - Clear ABORTCNT
		Bit 3 - Clear PKTCNT
		Bit 4 - Clear ADDRCNT
		Bit 5 - unassigned
		Bit 6 - unassigned
		Bit 7 -unassigned
MACADDR0
	8	Ethernet Controller Address BYTE 0 (LSB)
MACADDR1	8	EthernetController Address BYTE 1
MACADDR2	8	EthernetController Address BYTE 2
MACADDR3	8	EthernetController Address BYTE 3
MACADDR4	8	EthernetController Address BYTE 4
MACADDR5	8	Ethernet Controller Address BYTE 5 (MSB)

TABLE 2
READ REGISTERS

REGISTER	Size
MNEMONIC	(bits)	Description

STATREG

	8	Indicates status of packet filter
		Bit 0 - Input OVERFLOW
		Bit 1 - Single Packet FIFO Timeout
		Bit 2 - Re-Transmit OVERFLOW
		Bit 3 - unassigned
		Bit 4 - unassigned
		Bit 5 -unassigned
PKTSTAT
	16	Last packet transmittedstatus
DMERRCNT
	16	DemodulatorError Count
RETXCNT
	16	Re-Transmit Count
ABORTCNT
	16	Packets Aborted Count
PKTCNT	32	Valid Packets Count
ADDRCNT	32	Valid Packets Count

Table 3 (below) provides an exemplary pin-out listing for the packet filter615:

TABLE 3
	SIZE
PIN NAME(S)	(BITS)	TYPE	DESCRIPTION

MICROPROCESSOR
INTERFACE
DATA
	8	Input/output	Microprocessor
			data bus
ADDRESS
	4	Input	Microprocessor
			data bus
CS
	1	Input	Microprocessor
			chipselect
RW
	1	Input	Microprocessor
			read/write
INT
	1	Output	Microprocessor
			interrupt
FIFO 620
INTERFACE
DATA
	8	Input	FIFOdata input
RD
	1	Output	FIFO read
WR	1	Output	FIFO write
ERR
	1	Input	FIFOblock error
BCLK
	1	Input	FIFObyte clock
BLKSTART
	1	Input	FIFO start ofblock
FULL
	1	Input	FIFOfull flag
HALF
	1	Input	FIFO half full flag
EMPTY	1	Input	FIFO empty flag
SRAM INTERFACE
ADDRESS	16	O	SRAM address
DATA	8	I/O	SRAM data
RW
	1	Output	SRAM read/write
1OE	1	Input	SRAM output enable
SINGLE PACKET
FIFO INTERFACE
DATA
	9	Output	FIFO data
RD
	1	Output	FIFO read
WR	1	Output	FIFO write
RST
	1	Output	FIFO reset
FULL	1	Input	FIFO full flag
EMPTY	1	Input	FIFO empty flag

As noted above, thepacket filter615 may allow each filtered address to be translated into another IP address. Translation is preferably only allowed on the upper nibble of the LSB (A15, A14, A13, and A12). The translation bits will be downloaded along with the address filter information. Still further, thepacket filter615 preferably uses anFPGA645 that is capable of being modified by themicroprocessor580. In such instances, the FPGA technology of theFPGA645 should be chosen to allow local re-programming of the FPGA fuse map.

TheFPGA645 preferably processes at least one mega-words per second (32 bits per word). If theFPGA645 is run at 10 MHz, then 10 internal cycles can be used in a state machine per word received. A shutdown relay or other type of physical device may be employed to shut the 100 based T LAN output off. This may be controlled by themicroprocessor580 and is preferably tied, via backplane communications, to the Panic Button on a front panel of the system. This relay is not shown in the figures.

Thetransponder unit445 of the disclosed embodiment processes a 10 BaseT ethernet connection that necessitates a TCP/IP protocol stack. This stack requirement makes it preferable to use a DRAM in thetransponder unit445. The stack requirement drives the DRAM memory requirements of theunit445. The DRAM should be large enough to support the software (the code will be downloaded into DRAM using a TFTP boot), the RAM variables, and the protocol stacks.

Thetransponder unit445 also preferably includes a battery backed RAM that maintains a small trace buffer, factory test results, and the card's serial number. The non-volatile memory is preferably organized into two identical blocks which are both, individually, subject to CRC checks. Such checks ensure that if a write process is being performed and the power is removed, damaging the integrity of the block, a second backup image of the non-volatile memory will still be intact.

Eachtransponder unit445 preferably includes a test LED, a fault LED, a carrier sync LED, a LAN activity LED, and a LAN collision LED. The test LED is on whenever the unit is performing a test function, including its power up test. The fault LED will be on whenever a major fault has occurred. The carrier sync LED is activated on whenever the RF signal received by thetransponder unit445 is being correctly demodulated and the data is error free.

The LAN activity LED is activated on whenever thetransponder unit445 is actively outputting a multicast stream onto the 100 based-T LAN. The LAN collision LED indicates a collision has occurred on the 100 based T LAN.

Transponder Unit Software Operation

Thetransponder unit445 is preferably controlled by an embedded software application. The software is responsible for configuring the hardware of thetransponder unit445, monitoring all activity of thetransponder unit445, and processing any backplane communications. The following sections describe the various interfaces and tasks that the software supports.

1. Operating System

The underlying real time operating system (RTOS) is preferably VxWorks. VxWorks has been used in embedded processor designs for over 18 years and provides a preemptive operating environment with an integrated protocol stack and other types of networking support.

2. Backplane Host Interface

The host interface over the backplane is implemented on a 10 based-T ethernet LAN145 and the LAN protocol is TCP/IP. All commands that are issued over thebackplane LAN145 are processed identically to commands received over the RS-232serial interface487. Thecontroller unit440 transmits commands to thetransponder unit445 over this interface. Still further, thecontroller unit440 passes commands from theNOC472 to thetransponder unit445. In order, to support this interface, the operating system's standard networking protocols are used.

3. RS-232 Serial Command Interface

Theserial port637 is used to provide a diagnostic port that can be used to send commands to thetransponder unit445. The serial port software processes commands identically to the backplane host interface.

4. Command Processor

The command-processing task parses incoming commands and executes any actions specified by the command.

The following sections (A-N) describe some example commands that thetransponder unit445 supports:

A. Add Group

The Add Group command allows thecontroller unit440 to enable a group address to be passed through to the 100 based-T LAN220. When this command is executed, the microcontroller640 enables the group's address within the lookup table in the SRAM650.

B. Delete Group

The Delete Group command allows thetransponder unit445 to disable a group address that is currently being passed through to the 100 based-T LAN220. When this command is executed, themicrocontroller655 disables the group's address within the lookup table in the SRAM650.

C. Address Route

The Address Route command is used to change the default IGMP address of a particular service or block of services. As described previously, the entire address block allocated to the video from the satellite can be moved or individual channel addresses can be moved. Thetransponder unit445 is programmed with an address map and programs the FPGA650 accordingly.

D. LAN Shutoff

The LAN shutoff command activates a relay on the output to the 100 based-T LAN220 Thecontroller unit440 issues this command when the Panic Button has been pressed.

E. RS-232 Port

The RS-232 Port command is used to change the communication port parameters. These parameters include the baud rate, parity bit, stop bit, and number of data bit settings for the port.

F. Boot

A TFTP process, initiated by the operating system of thetransponder unit445 will handle the boot process. This process is handled over thebackplane LAN145.

G. Status and Fault

The current status and fault histories can be queried through the Status and Fault commands. These commands are accessed by thecontroller unit440, theNOC472, and through the RS-232port675 to determine the status and fault histories of thetransponder unit445.

H. Trace

Similar to the trace command on thecontroller unit440, the trace command of thetransponder unit445 can be used to configure (start, stop, or reset) the trace buffer, or it can be used to query the contents of a trace buffer. The trace buffer on thetransponder unit445 may be implemented to be much smaller than the trace buffer of thecontroller unit440 so thecontroller unit440 accesses data from the trace buffer of thetransponder unit445 periodically, resetting the trace after the query is complete.

I. Set Carrier

The Set Carrier command is used to set the L-Band frequency and data rate of thedemodulator555. Once this command has been issued, thetransponder unit445 begins its acquisition process.

J. Scrambler Bypass

The Scrambler Bypass command allows thetransponder unit445 to pass data through the system that has not been scrambled at the head end. This mode is used during development, testing, and may be used in operation.

K. Reset

The Reset command allows an external source, such as thecontroller unit440, theNOC472, or a terminal attached the RS-232 port to initiate a soft reset on thetransponder unit445.

L. ID Query

Eachtransponder unit445 will have a unique serial number associated with it. The serial number will be stored in non-volatile memory. The ID Query command is used to either query or set the serial number. When setting the serial number, the command is preferably sufficiently scrambled to prevent the serial number from being inadvertently programmed to an incorrect value.

M. Memory Read and Memory Write

The Memory Read and Memory Write commands are used primarily for development and allows any hardware register or memory location to be manipulated manually. This includes being able to toggle LED's, update the seven-segment LED, or other I/O based activities.

N. Test Mode

The Test Mode command provides a means of putting various components of thetransponder unit445 into test modes. For example, one test mode generates test packets onto the 100 based-T output LAN. These packets include a packet counter which can be used by a client application to determine if the link is experiencing dropped packets. This command may also be used during board level testing with the results of the production tests stored in nonvolatile memory.

Thetransponder unit445 is also provided with a number of diagnostic functions that support both power up and long-term diagnostic functions. On power up, all hardware subsystems are tested including the DRAM, the non-volatile memory, communications with the demodulator, and backplane ethernet connectivity. Long term diagnostic functions include validating the code space (CRC check of the code space), validating the non-volatile memory, and validating backplane connectivity.

On powering up, the operating system of thetransponder unit445 boots from its core from EPROM. After this, thetransponder unit445 requests its current version of firmware from thecontroller unit440 using a Trivial File Transfer Protocol (TFTP). This method of booting thetransponder unit445 ensures that all transponder units in the IPMS chassis are running the same version of software. The operating system, as noted above, supports this type of boot procedure. Once the code has been downloaded, the code begins executing.

Thetransponder unit445 also includes a status and fault monitoring task that keeps track of the current status as well as a fault history value that indicates all of the faults that have occurred since the last time the fault history was cleared. When the status of thetransponder unit445 changes, a trace event is logged into the non-volatile memory of thetransponder unit445 and thecontroller unit440 is notified that thetransponder unit445 has at least one event saved in its non-volatile memory. Since thecontroller unit440 preferably maintains a much larger trace buffer than thetransponder unit445, thecontroller unit440 is responsible for pulling data out of the log of thetransponder unit445 prior to overflow thereof.

Thetransponder unit445 also includes an internal watchdog timer. If the internal watchdog timer has expired, thetransponder unit445 assumes that its internal software has reached an unstable condition. As such, thetransponder unit445 will shutdown all current tasks and then reset. The reset re-initializes thetransponder unit445 and begins a re-boot procedure. Thetransponder unit445 will preferably log this event in non-volatile memory. Thecontroller unit440 recognizes this condition, logs an error, and reconfigures thetransponder unit445.

Thetransponder unit445 shuts down the outgoing IGMP streams after thebackplane LAN145 becomes inoperable for a specified period of time. If thebackplane LAN145 has become inoperable, thetransponder unit445 assumes that thecontroller unit440 has ceased operation. Since thecontroller unit440 is responsible for all of the protocol communication of theIPMS120 with external devices, thetransponder unit445 assumes that thecontroller unit440 can no longer receive ‘leave’ requests from clients. In order to prevent “bombarding” the client with potentially unwanted data, thetransponder unit445 will shutdown all outgoing streams.

Oncebackplane LAN145 communications are restored, thetransponder unit445 will request its current channel mapping and begin transmitting again. Thetransponder unit445 logs this event in non-volatile memory.

Eachtransponder unit445 is preferably implemented on a single printed circuit card having the ability to be “hot swapped”. In order for this to be implemented, the connectors between the printed circuit card and its corresponding backplane connector include longer pins for the power and grounds signals such that the transponder unit on the printed circuit board has power applied to it before output signals reach the connectors of the backplane bus.

A “hot sparing” system can also be employed. In such instances, one or more spare transponder units are included in theIPMS120 chassis. The spare transponder units can be configured to take over for failed transponder units. This configuration procedure will be handled by the controller unit via thebackplane LAN145.

TheIPMS120 may have several means of helping an installer point the antenna. To this end, eachtransponder unit445 provides an AGE indication that provides a means of identifying when the satellite signal is maximized. This indication alone will not necessarily provide the best signal, however, due to different types of interference (adjacent satellite, cross-pole, etc.). Many times the interference should be minimized instead of the signal level being maximized. To aid in this type of decision making eachtransponder unit445 will provide an Eb/No reading that indicates the quality of the incoming signal. This measurement should be maximized. The values of these parameters will be passed to thecontroller unit440, which can present them in a user-friendly manner to the installer. This data may also be available through theserial port637 of thetransponder unit445.

As also illustrated inFIG. 18, thetransponder unit445 also includes a 10baseT connection to the controller unit. This interface includes anethernet transceiver672 andtransformer673. It should be furthered noted that substantially all of the principal units of thetransponder unit445 communicate withmicroprocessor580 over a communications bus.

FIGS. 21-26 illustrate various example ISP configurations and scenarios using theIPMS120 of the present invention. In each scenario, an IP Multicast system application delivers IP multicast streams to Internet Service Providers' (ISPs) clients. The stream content is received, for example, over a satellite by the IPMS which is directly attached to an ISP's local backbone. The stream flows over the local backbone and through the ISP's networking equipment to the client's desktop browser as shown, for example, atarrow680 ofFIG. 21.

There are a number of goals for each of the following ISP configurations and scenarios. They include:

• • Delivering streams to clients on demand, and quickly removing these streams from the ISP backbone when the client is finished
  • Delivering streams to clients while minimizing the traffic on the local backbone of the ISP;
  • Delivering streams to clients while minimizing additional traffic to other clients: and
  • Delivering streams to clients while not introducing any additional traffic to the Internet.

Achieving these goals requires that the networking equipment utilized in the system support various protocol interactions (e.g. IP, IGMP, PIM).

ISP Model 1—Simple ISP (Simple IPMS120)

ISP MODEL1 is illustrated inFIG. 21. In this example Client A joins, receives, and leaves Multicast Group 239.216.63.248 from theIPMS120. Next, Client A joins and receives Multicast Group 239.216.0.8. Then, network elements query the group so that multicast traffic can be pruned in the event group members silently leave the group. Finally, Client A leaves Multicast Group 239.216.0.8.

TheIPMS120 filters the multicast stream so that which are currently “joined will be placed on the ISP LAN several assumptions associated with scenario, they are:

• • IPMS120 IP Address128.0.0.255, Client AIP Address=128.0.0.1:
  • All IP Multicast Addresses provided by theIPMS120 are “Administratively Scoped” addresses in the range 239.216.0.0 through 239.219.255.255 (addresses 239.216.0.8 and 239.216.63.248 used in this example); and
  • IPMS120. Access Switch/Routers #1 and #2, andGateway Router685 support IGMP V2.

During initial handshake, the following occurs:

• • 1. Client A sends an IGMP V2 Membership Report (Destination IP address=239.216.63.248, Group address=239.216.63.248);
  • 2. Access Switch/Router #1 forwards IGMP V2 Membership Report to backbone LAN220 (assuming it has no other interfaces in Group address=239.216.63.248);
  • 3. Gateway Router does not forward “Administratively Scoped” membership report to the internet;
  • 4.IPMS120 receives IGMP V2 Membership Report and transmits 239.216.63.248 multicast onto Filtered Stream—the data payload of the 239.216.63.248 multicast includes the IPMS IP Address, and a test pattern;
  • 5. Access Switch/Router #1 forwards 239.216.63.248 multicast to Client A only;
  • 6. Gateway Router ignores 239.216.63.248 multicast as an administratively scoped address;
  • 7. Client A receives IPMS IP Address and test pattern and then sends an IGMP Leave Group (Destination IP address=224.0.0.2, Group address=239.216.63.248);
  • 8. Access Switch/Router #1 verifies it has no other interfaces in Group address=239.216.63.248 (using IGMP Query), forwards IGMP Leave Group toLAN backbone220, and immediately stops forwarding the 239.216.63.248 multicast to Client A;
  • 9.Gateway Router685 ignores IGMP Leave Group command; and
  • 10.IPMS120 receives IGMP Leave Group, verifies it has no other clients in Group address=239.216.63.248 (using IGMP Query), and immediately stops transmission of the 239.216.63.248 multicast data.

When Client A joins Multicast Group 239.216.0.8, the following occurs:

• • 11. Client A sends an IGMP V2 Membership Report (Destination IP address=239.216.0.8, Group address=239.216.0.8);
  • 12. Access Switch/Router #1 forwards IGMP V2 Membership Report to LAN backbone220 (assuming it has no other interfaces in Group address=239.216.0.8);
  • 13. Gateway Router ignores IGMP V2 Membership Report for “Administratively Scoped” address;
  • 14.IPMS120 receives IOMP V2 Membership Report and transmits 239.216.0.8 multicast onto Filtered Stream:
  • 15. Access Switch/Router #1 forwards 239.216.0.8 multicast to Client A only;
  • 16. Gateway Router ignores 239.216.0.8 multicast as an administratively scoped address;
  • 17 Client A receives 239.216.0.8 multicast.

In order to ensure that Client A has not silently left the multicast group, the system implements a querying of the Multicast Group 239.216.0.8 based on query timers configured in the access switch/router andIPMS120. This query proceeds in the following manner;

• • 18. Access Switch/Router #1 sends IGMP Group-Specific Query (Destination IP address=239.216.0.8, Group address=239.216.0.8) to Client A;
  • 19. If Access Switch/Router #1 receives an IGMP V2Membership Report (Destination IP address=239.216.0.8, Group address=239.216.0.8), do nothing;
  • 20. If there is no Membership Report then Access Switch/Router #1 sends IGMP Leave Group (Destination IP address=224.0.0.2, Group address=239.216.0.8) to theLAN backbone220 and immediately stops forwarding the 239.216.0.8 multicast to all clients (including Client A): system operation then proceeds with Step 26 below.

The followings steps occur independently:

• • 21.IPMS120 sends IGMP Group-Specific Query (Destination IP address=239.216.0.8, Group address=239.216.0.8);
  • 22. IfIPMS120 receives an IGMP V2 Membership Report (Destination IP Address=239.216.0.8; Group Address=239.216.0.8) do nothing;
  • 23. If there is no Membership Report thenIPMS120 immediately stops transmission of 239.216.0.8 multicast (group left due to no response);

The following sequence of events occur when Client A leaves the Multicast Group 239.216.0.8;

• • 24. Client A sends an IGMP Leave Group(Destination IP Address=224.0.0.2, Group Address=239.216.0.8);
  • 25. Access Switch/Router #1 receives IGMP Leave Group, verifies it has no other interfaces in Group Address=239.216.0.8 (using IGMP Query), forwards IGMP Leave Group toIAN backbone220, and immediately stops forwarding the 239.216.0.8 multicast to Client A;
  • 26. Gateway Router ignores IGMP Leave Group command since it involves an administratively scoped address;
  • 27.IPMS120 receives IGMP Leave Group, verifies it has no other Clients in Group Address=239.216.0.8 (using IGMP Query), and immediately stops transmission of 239.216.0.8 multicast.

ISP Model2—ISP with Multiple LAN Segments/Multicast

In the example shown inFIG. 22, Client A joins, receives, and leaves Multicast Group 239.216.63.248 to receive a brief multicast from theIPMS120. Next, Client A joins and receives Multicast Group 239.216.0.8. Then, network elements query the group so that multicast traffic can be pruned in the event group members silently leave the group. Finally, Client A leaves Multicast Group 239.216.0.8.

TheSimple IPMS120 filters the Multicast Steam so that only Multicast Addresses which are currently “joined” will be sent to the LAN Switch. The LAN Switch filters the Multicast Stream sent to each segment so that only Multicast Addresses which are currently “joined” by Clients on a segment will be placed on that segment.

There are several assumptions associated with the illustrated scenario.

They are:

• • IPMS120 IP Address=128.0.0.255, Client AIP Address=128.0.0.1;
  • All IP Multicast Addresses transmitted by theIPMS120 are “Administratively Scoped” addresses in the range 239.216.0.0 through 239.219.255.255 (addresses 239.216.0.8 and 239.216.63.248 used in this example);
  • Access Switch/Router, LAN Switch, andIPMS120 support IGMP V2;
  • LAN Switch configuration:
    • Virtual LAN#1=LAN Segment #1, Backbone,IPMS120 Control, FilteredStream#1
    • Virtual LAN#2=LAN Segment #2, Backbone,IPMS120 Control, FilteredStream#2
  • Gateway Router690 does not forward IGMP messages with “Administratively Scoped” Multicast addresses (this includes messages with Dest IP239.*.*.*, and IGMP messages with Dest IP224.0.0.1/224.0.0.2 that specify a Group Address=239.**.*).

During initial handshake, the following occurs:

• • 1. Client A sends an IGMP V2 Membership Report (Destination IP Address=239.216.63.248, Group Address=239.216.63.248);
  • 2. Access Switch/Router #1 forwards IGMP V2 Membership Report to LAN Segment #1 (assuming it has no other interfaces in Group Address=239.216.63.248);
  • 3. LAN Switch receives IGMP V2 Membership Report, forwards the message, and enables transmission of 239.216.63.248 multicast toLAN Segment #1;
  • 4. Gateway Router does not forward “Administratively Scoped” membership report to the Internet;
  • 5.IPMS120 receives IGMP V2 Membership Report and transmits 239.216.63.248 multicast outNIC#2 onto Filtered Stream—the data payload of the 239.216.63.248 multicast includes theIPMS120 IP Address, and a test pattern;
  • 6. LAN Switch forwards 239.216.63.248 multicast toLAN Segment #1 only;
  • 7. Access Switch/Router #1 forwards 239.216.63.248 multicast to Client A only;
  • 8. Client A receivesIPMS120 IP Address and test pattern and then sends an IGMP Leave Group(Destination IP Address=224.0.0.2, Group Address=239.216.63.248);
  • 9. Access Switch/Router #1 receives IGMP Leave Group, verifies it has no other interfaces in Group Address=239.216.63.248 (using IGMP Query), forwards IGMP Leave Group toLAN Segment #1 and immediately stops forwarding the 239.216.63.248 multicast to Client A;
  • 10. LAN Switch receives IGMP Leave Group, forwards the message, verifies that it has no otherLAN Segment #1 Clients in Group Address=239.216.63.248 (using IGMP Query), and immediately stops transmission of 239.216.63.248 multicast toLAN Segment #1;
  • 11. Gateway Router ignores IOMP Leave Group since it is an administratively scoped address;
  • 12.IPMS120 receives IGMP Leave Group, verifies it has no other client in Group Address=239.216.63.248 (using IGMP Query), and immediately stops transmission of the 239.216.63.248 multicast.

When Client A joins the Multicast Group 239.216.0.8, the following operations occur:

• • 13. Client A sends an IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8);
  • 14. Access Switch/Router #1 forwards IGMP V2 Membership Report to LAN Segment #1 (assuming it has no other interfaces in Group Address=239.216.63.248);
  • 15. LAN Switch receives IGMP V2 Membership Report, forwards the message, and enables transmission of239.216.0.8 multicast toLAN Segment #1;
  • 16. Gateway Router ignores IGMP Leave Group since it is an administratively scoped address;
  • 17.IPMS120 receives IGMP V2 Membership Report and transmits 239.216.0.8 multicast outNIC#2 onto Filtered Stream;
  • 18. LAN Switch forwards 239.216.0.8 multicast toLAN Segment #1 only;
  • 19. Access Switch/Router #1 forwards 239.216.0.8 multicast to Client A only; and
  • 20. Client A receives 239.216.0.8 multicast.

In order to ensure that Client A has not silently left the multicast group, the system implements a querying of the Multicast Group 239.216.0.8 based on query timers configured in the access switch I router andIPMS120. This query, proceeds in the following manner;

• • 21. Access Switch/Router #1 sends IOMP Group-Specific Query (Destination IP Address 239.216.0.8, Group Address=239.216.0.8) to Client A;
  • 22. If Access Switch/Router #1 receives an IGMP V2 Membership Report(Destination IP Address=239.216.0.8, Group Address=239.216.0.8), do nothing;
  • 23. If there is no Membership Report then Access Switch/Router #1 sends IGMP Leave Group(Destination IP Address=224.0.0.2, Group Address=239.216.0.8) toLAN Segment #1 and immediately stops forwarding the 239.216.0.8 multicast to all clients (including Client A): and operations then proceed at Step 32.

The following steps occur independently:

• • 24. LAN Switch sends IGMP Group-Specific Query (Destination IP address 239.216.0.8, Group Address 239.216.0.8) toLAN Segment #1;
  • 25. If LAN Switch receives IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8) do nothing;
  • 26. If there is no Membership Report then LAN Switch sends IGMP Leave Group (Destination IP Address=224.0.0.2, Group Address=239.216.0.8) toIPMS120 and immediately stops transmission of 239.16.0.8 multicast to LAN Segment #1 (group is left due to no response);
  • 27.IPMS120 sends IGMP Group-Specific Query (Destination IP Address=239.216.0.8, Group Address=239.216.0.8);
  • 28. IfIPMS120 receives IOMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8), do nothing; and
  • 29. If there is no Membership Report thenIPMS120 immediately stops transmission of 239.216.0.8 multicast (group left due to no response).

The following sequence of events occur when Client A leaves the Multicast Group 239.216.0.8:

• • 30. Client A sends an IGMP Leave Group (Destination IP Address=224.0.0.2, Group Address=239.216.0.8);
  • 31. Access Switch/Router1 receives IOMP Leave Group, verifies it has no other interfaces in Group Address=239.216.0.8 (using IGMP Query), and forwards IGMP Leave Group toLAN Segment #1 and immediately stops forwarding the 239.216.0.8 multicast to Client A;
  • 32. LAN Switch receives IGMP Leave Group, forwards the message, verifies it has no otherLAN Segment #1 Clients in Group Address=239.216.0.8 (using IGMP Query), and immediately stops transmission of 239.216.0.8 multicast toLAN Segment #1;
  • 33. Gateway Router ignores IOMP Leave Group since it is an administratively scoped address;
  • 34.IPMS120 receives IGMP Leave Group, verifies it has no other Clients in Group Address=239.216.0.8 (using IGMP Query), and immediately stops transmission of 239.216.0.8 multicast.

ISP Model3—Large ISP with Affiliated ISP

The system ofFIG. 23 provides multicast streams to all ISP Clients and Remote ISP Clients on demand. In this example. Remote LSD Client H joins, receives, and leaves Group 239.216.63.248 to receive a brief multicast from theIPMS120. Next, Client H joins and receives Multicast Group 239.216.0.8. Then, network elements query the group so that multicast traffic can be pruned in the event group members silently leave the group. Finally, Client H leaves Multicast Group 239.216.0.8.

TheSimple IPMS120 filters the Multicast Stream so that only multicast addresses that are currently joined” will be sent to theLAN Switch695. TheLAN Switch695 filters the multicast stream sent to each segment so that only multicast addresses which are currently “joined” by clients on a LAN segment will be placed on the LAN segment. For the Remote ISP, the multicast streams do not use bandwidth on the Router link to the ISP (to avoid impacting normal Internet traffic). Accordingly, a bridgedconnection700 is used to send the streams to the Remote ISP. The only segments that receive the multicast streams areLAN Segment #1 and the bridgedconnection700 to the Remote ISP that is considered to beLAN Segment #2.

There are several assumptions associated with the illustrated scenario, such as, for example:

• • IPMS120 IP Address=128.0.0.255, Client H IP Address=128.0.0.8;
  • All IP Multicast Addresses transmitted by theIPMS120 are “Administratively Scoped” addresses in the range 239.216.0.0 through 239.219.255.255 (addresses 239.216.0.8 and 239.216.63.248 used in this example);
  • Access Switch/Routers, LAN Switches, andIPMS120 support IGMP V2;
  • LAN Switch configuration:Virtual LAN#1=LAN Segment #1. Backbone,IPMS120 Control, FilteredStream#1;Virtual LAN#2=LAN Segment #2,IPMS120 Control, FilteredStream#2; andvirtual LAN#3=LAN Segment #3, Backbone.
  • LAN Bridge configuration: Only forward 239.216.0.0-239.219.255.255; 224.0.0.1, 224.0.0.2;
  • Remote Router does not forward IGMP messages with “Administratively Scoped” Multicast addresses (this includes messages with Destination IP=239.*.*.*, and IGMP messages with Destination IP=224.0.0.1/224.0.0.2 that specify a Group Address=239.*.**)

During initial handshake, the following occurs:

• • 1. Client H sends an IGMP V2 Membership Report (Destination IP Address=239.216.63.248, Group Address=239.216.63.248);
  • 2. Access Switch/Router #2 forwards IGMP V2 Membership Report to Remote Backbone (assuming, it has no other interfaces in Group Address=239.216.63.248) seminal LAN Bridge forwards IGMP V2 Membership Report;
  • 3. Remote Router ignores IGMP V2 Membership Report as an administratively scoped address
  • 4. LAN Switch receives IOMP V2 Membership Report, forwards the message, and enables transmission of 239.216.63.248 multicast toLAN Segment #2.
  • 5.IPMS120 receives IGMP V2 Membership Report and transmits 239.216.63.248multicast outNIC#2 onto Filtered Stream—the data payload of the 239.216.63.248 multicast includes theIPMS120 IP Address, and a test pattern;
  • 6. LAN Switch forwards 239.216.63.248 multicast toLAN Segment #2 only;
  • 7. LAN Bridge forwards the 239.216.63.248 multicast data;
  • 8. Access Switch/Router #2 forwards 239.216.63.248 multicast to Client H only;
  • 9. Remote Router ignores 239.216.63.248 multicast data;
  • 10. Client H receivesIPMS120 IP Address and test pattern and then sends an IGMP Leave Group (Destination IP Address=224.0.0.2, Group Address=239.216.63.248);
  • 11. Access Switch/Router #2 receives IGMP Leave Group, verifies it has no other interfaces in Group Address=239.216.63.248 (using IGMP Query),
  • 12. Forwards IGMP Leave Group to LAN Bridge, and immediately stops forwarding the 239.216.63.248 multicast to Client H;
  • 13. LAN Bridge forwards IGMP Leave Group;
  • 14. Remote Router ignores IGMP Leave Group as an administratively scoped address
  • 15. LAN Switch receives IGMP Leave Group, forwards the message, verifies it has no other LAN Segment an Clients in Group Address=239.216.63.248 (using IOMP Query), and immediately stops transmission of 239.216.63.248 multicast toLAN Segment #2;
  • 16.IPMS120 receives IGMP Leave Group, verifies it has no other Clients in Group Address=239.216.63.248 (using IGMP Query), and immediately stops transmission of the 239.216.63.248 multicast:

When Client H joins the Multicast Group 239.216.0.8, the following actions occur:

• • 17. Client H sends an IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8);
  • 18. AccessSwitch Router #2 forwards IGMP V2 Membership Report to Remote Backbone (assuming it has no other interfaces in Group Address=239.216.0.8);
  • 19. LAN Bridge forwards IGMP V2 Membership Report;
  • 20. Remote Router ignores IGMP V2 Membership Report as an administratively scoped address;
  • 21. LAN Switch receives IOMP V2 Membership Report, forwards the message, and enables transmission of 239.216.0.8 multicast toLAN Segment #2;
  • 22.IPMS120 receives IGMP V2 Membership Report and transmits 239.216.0.8 multicast outNIC#2 onto Filtered Stream;
  • 23. LAN Switch forwards 239.216.0.8 multicast toLAN Segment #2 only;
  • 24. LAN Bridge forwards the 239.216.0.8 multicast;
  • 25. Access Switch/Router #2 forwards 239.216.0.8 multicast to Client H only;
  • 26. Remote Router ignores 239.216.0.8 multicast
  • 27. Client H receives 239.216.0.8 multicast.

In order to ensure that Client H has not silently left the multicast group, the system implements a querying of the Multicast Group 239.216.0.8 based on query timers configured in the access switch I router andIPMS120. This query proceeds in the following manner:

• • 28. Access Switch/Router #2 sends IGMP Group-Specific Query (Destination IP address=239.216.0.8, Group Address=239.216.0.8) to Client H;
  • 29. If Access Switch/Router #2 receives an IGMP V2 Membership Report (Destination IP Address=239.116.0.8, Group Address=239.216.0.8), do nothing;
  • 30. If there is no Membership Report then Access Switch/Router #2 sends JGMP:
  • Leave Group (Destination IP Address=224.0.0.2, Group Address=239.216.0.8) to Remote Backbone and immediately stops forwarding the 239.216.0.8 multicast to Client H, operations then proceed to Step 40.

The following steps occur independently:

• • 31. LAN Switch sends IGMP Group-Specific Query (Destination IP Address 239.216.0.8, Group Address=39.216.0.8) toLAN Segment #2;
  • 32. LAN Bridge forwards IGMP Group-Specific Query;
  • 33. If LAN Switch receives an IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8), do nothing;
  • 34. If there is no Membership Report then LAN Switch immediately stops transmission of 239.216.0.8 multicast to LAN Segment #2 (group is left due to no response);
  • 35.IPMS120 sends IGMP Group-Specific Query (Destination IP Address=239.216.0.8, Group Address=239.216.0.8)
  • 36. IfIPMS120 receives IGM V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8), do nothing;
  • 37. If there is no Membership Report thenIPMS120 immediately stops transmission of 239.216.0.8 multicast (group left due to no response).

The following sequence of operations occur when Client H leaves Group address=239.216.0.8:

• • 38. Client H sends an IGMP Leave Group (Destination IP Address=224.0.0.2, Group Address=239.216.0.8);
  • 39. Access Switch/Router receives IGMP Leave Group, verifies it has no other interfaces in Group Address=239.216.0.8 (using IGMP Query), and forwards IGMP Leave Group to Remote Backbone and immediately stops forwarding the 239.216.0.8 multicast to Client H.
  • 40. LAN Bridge forwards IGMP Leave Group;
  • 41. Remote Router ignores IOMP Leave Group since it is an administratively scoped address;
  • 42. LAN Switch receives the IGMP Leave Group command, forwards the message, verifies it has no otherLAN Segment #2 Clients in Group Address=239.216.0.8, and immediately stops transmission of 239.216.0.8 multicast toLAN Segment #2;
  • 43.IPMS120 receives IOMP Leave Group, verifies it has no other Clients in Group Address=239.216.0.8 (using IGMP Query), and immediately stops transmission of the 239.216.0.8 multicast.

If Remote Clients join “normal” multicast groups (i.e., those transmitted over the backbone of the Internet) through the Remote Router, the 224.0.0.1 and 224.0.0.2 IGMP V2 messages will be bridged to the LAN Switch. The LAN Switch forwards the IGMP messages throughLAN segment #2 to theIPMS120. TheIPMS120 ignores the messages issued for a non-existent stream.

ISP Model4—Simple ISP Scenario2

In the scenario ofFIG. 24. Client A and theIPMS120 first join Multicast Group 239.216.63.240 to establish a mechanism for sending multicast control messages to each other. Next, Client A joins, receives, and leaves Multicast Group 239.216.63.248 to receive a brief multicast from theIPMS120. After that, Client A joins and receives Multicast Group 239.216.0.8. Then, network elements query the group so that multicast traffic can be pruned in the event group members silently leave the group. Finally, Client A leaves Multicast Group 239.216.0.8. As above,IPMS120 filters the multicast stream so that only multicast addresses which are currently ‘joined’ are provided on the backbone of the LAN.

In this scenario, several assumptions have been made. They, are:

• • IPMS120 IP Address=128.0.0.255, Client A IP Address=128.0.0.1;
  • All IP Multicast Addresses transmitted by theIPMS120 are “Administratively Scoped” addresses in the range 239.216.0.0 through 239.219.255.255 (addresses 239.216.0.8, 239.216.63.24 through 239.216.63.248 being used in this example);
  • IPMS120, Access Switch/Routers, and Gateway Router support IGMP V2 protocol;
  • TheIPMS120 and the clients use MulticastAddress=239.216.63.240 to pass proprietary UDP packets using is UDP Port=255.

The following operations occur during initial handshake:

• • 1.IPMS120 sends an IGMP V2 Membership Report (Destination P Address=239.216.63.240, Group Address 239.216.63.240);
  • 2. The 239.216.63.240 multicast will be used for multicast control messages;
  • 3. Gateway Router does not forward “Administratively Scoped” membership report to the Internet;
  • 4. Client A sends an IGMP V2 Membership Report (Destination IP Address=239.216.63.240, Group Address=239.26.63.240);
  • 5. Access Switch/Router #1 forwards IOMP V2 Membership Report to LAN Segment#1 (assuming it has no other interfaces in Group Address=239.216.63.240);
  • 6. LAN Switch receives IGMP V2 Membership Report, forwards the message, and adds Client A to the Group;
  • 7. Gateway Router does not forward “Administratively Scoped” membership report to the Internet;
  • 8.IPMS120 receives IGMP VI Membership Report; the 239.216.63.240 multicast will be used for multicast control messages;
  • 9. Client A sends an IOMP V2 Membership Report (Destination IP Address=239.216.63.248, Group Address239.216.63.248);
  • 10. Access Switch/Router #1 forwards IGMP V2 Membership Report to backbone (assuming it has no other interfaces in Group Address=239.216.63.248);
  • 11. Gateway Router does not forward “Administratively Scoped” membership report to the Internet;
  • 12.IPMS120 receives IGNIP V2 Membership Report and transmits 239.216.63.248 multicast outNIC#2 onto Filtered Stream—the data payload of the 239.216.63.248 multicast includes the IPMS120 P Address, and a test pattern;
  • 13. Access Switch/Router #1 forwards 239.216.63.248 multicast to Client A only;
  • 14. Gateway Router ignores 239.216.63.248 multicast since it is an Administratively scoped address;
  • 15. Client A receivesIPMS120 IP Address and test pattern and then sends an IGMP Leave Group (Destination IP Address=224.0.0.2, Group Address=239.216.63.248);
  • 16. Access Switch/Router #1 verifies it has no other interfaces in Group Address=239.216.63.248 (using IGMP Query), forwards IGMP Leave Group to backbone, and immediately stops forwarding the 239.216.63.248 multicast to Client A;
  • 17. Gateway Router ignores IGMP Leave Group command since it is on an administratively scoped address;
  • 18.IPMS120 receives IGMP Leave Group, verifies it has no other Clients in Group Address=239.216.63.248 (using IGMP Query), and immediately stops transmission of the 239.216.63.248 multicast;
  • 19. Client A sends a UDP packet (Destination IP Address=28.0.0.255, Port=255) to theIPMS120;
  • 20. Access Switch/Router #1 forwards UDP packet to backbone;
  • 21. Gateway Router does not forward packet to Internet since it is destined for a local administratively scoped address;
  • 22.IPMS120 receives UDP packet and sends UDP packet (Destination IP Address=128.0.0.1, Port=255);
  • 23. Gateway Router does not forward packet to Internet since it is destined for a local administratively scoped address;
  • 24. Access Switch/Router #1 forwards UDP packet to Client A;
  • 25. Client A receives UDP packet.

The following operations occur when Client A joins Multicast Group 239.216.0.8:

• • 26. Client A sends an IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8);
  • 27. Access Switch/Router #1 forwards IGMP V2 Membership Report to the LAN backbone(assuming it has no other interfaces in Group Address=239.216.63.248).
  • 28. Gateway Router ignores IGMP V2 Membership Report since it is an administratively scoped address;
  • 29.IPMS120 receives IGMP V2 Membership Report and transmits 239.216.0.8 multicast out NIC2 onto Filtered Stream;
  • 30. Access Switch/Router #1 forwards 239.216.0.8 multicast to Client A only;
  • 31. Gateway Router ignores 239.216.0.8 multicast (“Administratively Scoped” address);
  • 32. Client A receives 239.216.0.8 multicast.

The following query operations ensure that theIPMS120 does not transmit a Multicast Group that a client has silent left:

• • 33. Access Switch/Router #1 sends IGMP Group-Specific Query (Destination IP Address=239.216.0.8, Group Address=239.216.0.8) to Client A
  • 34. If Access Switch/Router #1 receives an IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8), do nothing;
  • 35. If there is no Membership Report then Access Switch/Router #1 sends IGMP Leave Group(Destination IP Address=224.0.0.2, Group Address=2239.216.0.8) to backbone and immediately stops forwarding the 239.216.0.8) multicast to all Clients (including Client A): operations then proceed at Step 40;
  • 36.IPMS120 sends UDP packet(Destination IP Address=239.216.63.240, Port=255);
  • 37. Client A receives UDP packet and responds with UDP packet (Destination IP Address=239.216.63.240. Port=255) (other Clients will receive and ignore this packet);
  • 38. IfIPMS120 receives no UDP response, then it immediately stops forwarding the 239.216.0.8 to all Clients (group left due to no response).

The following operations occur when Client A purposely leaves the Group;

• • 39. Client A sends an IGMP Leave Group (Destination IP Address=224.0.0.2, Group Address=239.216.0.8);
  • 40. Access Switch/Router #1 receives IGMP Leave Group, verifies it has no other interfaces in Group Address=239.216.0.8 (using IGMP Query), forwards IOMP Leave Group command to the LAN backbone, and immediately stops forwarding the 239.216.0.8 multicast to Client A;
  • 41. Gateway Router ignores the IGMP Leave Group command since it is directed on an administratively scoped address;
  • 42.IPMS120 receives the IGMP Leave Group command, verifies it has no other Clients in Group Address=239.216.0.8 (using IGMP Query), and immediately stops transmission of 239.216.0.8 multicast.

The following handshake operations occur during final termination:

• • 43. Client A sends a UDP packet (Destination IP Address=128.0.0.255, Port=255) to theIPMS120
  • 44. Access Switch/Router #1 forwards UDP packet to backbone;
  • 45. Gateway Router ignores the message since it is routed locally;
  • 46.IPMS120 receives the IDP packet and sends a UDP packet (Destination IP Address=128.0.0.1, Port=255) to Client A;
  • 47. Gateway Router ignores message routed locally;
  • 48. Access Switch/Router #1 forwards the UDP packet to Client A;
  • 49. Client A receives UDP packet.

ISP Model5—ISP with Multiple LAN Segments/Multicast Streams Segmented—Scenario2

In the example ofFIG. 25. Client A and theIPMS120 first join Multicast Group 239.216.63.240 to establish a mechanism for sending multicast control messages to each other. Next, Client A joins, receives, and leaves Multicast Group 239.216.63.248 to receive a brief multicast from theIPMS120. After that, Client A joins and receives Multicast Group 239.216.0.8. Then, network elements query the group so that multicast traffic can be pruned in the event group members silently leave the group. Finally, Client A leaves Multicast Group 239216.0.8.

TheIPMS120 filters the multicast streams sent to each segment so that only multicast addresses which are currently “joined” will be sent to the LAN Switch per segment. This implies that the LAN switch does not have to support IGMP V2, although this provision is not mandatory.

In the scenario ofFIG. 25, the following assumptions have been made:

• • IPMS120 IP Address=128.0.0.255, Client A IP Address=128.0.0.1;
  • All IP Multicast Addresses transmitted by theIPMS120 are “Administratively Scoped” addresses in the range 239.216.0.0 through 239.219.255.255 (addresses 239.216.0.8, 239.216.63.240, 239.216.63.248 used in this example);
  • Access Switch/Routers andIPMS120 support IGMP V2;
  • LAN Switch may or may not support IGMP V2;
  • LAN Switch configuration:
    • Virtual LAN#1=LAN Segment #1, Backbone,IPMS120 Control, FilteredStream#1;
    • Virtual LAN#2=LAN Segment #2. Backbone,IPMS120 Control, FilteredStream#2
  • Remote Router does not forward IGMP messages with “Administratively Scoped” Multicast addresses (this includes messages with Dest IP=239.*.*.*, and IGMP messages with Dest IP=224.0.0.1/224.0.0.2 that specify a Group Address=239.*.*.*);
  • TheIPMS120 and the Clients use Multicast Address=239.216.63.240 to pass proprietary UDP packets using UDP Port=255.

The following operations occur during initial handshake in the system:

• • 1.IPMS120 sends an IOMP V2 Membership Report (Destination IP Address=239.216.63.240, Group Address=239.216.63.240);
  • 2. LAN Switch receives IOMP V2 Membership Report, forwards the message, and adds theIPMS120 to the Groups the 239.216.63.240 multicast being used for multicast control messages;
  • 3. Gateway Router does not forward the administratively scoped membership report to the Internet;
  • 4. Client A sends an IGMP V2 Membership Report (Destination IP Address=239.216.63.240, Group Address=239.216.63.240);
  • 5. Access Switch/Router #1 forwards IGMP V2 Membership Report to LAN Segment #1 (assuming it has no other interfaces in Group Address=239.216.63.240);
  • 6. LAN Switch receives IGMP V2 Membership Report, forwards the message, and adds Client A to the Group;
  • 7. Gateway Router does not forward the administratively scoped membership report to the Internet;
  • 8.IPMS120 receives IGMP V2 Membership Report, the 239.216.63.240 multicast being used for multicast control messages;
  • 9. Client A sends an IGMP V2 Membership Report (Destination IP Address=239.216.63.248, Group Address=239.216.63.248);
  • 10. Access Switch/Router #1 forwards IGMP V2 Membership Report to LAN Segment #1 (assuming it has no other interfaces in Group Address=239.216.63.248);
  • 11. LAN Switch receives IGMP V2 Membership Report and forwards the message;
  • 12. Gateway Router does not forward the administratively scoped membership report to the Internet;
  • 13.IPMS120 receives IGMP V2 Membership Report and transmits 239.216.63.248 multicast outNIC#2 andNIC#3 onto FilteredStreams1 and2—the data payload of the 239.216.63.248 multicast includes theIPMS120 IP Address, and a test pattern;
  • 14. If LAN Switch is IGMP V2 enabled, it will forward 239.216.63.248 multicast toLAN Segment #1 only. If it isn't, then the 239.216.63.248 multicast will be forwarded to bothLAN Segment #1 andLAN Segment #2;
  • 15. Access Switch/Router #1 forwards 239.216.63.248 multicast to Client A only;
  • 16. Client A receivesIPMS120 IP Address and test pattern and then sends an IGMP Leave Group (Destination IP Address=224.0.0.2 Group Address=239.216.63.248);
  • 17. Access Switch/Router #1 receives IGMP Leave Group, verifies it has no other interfaces in Group Address239.216.63.248 (using IGMP Query), forwards IGMP Leave Group toLAN Segment #1, and immediately stops forwarding the 239.216.63.248 multicast to Client A;
  • 18. LAN Switch receives the IGMP Leave Group and forwards the message. If it is IGMP V2 enabled, it will verify it has no otherLAN Segment #1 Clients in Group Address=239.216.63.248 (using IGMP Query), and immediately stop transmission of 239.216.63.248 multicast toLAN Segment #1;
  • 19. Gateway Router ignores IOMP Leave Group since it is on an administratively scoped address;
  • 20.IPMS120 receives IGMP Leave Group, verifies it has no other Clients in Group Address=239.216.63.248, and immediately stops transmission of the 239.216.63.248 multicast;
  • 32.IPMS120 receives IGMP V2 Membership Report and transmits 239.216.0.8 multicast outNIC#2 onto FilteredStream #1;
  • 33. LAN Switch forwards 239.216.0.8 multicast toLAN Segment #1 only;
  • 34. Access Switch/Router #1 forwards 239.216.0.8 multicast to Client A only;
  • 35. Client A receives 239.216.0.8 multicast.

The following query operations occur to ensure that the IPMS does not unnecessarily provide a Group multicast transmission when there are no subscribers:

• • 36. Access Switch/Router #1 sends IGMP Group-Specific Query (Destination IP Address=239.216.0.8, Group Address=239.216.0.8) to Client A;
  • 37. If Access Switch/Router #1 receives an IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address 239.216.0.8), do nothing;
  • 38. If there is no Membership Report, then Access Switch/Router #1 sends IGMP Leave Group (Destination IP Address=224.0.0.2, Group Address=239.216.0.8) toLAN Segment #1 and immediately stops forwarding the 239.216.0.8 multicast to all clients (including Client A), operations then proceed from Step 53;
  • 39.IPMS120 sends UDP packet(Destination IP Address=239.216.63.240, Port=255) fromNIC #1;
  • 40. If LAN Switch is IGMP V2 enabled, it will forward the packet to all interfaces currently monitoring the 239.216.63.240 stream. If it is not IGMP V2 enabled, the packet will be forwarded to all LAN interfaces.
  • 41. Gateway Router will ignore the administratively scoped packet;
  • 42. Access Switch/Routers will forward the packet to all Clients listening to the 239.216.63.240 stream;
  • 43. Client A will respond with a UDP packet (Destination IP Address=239.216.63.240, Port=255);
  • 44. The packet will be forwarded by Access/Switch Router #1 toLAN Segment #1;
  • 45. The LAN Switch will forward the packet to theIPMS120NIC #1;
  • 46. Gateway Router will ignore the administratively scoped packet;
  • 47. IfIPMS120 receives no UDP response, then it immediately stops forwarding the 239.216.0.8 to all Clients (group is left due to no response); Independently, if the LAN Switch is IGMP V2 enabled, the following operations occur:
  • 48. LAN Switch sends IGMP Group-Specific Query (Destination IP Address=239.216.0.8, Group Address=239.216.0.8) toLAN Segment #1;
  • 49. If LAN Switch receives IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8), do nothing
  • 50. If there is no Membership Report then LAN Switch sends IGMP Leave Group (Destination IP Address=224.0.0.2, Group Address=239.216.0.8) toIPMS120 and immediately stops transmission of 239.216.0.8 multicast to LAN Segment #1 (group is left due to no response);

The following operations occur when Client A leaves Group Address 239.216.0.8:

• • 51. Client A sends an IGMP Leave Group(Destination IP Address=224.0.0.2, Group Address=239.216.0.8):
  • 52. Access Switch/Router #1 receives IGMP Leave Group, verifies it has no other interfaces in Group Address=239.216.0.8 (using IGMP Query), forwards IGMP Leave Group toLAN Segment #1, and immediately stops forwarding the 239.216.0.8 multicast to Client A;
  • 53. LAN Switch receives IGMP Leave Group and forwards the message. If it is IGMP V2 enabled it verifies it has no otherLAN Segment #1 Clients in Group address 239.216.0.8 (using IGMP Query), and immediately stops transmission of 239.216.0.8 multicast to LAN Segment 1:
  • 54. Gateway Router ignores IGMP Leave Group since it is in an administratively scoped address packet;
  • 55.IPMS120 receives IGMP Leave Group, verifies it has no other Clients in Group Address=239.216.0.8, and immediately stops transmission of 239.216.0.8 multicast.

The following termination handshake operations occur upon termination of the multicast subscription:

• • 56. Client A sends a UDP packet (Destination IP Address=128.0.0.255, Port=255) to the IPMS120:
  • 57. Access Switch/Router #1 forwards UDP packet to LAN Segment #1:
  • 58. LAN Switch forwards packet toIPMS120NIC #1;
  • 59.IPMS120 receives UDP packet and sends a UDP packet (Destination IP Address=28.0.0.1, Port255) to Client A;
  • 60. LAN Switch forwards packet toLAN Segment #1;
  • 61. Gateway Router will ignore the administratively scoped packet;
  • 62. Access Switch/Router #1 forwards packet to Clients A;
  • 63. Client A receives UDP packet.

ISP Model6—Large ISP with Affiliated ISP—Scenario2

In the example ofFIG. 26, Remote Client H and theIPMS120 first join Multicast Group 239.216.63.240 to establish a mechanism for sending multicast control messages to each other. Next, Remote Client H joins receives, and leaves Multicast Address 239.216.63.248 to receive a brief multicast from theIPMS120. After that, Client H joins and receives Multicast Group 239.216.0.8. Then, network elements query the group so that multicast traffic can be pruned in the event group members silently leave the group. Finally, Client H leaves Multicast Group 239.216.0.8.

TheIPMS120 filters the multicast streams sent to each segment so that only multicast addresses that are currently “joined” will be sent to the LAN Switch per segment. This implies that the LAN switch does not have to support IGMP V2, although this is not necessary. The LAN Switch may filter the multicast stream sent to each segment so that only multicast addresses which are currently “joined” by plans on a segment will be placed on the segment. For the Remote ISP the multicast streams preferably to not use bandwidth on the Router link to the ISP (to avoid impacting normal Internet traffic). Rather, a bridged connection is used to send the streams to the Remote ISP. The only segments that receive the multicast streams areLAN Segment #1 and the bridged connection to the Remote ISP that is considered to beLAN Segment #2.

In this scenario, the following assumptions have been made:

• • IPMS120 IP Address 28.0.0.255, Client A IP Address=128.0.0.1;
  • All IP Multicast Addresses transmitted by theIPMS120 are “Administratively Scoped” addresses in the range 239.216.0.0 through 239.219.255.255 (addresses 239.216.0.8, 239.216.63.240, 239.216.63.248 used in this example);
  • Access Switch/Router andIPMS120 support IGMP V2;
  • LAN Switch may or may not support IGMP V2;
  • LAN Switch configuration:
    • Virtual LAN#1LAN Segment #1 Backbone,IPMS120 Control, FilteredStream#1;
    • Virtual LAN#2=LAN Segment #2,IPMS120 Control, FilteredStream#2;
    • Virtual LAN#3LAN Segment #3,Backbone;
  • LAN Bridge configuration: Only forward 239.216.0.0-239.219.255.255; 224.0.0.1, 224.0.0.2;
  • Remote Router does not forward IGMP messages with “Administratively Scoped” Multicast addresses (this includes messages with Dest IP239.*.*.*, and IGMP messages with Dest IP=224.0.0.1/224.0.0.2 that specify a Group Address=239.*.*.*);
  • TheIPMS120 and the Clients use Multicast Address=239.216.63.240 to pass UDP packets using UDP Port=255.

In this scenario, the followings initial handshake operations take place:

• • 1.IPMS120 sends an IGMP V2 Membership Report (Destination IP Address=39.216.63.240. Group Address=239.216.63.240);
  • 2. LAN Switch receives IGMP V2 Membership Report, forwards the messages and adds theIPMS120 to the Group, the 239.216.63.240 multicast being used for multicast control messages;
  • 3. Gateway Router does not forward the administratively scoped membership report to the Internet;
  • 4. Client H sends an IGMP V2 Membership Report (Destination IP Address=239.216.63.240, Group Address=239.216.63.240);
  • 5. Access Switch/Router #1 forwards IGMP V2 Membership Report to LAN Segment#1 (assuming it has no other interfaces in Group Address=239.216.63.240);
  • 6. LAN Switch receives IGMP V2 Membership Report, forwards the message, and adds Client H to the Group;
  • 7. Gateway Router does not forward the administratively scoped membership report to the Internet;
  • 8.IPMS120 receives IGMP V2 Membership Report the 239.216.63.240 multicast being used for multicast control messages;
  • 9. Client H sends an IGMP V2 Membership Report (Destination IP Address=239.216.63.248, Group Address=239.216.63.248);
  • 10. Access Switch/Router #2 forwards IGMP V2 Membership Report to Remote Backbone (assuming it has no other interfaces in Group Address=239.216.63.248);
  • 11. LAN Bridge forwards IGMP V2 Membership Report;
  • 12. Remote Router ignores the administratively scoped IGMP V2 Membership Report;
  • 13. LAN Switch receives IGMP V2 Membership Report, forwards the message, and enables transmission of 239.216.63.248 multicast toLAN Segment #2;
  • 14.IPMS120 receives IGMP V2 Membership Report and transmits 239.216.63;248 multicast outNIC#2 andNIC#3 onto FilteredStreams1 and2—the data payload of the 239.216.63.248 multicast includes theIRMS120 IP Address, and a test pattern;
  • 15. If LAN Switch is IGMP V2 enabled, it will forward 239.216.63.248 multicast toLAN Segment #2 only. If it is not so enabled, then the 239.216.63.248 multicast data will be forwarded to bothLAN Segment #1 andLAN Segment #2;
  • 16. LAN Bridge forwards the 239.216.63.248 multicast data;
  • 17. Access Switch/Router #2 forwards 239.216.63.248 multicast to Client H only;
  • 18. Remote Router ignores 239.216.63.248 multicast data;
  • 19. Client H receives theIPMS120 IP Address and test pattern and then sends an IGMP Leave Group (Destination IP Address=224.0.0.2. Group address=239.216.63.248);
  • 20. Access Switch/Router 2 receives IGMP Leave Group, verifies it has no other interfaces in Group Address=239.216.248 (using IGMP Query), forwards IGMP Leave Group to LAN Bridge, and immediately stops forwarding the 239.216.63.248 multicast to Client H;
  • 21. LAN Bridge forwards the IGMP Leave Group command;
  • 22. Remote Router ignores the administratively scoped IGMP Leave Group command;
  • 23. LAN Switch receives IGMP Leave Group and forwards the message. If it is IGMP V2 enabled, it will verify it has no otherLAN Segment #2 Clients in Group address=239.216.63.248 (using IGMP Query), and will immediately stop transmission of the 239.216.63.248 multicast toLAN Segment #2;
  • 24.IPMS120 receives the IGMP Leave Group command, verifies it has no other Clients in Group Address=239.216.63.248, and immediately stops transmission of the 239.216.63.248 multicast data;
  • 25. Client H sends a UDP packet (Destination IP Adress=128.0.0.255, Port=255) to theIPMS120;
  • 26. Access Switch/Router #2 forwards a UDP packet to the backbone of the remote ISP;
  • 27. LAN Bridge forwards the IGMP V2 Membership Report;
  • 28. Remote Router ignores the administratively scoped IGMP V2 Membership Report;
  • 29. LAN Switch forwards the UDP packet to theIPMS120 control stream (NIC #1);
  • 30.IPMS120 receives UDP packet and sends UDP packet response (Destination IP Address=128.0.0.1, Port=255) fromNIC #1;
  • 31. LAN Switch forwards the UDP packet to theLAN Segment #2 since the packet is addressed to Client H;
  • 32. Access Switch/Router #2 forwards UDP packet to Client H;
  • 33. Client H receives UDP packet.

The following operations occur when Client H joins Multicast Group 239.216.0.8;

• • 34. Client H sends an IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.08);
  • 35. Access Switch/Router #2 forwards IGMP V2 Membership Report to Remote Backbone (assuming it has no other interfaces in Group Address=239.216.0.8);
  • 36. LAN Bridge forwards IGMP V2 Membership Report;
  • 37. Remote Router ignores the administratively scoped IGMP V2 Membership Report;
  • 38. LAN Switch receives IGMP V2 Membership Report and forwards the message. If it is IGMP V2 enabled, it will enable transmission of 239.216.0.8 multicast toLAN segment #2;
  • 39.IPMS120 receives the IGMP V2 Membership Report and transmits the 239.216.0.8 multicast throughNIC #3 onto FilteredStream #2;
  • 40. LAN Switch forwards 239.216.0.8 multicast toLAN Segment #2 only;
  • 41. LAN Bridge forwards the 239.216.0.8 multicast data;
  • 42. Access Switch/Router #2 forwards 239.216.0.8 multicast data to Client H only;
  • 43. Remote Router ignores 239.216.0.8 multicast data;
  • 44. Client H receives 239.216.0.8 multicast.

The following query operations also take place to ensure that unnecessary multicast data is not transmitted over any LAN:

• • 45. Access Switch/Router #2 sends IGMP Group-Specific Query (Destination IP Address=239.216.0.8, Group Address=239.216.0.8) to Client H;
  • 46. If Access Switch/Router #2 receives an IGMP V2 Membership Report (Destination IP Address=39.216.0.8, Group Address=239.216.0.8), do nothing:
  • 47. If there is no Membership Report, then Access Switch/Router #2 sends an IOMP Leave Group command (Destination IP Address=224.0.0.2, Group Address=39.216.0.8) to the backbone of the remote ISP and immediately stops forwarding the 239.216.0.8 multicast data to Client H; operations then proceed from Step 63 below;
  • 48.IPMS120 sends UDP packet (Destination IP Address=239.216.63.240, Port=255) fromNIC #1;
  • 49. If LAN Switch is IGMP V2 enabled, it will forward the packet to all interfaces currently monitoring the 239.216.63.240 stream if it is not IGMP V2 enabled, the packet will be forwarded to all LAN interfaces
  • 50. Access Switch/Routers forwards the packet to all Clients listening to the 239.216.63.240 stream;
  • 51. Client H responds with a UDP packet (Destination IP Address=239.216.63.240, Port=255);
  • 52. Access/Switch Router #2 forwards the packet to the backbone of the remote ISP;
  • 53. LAN Bridge forwards packet;
  • 54. Remote Router ignores packet;
  • 55. The LAN Switch forwards packet to theIPMS120NIC #1;
  • 56. IfIPMS120 does not receive a UDP response, then it immediately stops forwarding the 239.216.0.8 to all Clients (group is left due to no response). If the LAN Switch is IGMP V2 enabled, the following operations will take place;
  • 57. LAN Switch sends IGMP Group-Specific Query (Destination IP Address=239.216.0.8, Group Address=239.216.0.8) toLAN Segment #2;
  • 58. LAN Bridge forwards IGMP Group-Specific Query;
  • 59. If LAN Switch receives an IGMP V2 Membership Report (Destination IP Address=239.216.0.8, Group Address=239.216.0.8), then do nothing;
  • 60. If there is no Membership Report, then IAN Switch immediately stops transmission of 239.216.0.8 multicast to LAN Segment #2 (group is left due to no response).

The following operations take place when Client H leaves Multicast Group 239.216.0.8:

• • 61. Client H sends an IGMP Leave Group command (Destination IP Address=224.0.0.2, Group Address=239.216.0.8);
  • 62. Access Switch/Router #2 receives the IGMP Leave Group command. verifies it has no other interfaces in Group Address=239.216.0.8 (using IGMP Query), forwards the IGMP Leave Group to the backbone of the remote ISP, and immediately stops forwarding the 239.216.0.8 multicast data to Client H;
  • 63. LAN Bridge forwards IGMP Leave Group command;
  • 64. Remote Router ignores the administratively scoped IGMP Leave Group command;
  • 65. LAN Switch receives the IGMP Leave Group command and forwards the message: if it is IGMP V2 enabled, it verifies it has no otherLAN Segment #2 Clients in Group Address=239.216.0.8 (using IGMP Query), and immediately stops transmission of 239.216.0.8 multicast toLAN Segment #2;
  • 66.IPMS120 receives the IGMP Leave Group command, verifies it has no other Clients in Group Address=239.216.0.8, and immediately stops transmission of the 39.216.0.8 multicast.

The following termination handshake operations also take place:

• • 67. Client H sends a UDP packet (Destination IP Address=128.0.0.255. Port=255) to theIPMS120;
  • 68. Access Switch/Router #2 forwards the LTDP packet to the backbone of the remote ISP;
  • 69. LAN Bridge forwards the packet;
  • 70. Remote Router ignores the packet;
  • 71. LAN Switch forwards the packet toIPMS120NIC #1;
  • 72.IPMS120 receives the UDP packet and sends a UDP packet (Destination IP Address=128.0.0.1, Port=255) to Client H;
  • 73. LAN Switch forwards the packet toLAN Segment #2 only;
  • 74. LAN Bridge forwards the packet;
  • 75. Access Switch/Router #2 forwards the packet to Client H only; and
  • 76. Client H receives the UDP packet.

If remote clients join “normal” multicast groups through the remote router, the 224.0.0.1 and 224.0.0.2 IGMP V2 messages will be bridged to the LAN Switch. The LAN Switch will forward the IGMP messages throughLAN segment #2 to theIPMS120. TheIPMS120 will ignore the messages issued for a non-existent stream.

FIG. 27 shows a basic ISP configuration. The Internet is connected to an internal 10 BaseT LAN. This internal LAN has a local file server that is used for locally served Web pages. Also on this LAN is connected a remote access server (modem pool) which is used to Connect the ISP customers via the LEC (local exchange carrier—the local phone company) to the Internet.

FIG. 28 shows how this ISPO grows to serve more customers. Alayer3 switch is added to the Internal ISP LAN. This LAN is usually interconnected by 100 BaseT added to the internal ISP LAN. This LAN is usually interconnected by 100 BaseT or FDDI transmission technology. The switch is used to interconnect multiple 10 BaseT LAN segments to the ISP LAN. Each of these segments have multiple remote access servers that are used to connect users to the Internet.

FIG. 29 shows how broadband multimedia data is inserted into an ISP using the ideas described in this application. This configuration takes advantage of current ISP architectures. Many ISP's today have evolved over time as shown inFIG. 27 andFIG. 28. They started with one remote access router serving a few customers (FIG. 27) and have expanded to multiple remote access routers (FIG. 28).FIG. 29 shows the addition of multiple satellite receivers that receive multicast data.

In this configuration, theLayer 3 IP switch performs several functions. The first function is to connect the proper multicast stream form the appropriate satellite receiver to the appropriate LAN segments. This requires the switch to implement the IP Multicast Protocol (RFC1112).

The second function is to connect the proper Internet traffic to the appropriate LAN segment.

The third function of theLayer 3 switch is to perform the IOMP querier function as specified in RFC1112.

If the existingLayer 3 switch meets the above requirements, then it can be used. If not, then the ISP must upgrade the switch with one that meets these requirements. The commercially available HP800T switch is one example of such alayer3 multicast enabled switch.

Such a configuration has the advantage of simplicity since the satellite receiver only needs to strip the HDLC (or other) encapsulation from the incoming data and electrically convert the data to the ethernet format. It does not need to have any knowledge of IP multicasting protocols.

Enhancements that could be incorporated in the receiver could be multicast address translation and data de-scrambling. In this case, the receiver must understand the IP multicasting protocol to perform these appropriate functions.

FIG. 30 illustrates the layout of an exemplarytraditional web page800 suitable for use in the present multicast system. As illustrated, theweb page800 includes avideo display window800 that accepts and displays a video data stream from the broadcast transmission. External to thevideo display window800, text, and graphic content relating to the content of the video is displayed. Such content can be provided in the broadcast transmission itself, over the backbone of the Internet, or from storage at the ISP.

Theweb page800 is also provided with a plurality of baudrate selection buttons810,815,820, and825. Each button corresponds to a baud rate of a broadcast video stream, each stream having the same multimedia content. For example,button810 may correspond to transmission of the media content for thedisplay window800 at 14.4K. Similarly,buttons815,820, and825 may correspond to baud rates of 28.8 K. 56.6 K. and 1.5 MB, respectively. This allows the client to select a baud rate for the video transmission rate that is suited to his system.

The web page provides substantial information and versatility to the user. The user may be presented with a substantially continuous flow of video information while concurrently having text and other information presented to him that may or may not be related to the video to allow the user to select other web pages, audio information, further video content, etc. These further selections may relate to the particular topic. product, etc., provided in the video content. The user may be given an option to select multiple video channels that may be supplied concurrently. The user is provided with a substantial number of channels to choose from, thereby allowing the user to select the desired video content.

The web pace needed not necessarily be provided with buttons for the selection of baud rate. Rather, a software plug-in for the web browser used by the client may be used to automatically join the appropriate multicast group depending on the data rate at which the client communicates with the ISP. In such instances, the plug-in software first detects the data rate at which the client is communicating with the Internet service provider. When a client wishes to view a particular video stream content, the software compares this detected data rate against a table of different data rates for the same content, each data rate corresponding to a unique multicast Group address. The software joins the client to the multicast group having the maximum data rate that does not exceed the data rate at which the software detected the communications between the client and the Internet service provider.

An exemplary embodiment of software that may be used for this purpose is set forth in an “Appendix A”, filed with related application Ser. No. 08/969,164, now U.S. Pat. No. 6,101,180, the entire contents of which is incorporated by reference herein. Appendix A includes listings of software source code in C++ for automatically detecting the baud rate at which the client is connected to the system and selecting the proper multicast join group.

Numerous modifications can be made to the foregoing system without departing from the spirit and scope of the various inventive aspects of this invention as set forth in the appended claims Therefore, it is the intention of the inventors to encompass all such chances and modifications that fall within the scope of the appended claims.

Claims (46)

1. A method of transmitting digital content to a plurality of separate users accessing Internet services at least in part via conventional two-way Internet protocol (IP) connection, said digital content comprising digital data and/or digital audio and/or digital video, the method comprising the steps of:

a) formatting said digital content in accordance with an IP protocol to generate IP digital data;

b) providing a streaming transmission of the IP digital data from a transmission site to a remote Internet point of presence of an Internet service provider (ISP) through one or more substantially one-way data flow bandwidth portions of a digital communications medium that is substantially unaffected by conventional two-way IP Internet communications traffic;

c) multicastiag multicasting the IP digital data transmitted by step (b) from the remote Internet point of presence to a plurality of separate receiving Internet user apparatus connected to but distant from the remote Internet point of presence; and

d) contemporaneously with step c), transmitting relatively time-insensitive additional IP digital data via a conventional two-way IP connection that is separate from the one-way data flow bandwidth portions to the remote Internet point of presence and then to the plurality of separate receiving Internet user apparatus;

wherein, on each among the plurality of separate receiving Internet user apparatus, received IP digital data multicast by step (c) and received additional IP digital data transmitted by step (d) is processed to allow simultaneous use of both.

2. A method of providing digital content to a plurality of disparate users accessing Internet services at least in part via conventional two-way Internet protocol (IP) connection, said digital content comprising digital data and/or digital audio and/or digital video, the method comprising the steps of:

a) formatting said digital content in accordance with an IP protocol to produce IP digital data;

b) providing a streaming transmission of the IP digital data from a transmission site to a distant routing station at an internet service provider's internet point of presence through one or more substantially one-way data flow bandwidth portions of a digital communications medium that is substantially unaffected by conventional two-way IP Internet communications traffic; and

c) providing, from the Internet service provider's Internet point of presence, multicast access of said IP digital data received via streaming transmission at the Internet service provider's Internet point of presence by step (b) to said plurality of disparate users accessing Internet services via two-way IP connection.

3. The method ofclaim 2 wherein one or more of said substantially one-way data flow bandwidth portions comprise one or more video content channels.

4. The method ofclaim 2 wherein one or more of the substantially one-way data flow bandwidth portions comprise one or more audio content channels.

5. The method ofclaim 2 further including the step of receiving and processing at least one IP request from at least one of said separate users

6. The method ofclaim 2 wherein the multicast access service provided in step c) is localized to a predetermined geographic region.

7. The method ofclaim 2 wherein the digital communications medium substantially unaffected by conventional two-way IP Internet communications traffic comprises, at least in part, an extraterrestrial satellite communications system.

8. The method ofclaim 2 wherein the digital communications medium substantially unaffected by conventional two-way IP Internet communications traffic is a substantially terrestrial communications system.

9. The method ofclaim 2 wherein the digital communications medium substantially unaffected by conventional two-way IP Internet communications traffic is a reserved portion of a commercial IP communications network.

10. A method of providing digital streaming content to a plurality of disparate users accessing Internet services at least in part via conventional two-way Internet protocol (IP) connections, the streaming digital content comprising digital data and/or digital audio and/or digital video, the method comprising the steps of:

a) transmitting the digital streaming content from a transmission site to a distant routing station at an Internet service provider's Internet point of presence through one or more substantially one-way data flow bandwidth portions of a digital communications medium that is substantially unaffected by conventional two-way IP Internet communications traffic; and

b) providing, from the Internet service provider's Internet point of presence, access to the digital streaming content received at the Internet service provider's Internet point of presence via step (a), by multicast transmission to said plurality of disparate users accessing Internet services via two-way IP connection.

11. A method of providing access to multicast digital content to a plurality of disparate users accessing Internet services at least in part via two-way Internet protocol (IP) connections, the digital content comprising digital data and/or digital audio and/or digital video information, the method comprising the steps of:

a) transmitting the digital data from a transmission site to a distant routing station at an Internet service provider's Internet point of presence through one or more substantially one-way data flow bandwidth portions of a digital communications data transport service or transmission medium that effectively bypasses congested portions of the Internet and remains substantially unaffected by IP Internet communications traffic;

b) receiving the digital data, transmitted by step (a), at said routing station; and

c) providing access to the digital data by multicast transmission delivery from said Internet point of presence to said plurality of disparate users accessing Internet services via two-way IP connection.

12. A method of transmitting digital data, said digital data comprising streaming and/or non-streaming data encompassing both video and audio information content, to a plurality of disparate Internet users accessing Internet services at least in part via conventional two-way Internet protocol (IP) connection, the method comprising the steps of:

a) transmitting the digital data to at least one distant Internet point of presence of an Internet service provider through one or more substantially one-way data flow bandwidth portions of a digital communications medium that is disparate from and substantially unaffected by conventional two-way IP Internet communications traffic; and

b) multicast transmitting the digital data from said at least one distant Internet point of presence to said plurality of disparate Internet users over a two-way IP network connecting said at least one Internet point of presence to said disparate Internet users, wherein at least one or more of said plurality of disparate Internet users employ digital communications equipment that utilizes an Internet browser program or its equivalent to access Internet services.

13. The method ofclaim 12 wherein said digital communications equipment comprises a display device and said Internet browser program or its equivalent used by said plurality of disparate Internet users for accessing Internet services provides a screen display wherein at least a first portion of the display device screen is allocated for displaying the digital data received from said at least one distant Internet point of presence and wherein a separate portion of the display device screen is allocated for simultaneously conducting two-way interactive IP connectivity.

14. The method ofclaim 12 wherein one or more of said one-way data flow bandwidth portions comprise a one-way wireless transmission system.

15. The method ofclaim 12 wherein die transmitting of step a) comprises transmitting the digital data to plural Internet points of presence, including said at least one distant Internet point of presence, substantially through a reserved one-way data flow bandwidth portion.

16. The method ofclaim 12 wherein the two-way IP network comprises a telecommunications network.

17. The method ofclaim 12 wherein the two-way IP network comprises a cable network.

18. The method ofclaim 12 wherein the two-way IP network comprises a local area computer network.

19. The method ofclaim 16 wherein the telecommunications network includes a POTS line connecting communications equipment supporting said Internet browser program or its equivalent used by at least one of said plurality of disparate Internet users to said at least one distant Internet point of presence, wherein said line at browser may access and display said digital data transmitted via said one-way data flow bandwidth portions.

20. A method of providing localized multicast access to streaming digital content, said digital content comprising digital data and/or audio and/or video information, by a plurality of disparate Internet users accessing the Internet at least in part via conventional two-way Internet protocol (IP) connection, the method comprising the steps of:

providing a streaming transmission of digital content from a head-end content source through one or more substantially one-way data flow bandwidth portions of a communications medium that is disparate from and substantially unaffected by Internet communications traffic to at least one distant Internet point of presence of an Internet service access provider that provides IP digital data to one or more users via conventional two-way IP connections; and

distributing the streaming digital content via multicast transmission to said plurality of disparate Internet users that access and/or utilize the multicast streaming digital content received from the Internet service access provider via two-way IP connection.

21. The method ofclaim 20 wherein the distributing of streaming digital content via multicast transmission from to an Internet point of presence is localized to a predetermined geographic region.

22. A method of transmitting digital content at least in part via a two-way Internet protocol (IP) connection, said digital content comprising digital data and/or digital audio and/or digital video, the method comprising:

formatting said digital content in accordance with an IP protocol to generate IP digital data;

providing a streaming transmission of IP digital data through one or more substantially one-way data flow bandwidth portions of a digital communications medium that is substantially unaffected by two-way IP Internet communications traffic; and

transmitting relatively time-insensitive IP digital data via the two-way IP connection that is separate from the one-way data flow bandwidth portions,

wherein the IP digital data and the relatively time-insensitive IP digital data is transmitted to allow simultaneous use of both.

23. A method of providing digital content at least in part via a two-way Internet protocol (IP) connection, said digital content comprising digital data and/or digital audio and/or digital video, the method comprising:

receiving a streaming transmission of IP digital data through one or more substantially one-way data flow bandwidth portions of a digital communications medium that is disparate from and substantially unaffected by two-way IP Internet communications traffic, wherein the IP digital data is generated based on said digital content being formatted in accordance with an IP protocol; and

providing multicast access of said IP digital data received via streaming transmission via two-way IP connection.

24. The method of claim 23 wherein receiving the streaming transmission of the IP digital data includes receiving a streaming transmission of the IP digital data via one or more video content channels.

25. The method of claim 23 wherein receiving the streaming transmission of the IP digital data includes receiving a streaming transmission of the IP digital data via one or more audio content channels.

26. The method of claim 23 further comprising:

receiving at least one IP request; and

processing the at least one IP request.

27. The method of claim 23 further comprising providing a multicast access service that is localized to a predetermined geographic region.

28. The method of claim 23 wherein receiving the streaming transmission includes receiving the streaming transmission via a digital communications medium that comprises, at least in part, an extraterrestrial satellite communications system.

29. The method of claim 23 wherein receiving the streaming transmission includes receiving the streaming transmission via a digital communications medium that is a substantially terrestrial communications system.

30. The method of claim 23 wherein receiving the streaming transmission includes receiving the streaming transmission via a digital communications medium that is a reserved portion of a commercial IP communications network.

31. A method of providing digital streaming content at least in part via conventional two-way Internet protocol (IP) connections, the streaming digital content comprising digital data and/or digital audio and/or digital video, the method comprising:

receiving the digital streaming content through one or more substantially one-way data flow bandwidth portions of a digital communications medium that is disparate from and substantially unaffected by two-way IP Internet communications traffic; and

providing access to the digital streaming content by multicast transmission via two-way IP connection.

32. A method of providing access to multicast digital content at least in part via two-way Internet protocol (IP) connections, the digital content comprising digital data and/or digital audio and/or digital video information, the method comprising:

receiving the digital data from a transmission site at an Internet service provider's Internet point of presence through one or more substantially one-way data flow bandwidth portions of a digital communications data transport service or transmission medium that effectively bypasses congested portions of the Internet and remains substantially unaffected by IP Internet communications traffic; and

providing access to the digital data by multicast transmission delivery from said Internet point of presence via two-way IP connection.

33. A method of transmitting digital data, said digital data comprising streaming and/or non-streaming data encompassing both video and audio information content at least in part via conventional two-way Internet protocol (IP) connection, the method comprising:

receiving the digital data at at least one distant Internet point of presence of an Internet service provider through one or more substantially one-way data flow bandwidth portions of a digital communications medium that is disparate from and substantially unaffected by two-way IP Internet communications traffic; and

multicast transmitting the digital data from said at least one distant Internet point of presence.

34. The method of claim 33 wherein receiving the digital data includes receiving the digital data via a one-way wireless transmission system.

35. The method of claim 33 wherein receiving the digital data at least one distant Internet point of presence of an Internet service provider comprises receiving the digital data substantially through a reserved one-way data flow bandwidth portion.

36. The method of claim 33 wherein multicast transmitting the digital data includes multicast transmitting the digital data via a telecommunications network.

37. The method of claim 36 wherein multicast transmitting the digital data includes multicast transmitting the digital data via a POTS line connecting communications equipment supporting said Internet browser program or its equivalent, wherein said line at browser may access and display said digital data transmitted via said one-way data flow bandwidth portions.

38. The method of claim 33 wherein multicast transmitting the digital data includes multicast transmitting the digital data via a cable network.

39. The method of claim 33 wherein multicast transmitting the digital data includes multicast transmitting the digital data via a local area computer network.

40. A method of providing localized multicast access to streaming digital content, said digital content comprising digital data and/or audio and/or video information at least in part via two-way Internet protocol (IP) connection, the method comprising:

receiving a streaming transmission of digital content from a head-end content source through one or more substantially one-way data flow bandwidth portions of a communications medium that is disparate from and substantially unaffected by Internet communications traffic; and

distributing the streaming digital content via multicast transmission and/or utilize the multicast streaming digital content received via two-way IP connection.

41. The method of claim 40 wherein distributing streaming digital content via multicast transmission includes distributing the streaming digital content that is localized to a predetermined geographic region.

42. The method of 22 wherein providing the streaming transmission of IP digital data further comprising providing the streaming transmission of the IP digital data via one or more video content channels.

43. The method of 22 wherein providing the streaming transmission of IP digital data further comprising providing the streaming transmission of the IP digital data via one or more audio content channels.

44. The method of 22 wherein providing the streaming transmission of IP digital data further comprising providing the streaming transmission of the IP digital data via a digital communications medium that comprises, at least in part, an extraterrestrial satellite communications system.

45. The method of 22 wherein providing the streaming transmission of IP digital data further comprising providing the streaming transmission of the IP digital data via a digital communications medium that is a substantially terrestrial communications system.

46. The method of 22 wherein providing the streaming transmission of IP digital data further comprising providing the streaming transmission of the IP digital data via a digital communications medium that is a reserved portion of a commercial IP communications network.

Images