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Network Working Group:                                       M. McGovernRequest for Comments: 1707                              Sunspot GraphicsCategory: Informational                                       R. Ullmann                                           Lotus Development Corporation                                                            October 1994CATNIP: Common Architecture for the InternetStatus of this Memo   This memo provides information for the Internet community.  This memo   does not specify an Internet standard of any kind.  Distribution of   this memo is unlimited.Abstract   This document was submitted to the IETF IPng area in response toRFC1550  Publication of this document does not imply acceptance by the   IPng area of any ideas expressed within.  Comments should be   submitted to the big-internet@munnari.oz.au mailing list.Executive Summary   This paper describes a common architecture for the network layer   protocol. The Common Architecture for Next Generation Internet   Protocol (CATNIP) provides a compressed form of the existing network   layer protocols. Each compression is defined so that the resulting   network protocol data units are identical in format. The fixed part   of the compressed format is 16 bytes in length, and may often be the   only part transmitted on the subnetwork.   With some attention paid to details, it is possible for a transport   layer protocol (such as TCP) to operate properly with one end system   using one network layer (e.g. IP version 4) and the other using some   other network protocol, such as CLNP. Using the CATNIP definitions,   all the existing transport layer protocols used on connectionless   network services will operate over any existing network layer   protocol.   The CATNIP uses cache handles to provide both rapid identification of   the next hop in high performance routing as well as abbreviation of   the network header by permitting the addresses to be omitted when a   valid cache handle is available. The fixed part of the network layer   header carries the cache handles.McGovern & Ullmann                                              [Page 1]

RFC 1707                         CATNIP                     October 1994   The cache handles are either provided by feedback from the downstream   router in response to offered traffic, or explicitly provided as part   of the establishment of a circuit or flow through the network. When   used for flows, the handle is the locally significant flow   identifier.   When used for circuits, the handle is the layer 3 peer-to-peer   logical channel identifier, and permits a full implementation of   network-layer connection-oriented service if the routers along the   path provide sufficient features. At the same time, the packet format   of the connectionless service is retained, and hop by hop fully   addressed datagrams can be used at the same time. Any intermediate   model between the connection oriented and the connectionless service   can thus be provided over cooperating routers.CATNIP Objectives   The first objective of the CATNIP is a practical recognition of the   existing state of internetworking, and an understanding that any   approach must encompass the entire problem. While it is common in the   IP Internet to dismiss the ISO with various amusing phrases, it is   hardly realistic. As the Internet moves into the realm of providing   real commercial infrastructure, for telephone, cable television, and   the myriad other mundane uses, compliance with international   standards is an imperative.   The argument that the IETF need not (or should not) follow existing   ISO standards will not hold. The ISO is the legal standards   organization for the planet. Every other industry develops and   follows ISO standards. There is (no longer) anything special about   computer software or data networking.   ISO convergence is both necessary and sufficient to gain   international acceptance and deployment of IPng. Non-convergence will   effectively preclude deployment.   The CATNIP integrates CLNP, IP, and IPX. The CATNIP design provides   for any of the transport layer protocols in use, for example TP4,   CLTP, TCP, UDP, IPX and SPX to run over any of the network layer   protocol formats: CLNP, IP (version 4), IPX, and the CATNIP.Incremental Infrastructure Deployment   The best use of the CATNIP is to begin to build a common Internet   infrastructure. The routers and other components of the common system   are able to use a single consistent addressing method, and common   terms of reference for other aspects of the system.McGovern & Ullmann                                              [Page 2]

RFC 1707                         CATNIP                     October 1994   The CATNIP is designed to be incrementally deployable in the strong   sense: you can plop a CATNIP system down in place of any existing   network component and continue to operate normally with no   reconfiguration.  (Note: not "just a little". None at all. The number   of "little changes" suggested by some proposals, and the utterly   enormous amount of documentation, training, and administrative effort   then required, astounds the present authors.) The vendors do all of   the work.   There are also no external requirements; no "border routers", no   requirement that administrators apply specific restrictions to their   network designs, define special tables, or add things to the DNS.   When the end users and administrators fully understand the combined   system, they will want to operate differently, but in no case will   they be forced. Not even in small ways. Networks and end user   organizations operate under sufficient constraints on deployment of   systems anyway; they do not need a new network architecture adding to   the difficulty.   Typically deployment will occur as part of normal upgrade revisions   of software, and due to the "swamping" of the existing base as the   network grows. (When the Internet grows by a factor of 5, at least   80% will then be "new" systems.) The users of the network may then   take advantage of the new capabilities. Some of the performance   improvements will be automatic, others may require some   administrative understanding to get to the best performance level.   The CATNIP definitions provide stateless translation of network   datagrams to and from CATNIP and, by implication, directly between   the other network layer protocols. A CATNIP-capable system   implementing the full set of definitions can interoperate with any   existing protocol. Various subsets of the full capability may be   provided by some vendors.No Address Translation   Note that there is no "address translation" in the CATNIP   specification.  (While it may seem odd to state a negative objective,   this is worth saying as people seem to assume the opposite.) There   are no "mapping tables", no magic ways of digging translations out of   the DNS or X.500, no routers looking up translations or asking other   systems for them.   Addresses are modified with a simple algorithmic mapping, a mapping   that is no more than using specific prefixes for IP and IPX   addresses. Not a large set of prefixes; one prefix. The entire   existing IP version 4 network is mapped with one prefix and the IPX   global network with one other prefix. (The IP mapping does provideMcGovern & Ullmann                                              [Page 3]

RFC 1707                         CATNIP                     October 1994   for future assignment of other IANA/IPv4 domains that are disjoint   from the existing one.)   This means that there is no immediate effect on addresses embedded in   higher level protocols.   Higher level protocols not using the full form (those native to IP   and IPX) will eventually be extended to use the full addressing to   extend their usability over all of the network layers.No Legacy Systems   The CATNIP leaves no systems behind: with no reconfiguration, any   system presently capable of IP, CLNP, or IPX retains at least the   connectivity it has now.  With some administrative changes (such as   assigning IPX domain addresses to some CLNP hosts for example) on   other systems, unmodified systems may gain significant connectivity.   IPX systems with registered network numbers may gain the most.Limited Scope   The CATNIP defines a common network layer packet format and basic   architecture. It intentionally does not specify ES-IS methods,   routing, naming systems, autoconfiguration and other subjects not   part of the core Internet wide architecture. The related problems and   their (many) solutions are not within the scope of the specification   of the basic common network layer.Existing Addresses and Network Numbers   The Internet's version 4 numbering system has proven to be very   flexible, (mostly) expandable, and simple.  In short: it works.   However, there are two problems. Neither was considered serious when   the CATNIP was first developed in 1988 and 1989, but both are now of   major concern:   o The division into network, and then subnet, is insufficient.     Almost all sites need a network assignment large enough to     subnet. At the top of the hierarchy, there is a need to assign     administrative domains.   o As bit-packing is done to accomplish the desired network     structure, the 32-bit limit causes more and more aggravation.   Another major addressing system used in open internetworking is the   OSI method of specifying Network Service Access Points (NSAPs). The   NSAP consists of an authority and format identifier, a numberMcGovern & Ullmann                                              [Page 4]

RFC 1707                         CATNIP                     October 1994   assigned to that authority, an address assigned by that authority,   and a selector identifying the next layer (transport layer) protocol.   This is actually a general multi-level hierarchy, often obscured by   the details of specific profiles. (For example, CLNP doesn't specify   20 octet NSAPs, it allows any length. But various GOSIPs profile the   NSAP as 20 octets, and IS-IS makes specific assumptions about the   last 1-8 octets. And so on.)   The NSAP does not directly correspond to an IP address, as the   selector in IP is separate from the address. The concept that does   correspond is the NSAP less the selector, called the Network Entity   Title or NET. (An unfortunate acronym, but one we will use to avoid   repeating the full term.) The usual definition of NET is an NSAP with   the selector set to 0; the NET used here omits the 0 selector.   There is also a network numbering system used by IPX, a product of   Novell, Inc. (referred to from here on as Novell) and other vendors   making compatible software. While IPX is not yet well connected into   a global network, it has a larger installed base than either of the   other network layers.Network Layer Address   The network layer address looks like:      +----------+----------+---------------+---------------+      |  length  |   AFI    |  IDI ...      | DSP ...       |      +----------+----------+---------------+---------------+   The fields are named in the usual OSI terminology although that leads   to an oversupply of acronyms. Here are more detailed descriptions of   each field:   length: the number of bytes (octets) in the remainder of the           address.   AFI: the Authority and Format Identifier. A single byte        value, from a set of well-known values registered by        ISO, that determines the semantics of the IDI field   IDI: the Initial Domain Identifier, a number assigned by the        authority named by the AFI, formatted according to the        semantics implied by the AFI, that determines the        authority for the remainder of the address.   DSP: Domain Specific Part, an address assigned by the        authority identified by the value of the IDI.McGovern & Ullmann                                              [Page 5]

RFC 1707                         CATNIP                     October 1994   Note that there are several levels of authority. ISO, for example,   identifies (with the AFI) a set of numbering authorities (like X.121,   the numbering plan for the PSPDN, or E.164, the numbering plan for   the telephone system). Each authority numbers a set of organizations   or individuals or other entities. (For example, E.164 assigns   16172477959 to me as a telephone subscriber.)   The entity then is the authority for the remainder of the address. I   can do what I please with the addresses starting with (AFI=E.164)   (IDI=16172477959). Note that this is a delegation of authority, and   not an embedding of a data-link address (the telephone number) in a   network layer address. The actual routing of the network layer   address has nothing to do with the authority numbering.   The domain-specific part is variable length, and can be allocated in   whatever way the authority identified by the AFI+IDI desires.Network Layer Datagram   The common architecture format for network layer datagrams is   described below. The design is a balance between use on high   performance networks and routers, and a desire to minimize the number   of bits in the fixed header. Using the current state of processor   technology as a reference, the fixed header is all loaded into CPU   registers on the first memory cycle, and it all fits within the   operation bandwidth. The header leaves the remaining data aligned on   the header size (128 bits); with 64 bit addresses present and no   options it leaves the transport header 256 bit aligned.   On very slow and low performance networks, the fixed header is still   fairly small, and could be further compressed by methods similar to   those used with IP version 4 on links that consider every bit   precious. In between, it fits nicely into ATM cells and radio   packets, leaving sufficient space for the transport header and   application data.McGovern & Ullmann                                              [Page 6]

RFC 1707                         CATNIP                     October 1994      +---------------+---------------+-+-+-+-+-+-+-+-+---------------+      |   NLPID (70)  |  Header Size  |D|S|R|M|E| MBZ | Time to Live  |      +---------------+---------------+-+-+-+-+-+-+-+-+---------------+      |                 Forward Cache Identifier                      |      +---------------------------------------------------------------+      |                      Datagram Length                          |      +---------------------------------------------------------------+      |     Transport Protocol        |          Checksum             |      +---------------------------------------------------------------+      |               Destination Address ...                         |      +---------------------------------------------------------------+      |               Source Address ...                              |      +---------------------------------------------------------------+      |               Options ...                                     |      +---------------------------------------------------------------+  NLPID: The first byte (the network layer protocol identifier in OSI)         is an 8 bit constant 70 (hex). This corresponds to Internet         Version 7.  Header Length: The header length is a 8-bit count of the number of         32-bit words in the header. This allows the header to         be up to 1020 bytes in length.  Flags: This byte is a small set of flags determining the datagram         header format and the processing semantics. The last three bits         are reserved, and must be set to zero. (Note that the         corresponding bits in CLNP version 1 are 001, since this byte         is the version field. This may be useful.)  Destination Address Omitted: When the destination address omitted         (DAO) flag is zero, the destination address is present as shown         in the datagram format diagram. When a datagram is sent with         an FCI that identifies the destination and the DAO flag is         set, the address does not appear in the datagram.  Source Address Omitted: The source address omitted (SAO) flag is zero         when the source address is present in the datagram. When         datagram is sent with an FCI that identifies the source and the         SAO flag is set, the source address is omitted from the         datagram.  Report Fragmentation Done: When this bit (RFD) is set, an intermediate         router that fragments the datagram (because it is larger than         the next subnetwork MTU) should report the event with an ICMP         Datagram Too Big message. (Unlike IP version 4, which uses DF         for MTU discovery, the RFD flag allows the fragmented datagramMcGovern & Ullmann                                              [Page 7]

RFC 1707                         CATNIP                     October 1994         to be delivered.)  Mandatory Router Option: The mandatory router option (MRO) flag         indicates that routers forwarding the datagram must look at the         network header options.  If not set, an intermediate router         should not look at the header options.  (But it may anyway;         this is a necessary consequence of transparent network layer         translation, which may occur anywhere.)         The destination host, or an intermediate router doing         translation, must look at the header options regardless of         the setting of the MRO flag.         A router doing fragmentation will normally only use the F         flag in options to determine whether options should be copied         within the fragmentation code path. (It might also recognize         and elide null options.) If the MRO flag is not set, the router         may not act on an option even though it copies it properly         during fragmentation.         If there are no options present, MRO should always be zero, so         that routers can follow the no-option profile path in their         implementation.  (Remember that the presence of options cannot         be divided from the header length, since the addresses are         variable length.)  Error Report Suppression: The ERS flag is set to suppress the sending         of error reports by any system (whether host or router)         receiving or forwarding the datagram. The system may log the         error, increment network management counters, and take any         similar action, but ICMP error messages or CNLP error reports         must not be sent.         The ERS flag is normally set on ICMP messages and other network         layer error reports. It does not suppress the normal response         to ICMP queries or similar network layer queries (CNLP echo         request).         If both the RFD and ERS flags are set, the fragmentation report         is sent.  (This definition allows a larger range of         possibilities than simply over-riding the RFD flag would; a         sender not desiring this behavior can see to it that RFD is         clear.)  Time To Live: The time to live is a 8-bit count, nominally in seconds.         Each hop is required to decrement TTL by at least one. A hop         that holds a datagram for an unusual amount of time (more than         2 seconds, a typical example being a wait for a subnetworkMcGovern & Ullmann                                              [Page 8]

RFC 1707                         CATNIP                     October 1994         connection establishment) should subtract the entire waiting         time in seconds (rounded upward) from the TTL.  Forward Cache Identifier: Each datagram carries a 32 bit field, called         "forward cache identifier", that is updated (if the information         is available) at each hop. This field's value is derived from         ICMP messages sent back by the next hop router, a routing         protocol (e.g., RAP), or some other method. The FCI is used to         expedite routing decisions by preserving knowledge where         possible between consecutive routers. It can also be used to         make datagrams stay within reserved flows, circuits, and mobile         host tunnels. If an FCI is not available, this field must be         zero, the SAO and DAO flags must be clear, and both destination         and source addresses must appear in the datagram.  Datagram Length: The 32-bit length of the entire datagram in octets.         A datagram can therefore be up to 4294967295 bytes in overall         length.  Particular networks normally impose lower limits.  Transport Protocol: The transport layer protocol. For example, TCP is         6.  Checksum: The checksum is a 16-bit checksum of the entire header,         using the familiar algorithm used in IP version 4.  Destination: The destination address, a count byte followed by the         destination NSAP with the zero selector omitted. This field is         present only if the DAO flag is zero. If the count field is not         3 modulo 4 (the destination is not an integral multiple of         32-bit words) zero bytes are added to pad to the next multiple         of 32 bits. These pad bytes are not required to be ignored:         routers may rely on them being zero.  Source: The source address, in the same format as the destination.         Present only if the SAO flag is zero. The source is padded in         the same way as destination to arrive at a 32-bit boundary.  Options: Options may follow. They are variable length, and always         32-bit aligned. If the MRO flag in the header is not set,         routers will usually not look at or take action on any option,         regardless of the setting of the class field.Multicasting   The multicast-enable option permits multicast forwarding of the   CATNIP datagram on subnetworks that directly support media layer   multicasting. This is a vanishing species, even in 10 Mbps Ethernet,   given the increasing prevalence of switching hubs. It also (perhapsMcGovern & Ullmann                                              [Page 9]

RFC 1707                         CATNIP                     October 1994   more usefully) permits a router to forward the datagram on multiple   paths when a multicast routing algorithm has established such paths.   There is no option data.   Note that there is no special address space for multicasting in the   CATNIP. Multicast destination addresses can be allocated anywhere by   any administration or authority. This supports a number of differing   models of addressing. It does require that the transport layer   protocol know that the destination is multicast; this is desirable in   any case. (For example, the transport will probably want to set the   ERS flag.)   On an IEEE 802.x (ISO 8802.x) type media, the last 23 bits of the   address (not including the 0 selector) are used in combination with   the multicast group address assigned to the Internet to form the   media address when forwarding a datagram with the multicast enable   option from a router to an attached network provided that the   datagram was not received on that network with either multicast or   broadcast media addressing. A host may send a multicast datagram   either to the media multicast address (the IP catenet model,) or   media unicast to a router which is expected to repeat it to the   multicast address within the entire level I area or to repeat copies   to the appropriate end systems within the area on non-broadcast media   (the more general CLNP model.)Network Layer Translation   The objective of translation is to be able to upgrade systems, both   hosts and routers, in whatever order desired by their owners.   Organizations must be able to upgrade any given system without   reconfiguration or modification of any other, and existing hosts must   be able to interoperate essentially forever. (Non-CATNIP routers will   probably be effectively eliminated at some point, except where they   exist in their own remote or isolated corners.)   Each CATNIP system, whether host or router, must be able to recognize   adjacent systems in the topology that are (only) IP version 4, CLNP,   or IPX and call the appropriate translation routine just before   sending the datagram.OSI CNLP   The translation between CLNP and the CATNIP compressed form of the   datagrams is the simplest case for CATNIP, since the addresses are   the same and need not be extended. The resulting CATNIP datagrams may   omit the source and destination addresses as explained previously,   and may be mixed with uncompressed datagrams on the same subnetwork   link. Alternatively, a subnetwork may operate entirely in the CATNIP,McGovern & Ullmann                                             [Page 10]

RFC 1707                         CATNIP                     October 1994   converting all transit traffic to CATNIP datagrams, even if FCIs that   would make the compression effective are not available.   Similarly, all network datagram formats with CATNIP mappings may be   compressed into the common form, providing a uniform transit network   service, with common routing protocols (such as IS-IS).Internet Protocol   All existing version 4 numbers are defined as belonging to the   Internet by using a new AFI, to be assigned to IANA by the ISO. This   document uses 192 at present for clarity in examples; it is to be   replaced with the assigned AFI. The AFI specifies that the IDI is two   bytes long, containing an administrative domain number.   The AD (Administrative Domain), identifies an administration which   may be an international authority (such as the existing InterNIC), a   national administration, or a large multi-organization (e.g., a   government). The idea is that there should not be more than a few   hundred of these at first, and eventually thousands or tens of   thousands at most.   AD numbers are assigned by IANA. Initially, the only assignment is   the number 0.0, assigned to the InterNIC, encompassing the entire   existing version 4 Internet.   The mapping from/to version 4 IP addresses:      +----------+----------+---------------+---------------------+      |  length  |   AFI    |  IDI ...      | DSP ...             |      +----------+----------+---------------+---------------------+      |     7    |   192    |  AD number    | version 4 address   |      +----------+----------+---------------+---------------------+   While the address (DSP) is initially always the 4 byte, version 4   address, it can be extended to arbitrary levels of subnetting within   the existing Internet numbering plan. Hosts with DSPs longer than 4   bytes will not be able to interoperate with version 4 hosts.Novell IPX   The Internetwork Packet Exchange protocol, developed by Novell based   on the XNS protocol (Xerox Network System) has many of the same   capabilities as the Internet and OSI protocols. At first look, it   appears to confuse the network and transport layers, as IPX includes   both the network layer service and the user datagram service of the   transport layer, while SPX (sequenced packet exchange) includes the   IPX network layer and provides service similar to TCP or TP4. ThisMcGovern & Ullmann                                             [Page 11]

RFC 1707                         CATNIP                     October 1994   turns out to be mostly a matter of the naming and ordering of fields   in the packets, rather than any architectural difference.   IPX uses a 32-bit LAN network number, implicitly concatenated with   the 48-bit MAC layer address to form an Internet address. Initially,   the network numbers were not assigned by any central authority, and   thus were not useful for inter-organizational traffic without   substantial prior arrangement. There is now an authority established   by Novell to assign unique 32-bit numbers and blocks of numbers to   organizations that desire inter-organization networking with the IPX   protocol.   The Novell/IPX numbering plan uses an ICD, to be assigned, to   designate an address as an IPX address. This means Novell uses the   authority (AFI=47)(ICD=Novell) and delegates assignments of the   following 32 bits.   An IPX address in the common form looks like:      +----------+----------+---------------+---------------------+      |  length  |   AFI    |  IDI ...      | DSP ...             |      +----------+----------+---------------+---------------------+      |    13    | 47 (hex) |  Novell ICD   | network+MAC address |      +----------+----------+---------------+---------------------+   This will always be followed by two bytes of zero padding when it   appears in a common network layer datagram. Note that the socket   numbers included in the native form IPX address are part of the   transport layer.SIPP   It may seem a little odd to describe the interaction with SIPP-16   (version 6 of IP) which is another proposed candidate for the next   generation of network layer protocols. However, if SIPP-16 is   deployed, whether or not as the protocol of choice for replacement of   IP version 4, there will then be four network protocols to   accommodate.  It is prudent to investigate how SIPP-16 could then be   integrated into the common addressing plan and datagram format.   SIPP-16 defines 128 bit addresses, which are included in the NSAP   addressing plan under the Internet AFI as AD number 0.1. It is not   clear at this time what administration will hold the authority for   the SIPP-16 numbering plan. This produces a 20 byte NSAPA, with the   system ID field positioned exactly as expected by (e.g.) IS-IS.McGovern & Ullmann                                             [Page 12]

RFC 1707                         CATNIP                     October 1994      +----------+----------+---------------+---------------------+      |  length  |   AFI    |  IDI ...      | DSP ...             |      +----------+----------+---------------+---------------------+      |    19    |   192    |  AD (0.1)     |   SIPP-16 address   |      +----------+----------+---------------+---------------------+   The SIPP-16 addressing method (the definition of the 128 bits) will   not be described here.   The SIPP proposal also includes an encapsulated-tunnel proposal   called IPAE, to address some of the issues that are designed into   CATNIP.  The CATNIP direct translation does not use the SIPP-IPAE   packet formats. IPAE also specifies a "mapping table" for prefixes.   This table is kept up-to-date by periodic FTP transfers from a   "central site." The CATNIP definitions leave the problem of prefix   selection when converting into SIPP firmly within the scope of the   SIPP-IPAE proposal, and possible methods are not described here.   In translating from SIPP (IPv6) to CATNIP (IPv7), the only unusual   aspect is that SIPP defines some things that are normally considered   options to be "payloads" overloaded onto the transport protocol   numbering space.  Fortunately, the only one that need be considered   is fragmentation; a fragmented SIPP datagram may need to be   reassembled prior to conversion.  Other "payloads" such as routing   are ignored (translated verbatim) and will normally simply fail to   achieve the desired effect.   Translation to SIPP is simple, except for the difficult problem of   inventing the "prefix" if an implementation wants to support   translating Internet AD 0.0 numbers into the SIPP addressing domain.Internet DNS   CATNIP addresses are represented in the DNS with the NSAP RR. The   data in the resource record is the NSAP, including the zero selector   at the end. The zone file syntax for the data is a string of   hexadecimal digits, with a period "." inserted between any two octets   where desired for readability. For example:   The inverse (PTR) zone is .NSAP.INT, with the CATNIP address   (reversed).  That is, like .IN-ADDR.ARPA, but with .NSAP.INT instead.   The nibbles are represented as hexadecimal digits.   This respects the difference in actual authority: the IANA is the   authority for the entire space rooted in .IN-ADDR.ARPA. in the   version 4 Internet, while in the new Internet it holds the authority   only for 0.C.NSAP.INT. (Following the example of 192 as the AFI   value.) The domain 0.0.0.0.0.C.NSAP.INT is to be delegated by IANA toMcGovern & Ullmann                                             [Page 13]

RFC 1707                         CATNIP                     October 1994   the InterNIC. (Understanding that in present practice the InterNIC is   the operator of the authoritative root.)Security Considerations   The CATNIP design permits the direct use of the present proposals for   network layer security being developed in the IPSEC WG of the IETF.   There are a number of detailed requirements; the most relevant being   that network layer datagram translation must not affect (cannot   affect) the transport layers, since the TPDU is mostly inaccessible   to the router. For example, the translation into IPX will only work   if the port numbers are shadowed into the plaintext security header.References   [Chapin93]      Chapin, L., and D. Piscitello, "Open Systems                   Networking", Addison-Wesley, Reading, Massachusetts,                   1993.   [Perlman92]     Perlman, R., "Interconnections: Bridges and Routers"                   Addison-Wesley, Reading, Massachusetts, 1992.   [RFC791]        Postel, J., Editor, "Internet Protocol - DARPA                   Internet Program Protocol Specification", STD 5,RFC791 USC/Information Sciences Institute,  September                   1981.   [RFC792]        Postel, J., Editor, "Internet Control Message                   Protocol - DARPA Internet Program Protocol                   Specification", STD 5,RFC 792, USC/Information                   Sciences Institute, September 1981.   [RFC793]        Postel, J., Editor, "Transmission Control Protocol -                   DARPA Internet Program Protocol Specification,                   STD 7,RFC 793, USC/Information Sciences Institute,                   September, 1981.   [RFC801]        Postel, J., "NCP/TCP Transition Plan",RFC 801,                   USC/Information Sciences Institute, November, 1981.   [RFC1191]       Mogul, J., and S. Deering, "Path MTU Discovery",RFC 1191, DECWRL, Stanford University, November,                   1990.   [RFC1234]       Provan, D., "Tunneling IPX Traffic Through IP                   Networks",RFC 1234, Novell, Inc., June 1991.McGovern & Ullmann                                             [Page 14]

RFC 1707                         CATNIP                     October 1994   [RFC1247]       Moy, J., "OSPF Version 2",RFC 1247, Proteon, Inc.,                   July 1991.   [RFC1287]       Clark, D., Chapin, L., Cerf, V., Braden, R., and                   R. Hobby, "Towards the Future Internet Architecture",RFC 1287, MIT, BBN, CNRI, ISI, UCDavis, December,                   1991.   [RFC1335]       Wang, Z., and J. Crowcroft, "A Two-Tier Address                   Structure for the Internet: A Solution to the                   Problem of Address Space Exhaustion",RFC 1335,                   University College London, May 1992.   [RFC1338]       Fuller, V., Li, T., Yu, J., and K. Varadhan,                   "Supernetting: an Address Assignment and Aggregation                   Strategy",RFC 1338, BAARNet, cicso, Merit, OARnet,                   June 1992.   [RFC1347]       Callon, R., "TCP and UDP with Bigger Addresses                   (TUBA), A Simple Proposal for Internet Addressing                   and Routing",RFC 1347, DEC, June 1992.   [RFC1466]       Gerich, E., "Guidelines for Management of IP Address                   Space",RFC 1466, Merit, May 1993.   [RFC1475]       Ullmann, R., "TP/IX: The Next Internet",RFC 1475,                   Process Software Corporation, June 1993.   [RFC1476]       Ullmann, R., "RAP: Internet Route Access Protocol",RFC 1476, Process Software Corporation, June 1993.   [RFC1561]       Piscitello, D., "Use of ISO CLNP in TUBA                   Environments",RFC 1561, Core Competence, December                   1993.McGovern & Ullmann                                             [Page 15]

RFC 1707                         CATNIP                     October 1994Authors' Addresses   Michael McGovern   Sunspot Graphics   EMail: scrivner@world.std.com   Robert Ullmann   Lotus Development Corporation   1 Rogers Street   Cambridge, MA 02142   Phone: +1 617 693 1315   EMail: rullmann@crd.lotus.comMcGovern & Ullmann                                             [Page 16]