US20130128901A1 - Layer 1 frame construction - Google Patents

Abstract

A method includes appending, by a network device, a first layer1 frame header to a first payload to form a first layer1 frame and a second layer1 frame header to a second payload to form a second layer1 frame and outputting the first layer1 frame and the second layer1 frame in a same format to a network. The first payload may include first layer2 data. The first layer1 frame header may include a first protocol identifier that indicates that the first layer2 data is associated with a first protocol. The second payload may include second layer2 data. The second layer1 frame header may include a second protocol identifier that indicates that the second layer2 data is associated with a second, different protocol.

Description

RELATED APPLICATIONS
• This application is a continuation of U.S. patent application Ser. No. 12/543,200, filed Aug. 18, 2009, which is a continuation of U.S. patent application Ser. No. 11/326,437, filed Jan. 6, 2006, now U.S. Pat. No. 7,593,399, which is a continuation of U.S. patent application Ser. No. 09/733,940, filed Dec. 12, 2000, now U.S. Pat. No. 7,050,455, the disclosures of which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
• The present invention relates to a frame construction method which can accommodate STM (Synchronous Transfer Mode), ATM (Asynchronous Transfer Mode) and IP (Internet Protocol) by use of the same frame format and which can transfer a mixture of STM traffic and best effort traffic by use of the same frame format. The present invention also relates to a frame construction device for constructing such frames and a data transfer system for transferring such frames.
DESCRIPTION OF RELATED ART
• Conventional networks have been constructed mainly in the fields of circuit-switched networks (telephone networks (voice transmission telecommunication networks), etc.) and networks employing private (leased) lines. However, with the rapid progress of the Internet communication of nowadays, data networks, especially networks employing the IP (Internet Protocol), are growing in high speed. Therefore, the remarkable increase of Internet traffic via modems over voice channels is putting pressure on the usage status of the circuit-switched network systems.
• The IP data, after being switched (after being connected to an ISP (Internet Service Provider), is transferred in an IP network which is composed of leased lines and routers. Meanwhile, transfer capacity of data transfer systems in being increased by the speeding-up of SONET (Synchronous Optical NETwork)/SDH (Synchronous Digital Hierarchy) and the employment of DWDM (Dense Wavelength Division Multiplexing).
• Under such complex circumstances of today, networks of various types are constructed and managed independently, and the construction, management and maintenance of networks are becoming more and more complicated.
• In order to get rid of the complexity, techniques capable of accommodating the STM (Synchronous Transfer Mode), ATM (Asynchronous Transfer Mode) and IP (Internet Protocol) in a single packet transfer network are becoming necessary.
• Such a packet transfer network, in which packet-based data transfer is conducted, is required to transfer STM data of the conventional synchronous transfer mode together with ATM data of the asynchronous transfer mode, and is also required to have the end-to-end circuit quality monitoring functions (end-to-end performance monitoring) which have been provided to the conventional networks.
• Meanwhile, the packet transfer network is also needed to transfer high-priority traffic which is required by the next-generation packet communication, with the high quality level of the conventional STM signals.
• The next-generation packet communication has to satisfy the above conditions, therefore, a frame construction method which can accommodate the STM, ATM and IP by use of the same frame format is required today, and propositions of data transfer systems based on such a frame construction method are sought for.
• As a prior art concerning frame construction, the “Simple Data Link” protocol (SDL) has been disclosed in Internet Draft “draft-ietf-pppext-sdl-pol-00.txt”, 1999, Lucent Technologies, IETF (Internet Engineering Task Force).
• FIG. 1 is a schematic diagram showing a conventional frame format which is defined in the prior art (SDL). Referring toFIG. 1, the SDL frame format includes a header which is composed of two 2-byte fields “Packet Length” and “CRC16”. The “Packet Length” field (identifier) indicates the length of the packet (i.e. the payload of the frame), and the “CRC16” field (identifier) indicates the CRC (Cyclic Redundancy Check) result for the “Packet Length” field. The payload of the SDL frame is a variable-length field (0˜64 Kbytes).
• A device that received the SDL frame conducts the CRC operation for the header of the frame and thereby establishes byte synchronization and frame synchronization. By use of the SDL frame format, continuous transfer of variable-length packets of a single protocol is made possible.
• However, the above conventional SDL frame format can not transfer a mixture of signals of various protocols (a mixture of STM, ATM and IP, for example), since the conventional SDL frame format does not have functions for implementing periodical data transfer of the STM signals with fixed intervals nor does have information for designating transfer scheduling.
SUMMARY OF THE INVENTION
• It is therefore the primary object of the present invention to provide a frame construction method which can accommodate STM, ATM and IP by use of the same frame format and which can transfer a mixture of STM traffic and best effort traffic by use of the same frame format.
• One aspect is directed to a method. The method includes appending, by a network device, afirst layer1 frame header to a first payload to form afirst layer1 frame. The first payload may includefirst layer2 data ofmulti-protocol layer2 data received from a plurality of network devices. Thefirst layer1 frame header may include a first protocol identifier that indicates that thefirst layer2 data is associated with a first protocol. The method may also include appending, by the network device, asecond layer1 frame header to a second payload to form asecond layer1 frame. The second payload may includesecond layer2 data of themulti-protocol layer2 data. Thesecond layer1 frame header may include a second protocol identifier that indicates that thesecond layer2 data is associated with a second protocol that is different than the first protocol. A length of thefirst layer1 frame may be different from a length of thesecond layer1 frame. Further, the method may include outputting, from the network device, thefirst layer1 frame and thesecond layer1 frame in a same format to a network.
• Another aspect is directed to a device. The device may include one or more processors to append afirst layer1 frame header to a first payload to form afirst layer1 frame. The first payload may includefirst layer2 data ofmulti-protocol layer2 data received from a plurality of network devices. Thefirst layer1 frame header may include a first protocol identifier that indicates that thefirst layer2 data is associated with a first protocol. The one or more processors may append asecond layer1 frame header to a second payload to form asecond layer1 frame. The second payload may includesecond layer2 data of themulti-protocol layer2 data. Thesecond layer1 frame header may include a second protocol identifier that indicates that thesecond layer2 data is associated with a second protocol that is different from the first protocol. A length of thefirst layer1 frame may be different from a length of thesecond layer1 frame. The one or more processors may output thefirst layer1 frame and thesecond layer1 frame in a same format to a network.
• Yet another aspect is directed to a non-transitory computer-readable medium storing instructions. The instructions may include one or more instructions which, when executed by one or more processors, may cause the one or more processors to append afirst layer1 frame header to a first payload to form afirst layer1 frame. The first payload may include afirst layer2 data ofmulti-protocol layer2 data received from a plurality of network devices. Thefirst layer1 frame header may include a first protocol identifier that indicates that thefirst layer2 data is associated with a first protocol. The instructions may also include one or more instructions which, when executed by one or more processors, may cause the one or more processors to append asecond layer1 frame header to a second payload to form asecond layer1 frame. The second payload may includesecond layer2 data of themulti-protocol layer2 data. Thesecond layer1 frame header may include a second protocol identifier that indicates that thesecond layer2 data is associated with a second protocol that is different from the first protocol. A length of thefirst layer1 frame may be different from a length of thesecond layer1 frame. The instructions may also include one or more instructions which, when executed by one or more processors, may cause the one or more processors to output thefirst layer1 frame and thesecond layer1 frame in a same format to a network.
• In accordance with a 132nd aspect of the present invention, in the 88th aspect, the OAM frame is used by the edge node at the egress point for path monitoring.
BRIEF DESCRIPTION OF THE DRAWINGS
• The objects and features of the present invention will become more apparent from the consideration of the following detailed description taken in conjunction with the accompanying drawings, in which:
• FIG. 1 is a schematic diagram showing a conventional frame format which is defined in SDL (Simple Data Link);
• FIG. 2 is a schematic diagram showing a basic frame format of alayer1 frame in accordance with an embodiment of the present invention;
• FIG. 3 is a schematic diagram showing the correspondence between thebasic layer1 frame ofFIG. 1 and abasic layer2 frame in accordance with the embodiment of the present invention;
• FIG. 4A is a schematic diagram showing alayer1 frame in accordance with the embodiment of the present invention for transferring ATM cells;
• FIG. 4B is a schematic diagram showing alayer1 frame in accordance with the embodiment of the present invention for transferring an STM signal;
• FIG. 4C is a schematic diagram showing alayer1 frame in accordance with the embodiment of the present invention for transferring an IP packet;
• FIG. 5A is a schematic diagram showing the composition of the header of thelayer1 frame in accordance with the embodiment of the present invention;
• FIG. 5B is a table showing an example of codes which are used for a “Frame Mode” identifier of thelayer1 frame header ofFIG. 5A;
• FIG. 5C is a table showing an example of codes which are used for a “Stuff” identifier of thelayer1 frame header ofFIG. 5A;
• FIG. 5D is a table showing an example of codes which are used for a “Protocol” identifier of thelayer1 frame header ofFIG. 5A;
• FIG. 6 is a schematic diagram showing a case where a “Stuffing Length” identifier is added to thelayer1 frame header ofFIG. 5A when stuffing is executed;
• FIG. 7 is a schematic diagram showing the composition of thelayer1 frame when the stuffing is executed;
• FIG. 8A is a schematic diagram showing the basic composition of thelayer1 frame;
• FIG. 8B is a schematic diagram showing the composition of a BOM (Beginning Of Message) frame in accordance with the embodiment of the present invention;
• FIG. 8C is a schematic diagram showing the composition of a COM (Continuation Of Message) frame and an EOM (End Of Message) frame in accordance with the embodiment of the present invention;
• FIG. 9 is a schematic diagram showing an example of partitioning of thelayer2 frame in accordance with the embodiment of the present invention, in which alayer2 frame is partitioned into segments and distributing to a BOM frame, two COM frames and an EOM frame;
• FIG. 10 is a schematic diagram showing an example of frame-multiplexedlayer1 frames in accordance with the embodiment of the present invention, in which a besteffort IP layer2 frame is partitioned into segments and distributed to a BOM frame and an EOM frame;
• FIG. 11 is a schematic diagram showing an example of frame-multiplexedlayer1 frames in accordance with the embodiment of the present invention, in which a besteffort IP layer2 frame is partitioned into segments and distributed to a BOM frame, a COM frame and an EOM frame;
• FIG. 12 is a schematic diagram showing an example of a network as a data transfer system in accordance with the embodiment of the present invention;
• FIG. 13 is a schematic diagram showing the transfer of anIP layer1 frame by use of a route label in accordance with the embodiment of the present invention;
• FIG. 14 is a schematic diagram showing the transfer of anIP layer1 frame by use of a flow label in accordance with the embodiment of the present invention;
• FIG. 15 is a block diagram showing an example of the internal composition of a transmission section of a edge node of the data transfer system ofFIG. 12;
• FIG. 16 is a block diagram showing an example of the internal composition of a reception section of the edge node;
• FIG. 17 is a block diagram showing an example of the internal composition of a core node of the data transfer system ofFIG. 12;
• FIG. 18 is a block diagram showing an example of the internal composition of a reception section of the core node;
• FIG. 19 is a block diagram showing an example of the internal composition of a transmission section of the core node;
• FIG. 20 is a schematic diagram showing link monitoring and path monitoring which are conducted in the embodiment of the present invention;
• FIG. 21 is a flow chart showing an algorithm in accordance with the embodiment of the present invention for the transmission of besteffort IP layer1 frames;
• FIG. 22A is a schematic diagram showing the composition of a dummy frame which is employed in the embodiment of the present invention;
• FIG. 22B is a schematic diagram showing the composition of a minimal dummy frame which is employed in the embodiment of the present invention; and
• FIG. 22C is a schematic diagram showing the composition of an OAM (Operating And Management) frame which is employed in the embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Referring now to the drawings, a description will be given in detail of preferred embodiments in accordance with the present invention.
• The frame in accordance with an embodiment of the present invention, which is designed to accommodate STM (Synchronous Transfer Mode) signals, ATM (Asynchronous Transfer Mode) cells and IP packets in the same frame format, is implemented by alayer1 frame and alayer2 frame which is contained in thelayer1 frame. Thelayer1 frame is a variable-length frame which enables variable-length packet transfer.
• The header of thelayer1 frame includes a “Packet Length” identifier, a “Priority” identifier, a “Protocol” identifier, a “Frame Mode” identifier, a “Stuff” identifier and a “Header CRC16” identifier as shown inFIG. 5A. The “Packet Length” identifier indicates the length of a packet (the payload of thelayer1 frame). The “Priority” identifier indicates the priority of the packet. The “Protocol” identifier indicates alayer2 protocol (STM, ATM, IP, etc.). The “Frame Mode” identifier indicates the type of thelayer1 frame, that is, the correspondence between thelayer1 frame and thelayer2 frame contained therein. The “Stuff” identifier indicates whether stuff data (data for stuffing) is included in thelayer1 frame or not. The “Header CRC16” identifier indicates the result of 16-bit CRC (Cyclic Redundancy Check) operation for the previous fields (the “Packet Length” identifier, the “Priority” identifier, the “Protocol” identifier, the “Frame Mode” identifier and the “Stuff” identifier).
• When the stuffing is not executed, thelayer1 frame includes a “Payload” field (hereafter, referred to as a “layer1 frame payload” or a “payload”) just after the header as shown inFIG. 8A. Thelayer1 frame payload is a variable-length field (0˜64 Kbytes). After the “payload, thelayer1 frame includes a “Payload CRC” field which indicates the result of CRC operation for thelayer1 frame payload.
• Also when the stuffing is executed, thelayer1 frame includes a payload after the header as shown inFIG. 7. Thelayer1 frame payload is a variable-length field (0˜64 Kbytes). In this case, a “Stuffing Length” identifier for indicating the length of the stuff data is provided to the top of thelayer1 frame payload. The stuff data is inserted at the end of thelayer1 frame payload. The stuff data is data for adjusting the length of thelayer1 frame. The length of the stuff data is described in the “Stuffing Length” identifier at the transmitting end. After the payload, thelayer1 frame includes a “Payload CRC” field which indicates the result of CRC operation for thelayer1 frame payload.
• The “Header CRC16” identifier of thelayer1 frame header enables a device that receives thelayer1 frame to establish bit synchronization, byte synchronization and frame synchronization. The “Payload CRC” field is used for monitoring payload data quality. Therefore, thelayer1 frame enables a device at the receiving end to conduct bit synchronization, byte synchronization, frame synchronization and payload data quality monitoring. In short, thelayer1 frame according to the present invention can implement the basic functions of theconventional layer1.
• Theaforementioned layer2 frame of this embodiment is packed in the payload of thelayer1 frame. Thelayer2 frame can accommodate and transfer multi-protocol data (STM signals, ATM cells, IP packets, etc.). The protocol of the data contained in thelayer2 frame is indicated by the “Protocol” identifier of thelayer1 frame header.
• The above multiprotocol includes ATM, STM, IPv4 (Internet Protocol version 4), IPv6 (Internet Protocol version 6), MPLS (MultiProtocol Label Switching), etc.
• The header of thelayer2 frame is placed at the top of thelayer1 frame payload. Incidentally, in the case where the stuffing is executed (that is, in the case where the “Stuffing Length” identifier is placed at the top of thelayer1 frame payload), thelayer2 frame header is placed after the “Stuffing Length” identifier. The length of thelayer2 frame header can be changed depending on the protocol of the data which is contained and transferred in thelayer2 frame.
• Here, we define two types of labels as the header of thelayer2 frame in the case where an IP packet is transferred in thelayer1 frame: a route label and a flow label. The route label is a field to be referred to in the routing through nodes of a network. The flow label is a field to be used for selecting one OCH (Optical CHannel) (defined by a transmission line and a wavelength) to be used when there are two or more OCHs between two nodes. Further, as a special-purpose layer1 frame for monitoring a path between the ingress point and the egress point of a network, an OAM (Operating And Management) frame is defined.
• In cases where an STM signal or ATM cells are transferred in thelayer1 frame, the route label can be used for the label information in thelayer2 frame header for the routing of thelayer1 frame. In these cases, the flow label is not used, since the amounts of STM traffic and ATM traffic are smaller than that of IP traffic and the transfer of thelayer1 frames for STM and ATM can be conducted by use of a preset wavelength between nodes.
• In the following, an explanation will be given on the segmentation of thelayer2 frame. The following explanation will be given assuming that thelayer2 frame is required to transfer CBR (Constant Bit Rate) traffic such as STM signals. Incidentally, in ordinary data transfer, onelayer2 frame corresponds to onelayer1 frame.
• In ordinary packet-based data transfer such as POS (Packet Over Sonet, RFC2615 [Internet Engineering Task Force]), frames containing CBR traffic have to be transferred with a constant cycle (125 μsec).
• However, the transfer of a CBR traffic frame is generally suspended until the transfer of apervious layer2 frame (alayer2 frame containing best effort traffic etc.) is finished. Therefore, the STM signals can not be transferred with a constant cycle in ordinary packet-based data transfer, since each packet is a variable-length packet.
• In order to avoid such a problem, in the frame construction method of this embodiment, along layer2 frame of a low priority is partitioned into segments and distributed to two ormore layer1 frames.
• Ahigh priority layer1 frame (such as the CBR traffic) is forcibly transferred by means of interruption even if alow priority layer2 frames are being transferred.
• Thelayer1 frames containing the partitionedlayer2 frames can be classified into three types: BOM (Beginning Of Message) frames, COM (Continuation Of Message) frames and EOM (End Of Message) frames. The BOM frame is alayer1 frame containing the front end of alayer2 frame. The EOM frame is alayer1 frame containing the rear end of alayer2 frame. The COM frame is alayer1 frame which contains a partitioned segment of alayer2 frame but does not contain the front end not rear end of thelayer2 frame. In short, alow priority layer2 frame (from its front end to rear end) is partitioned into segments and distributed to a BOM frame, one or more (or zero) COM frames and an EOM frame.
• Whether alayer1 frame is a frame including the partitioned segments of alayer2 frame (BOM frame, COM frame or EOM frame) or not (single frame) can be judged by referring to the “Frame Mode” identifier which is included in thelayer1 frame header.
• A device that terminates thelayer1 frames refers to the “Priority” identifiers and the “Protocol” identifier in the headers of thelayer1 frames and thereby extractslayer1 frames having the same “Priority” identifier and “Protocol” identifier. By such operation, a BOM frame, COM frames and an EOM frame containing segments of a partitionedlayer2 frame are received and transferred successively, thereby theoriginal layer2 frame can be reconstructed (recombined and restored) easily.
• In the frame construction method of this embodiment, there are cases where thelayer2 frame header of alayer1 frame is omitted. When alayer2 frame is partitioned into segments and distributed to a BOM frame, COM frames and an EOM frame, header information to be held by the COM frames and the EOM frame is the same as that of the BOM frame. Therefore, omission of thelayer2 frame header information is allowed in the COM frames and the EOM frame of this embodiment. In other words, the BOM frame contains thelayer2 frame header, however, the COM frames and the EOM frame are not provided with thelayer2 frame headers. Thus, the BOM frame is called an “uncompressed frame”, whereas the COM frames and the EOM frame are called “compressed frames”.
• In the following, an explanation will be given on data transfer by use of aggregate frames in accordance with the embodiment of the present invention.
• Thelayer2 frame of this embodiment is capable of accommodating and transferring two or more data units when transferring data of an upper-layer protocol (STM, ATM, IP, MPLS, etc.)
• For example, the STM signals are transferred in units of N bytes (not in units of bytes). By assigning each byte to a 64 Kbps channel, an N-channel trunk signal of N×64 Kbps is transferred between two conventional switches.
• In this case, a network edge device (such as an edge node) for generating thelayer2 frames collects STM data in units of 125 μsec and packs them in thelayer2 frames. Similarly, for transmitting ATM signals, the network edge device packs a plurality of ATM cells in alayer2 frame and transmits thelayer2 frame.
• In the following, periodical STM signal transfer (at fixed intervals of 125 μsec) which is conducted in this embodiment will be explained.
• Whenlayer1 frames containing STM signals (hereafter, also referred to as “STM layer1 frames”) have to be transferred at fixed intervals, the length of alayer1 frame which is transferred before theSTM layer1 frame becomes important.
• For instance, even when there are nolayer1 frames to be transferred before theSTM layer1 frame, bit synchronization, byte synchronization and frame synchronization which are implemented by thelayer1 frames has to be maintained. In such cases, a dummy frame is transferred before theSTM layer1 frame and thereby an idle transfer space between theSTM layer1 frames are filled up.
• Whether alayer1 frame is a dummy frame or not can be judged by referring to the “Protocol” identifier of thelayer1 frame header. The dummy frame is a variable-length frame.
• When the idle transfer space before the transfer of anSTM layer1 frame is shorter than a shortest dummy frame (minimal dummy frame), the aforementioned stuff data is inserted in alayer1 frame that is transferred before the idle transfer space, thereby the idle transfer space is filled up and thelayer1 frames become continuous.
• The length of the stuff data is shorter than that of the minimal dummy frame. The minimal dummy frame is composed of thelayer1 frame header and the “Payload CRC” field, therefore, the stuff data length is shorter than the length of thelayer1 frame header and the length of the “Payload CRC” field added together. Concretely, the stuff data length becomes several bytes.
• By the insertion of the dummy frames and the stuff data, the continuous transfer of thelayer1 frames are realized, the frame synchronization can be maintained, and the periodical transfer of theSTM layer1 frames at precisely fixed intervals (125 μsec) is made possible.
• FIG. 2 is a schematic diagram showing the basic frame format of thelayer1 frame in accordance with the embodiment of the present invention. As shown inFIG. 2, thelayer1 frame includes thelayer1 frame header (6 byte) and thelayer1 frame payload (0˜64 Kbytes). The “Payload CRC” field, indicating the result of CRC16 or CRC32 operation for thelayer1 frame payload, is added optionally.
• FIG. 3 is a schematic diagram showing the correspondence between thebasic layer1 frame and abasic layer2 frame. Referring toFIG. 3, thelayer2 frame is composed of alayer2 header (L2 header) and a data section. As shown inFIG. 3, thelayer2 frame corresponds to the payload (0˜64 Kbytes) of thelayer1 frame.
• FIGS. 4A through 4C are schematic diagrams showing frames in accordance with the embodiment of the present invention when ATM cells, STM signals and IP packets are packed in thelayer2 frames.
• In the payload of thelayer1 frame which is shown inFIG. 4A, alayer2 frame, including a header (L2 header) and a plurality of ATM cells having the same VPI (Virtual Path Identifier), is packed.
• In the payload of thelayer1 frame which is shown inFIG. 4B, alayer2 frame, including a header (L2 header) and STM signals (N×64 Kbps voice data addressed to the same destination) is packed.
• In the payload of thelayer1 frame which is shown inFIG. 4C, alayer2 frame, including a header (L2 header) and an IP packet, is packed.
• FIG. 5A is a schematic diagram showing the composition of the header of thelayer1 frame in accordance with the embodiment of the present invention. As shown inFIG. 5A, thelayer1 frame header (L1 header) includes the “Packet Length” identifier, the “Priority” identifier, the “Protocol” identifier, the “Frame Mode” identifier, the “Stuff” identifier and the “Header CRC16” identifier. In the case where the stuff data is inserted in thelayer1 frame payload, the “Stuffing Length” identifier indicating the length of the stuff data is added to thelayer1 frame header.
• The “Packet Length” identifier indicates the length of the payload of thelayer1 frame. The “Priority” identifier indicates the priority of thelayer1 frame. The “Protocol” identifier indicates a protocol of the data contained in thelayer2 frame. The “Frame Mode” identifier indicates a method for packing alayer2 frame in one ormore layer1 frames, that is, whether thelayer1 frame is a single frame, a BOM frame, a COM frame or an EOM frame. The “Stuff” identifier indicates whether the stuff data exists in thelayer1 frame or not. The “Header CRC16” identifier indicates the result of 16-bit CRC (Cyclic Redundancy Check) operation for the above fields (identifiers). The “Stuffing Length” identifier indicates the length of the stuff data.
• FIG. 5B is a table showing an example of codes which are used for the “Frame Mode” identifier. Referring toFIG. 5B, the “Frame Mode” identifiers (codes) “00”, “01”, “10” and “11” denote a single frame, a BOM frame, a COM frame and an EOM frame, respectively.
• FIG. 5C is a table showing an example of codes which are used for the “Stuff” identifier. Referring toFIG. 5C, the “Stuff” identifier (code) “0” indicates that the stuffing is not executed, and the “Stuff” identifier (code) “1” indicates that the stuffing is executed.
• FIG. 5D is a table showing an example of codes which are used for the “Protocol” identifier. Referring toFIG. 5D, the “Protocol” identifiers (code) “000”, “001”, “010”, “011”, “100”, “101” denote IPv4, IPv6, STM, ATM, OAM, and a dummy frame, respectively.
• As shown inFIGS. 6 and 7, the “Stuffing Length” identifier is added to thelayer1 frame header when the stuffing is executed and the stuff data is inserted in the bottom of thelayer1 frame payload.
• In the following, a data transfer method for transferring thelayer1 frames of this embodiment will be explained. Whenlayer1 frames containing STM signals (STM layer1 frames) andlayer1 frames containing ATM cells (hereafter, referred to as “ATM layer1 frames”) are transferred, theSTM layer1 frames and theATM layer1 frames are transmitted periodically.Layer1 frames containing IP packets (hereafter, referred to as “IP layer1 frames”) are accommodated in remaining spaces between theSTM layer1 frames and theATM layer1 frames.
• In this embodiment, there are two priority levels with regard to the IP packets: a primary IP packet and a best effort IP packet. The primary IP packet is an IP packet whose bandwidth has to be guaranteed or whose delay is required to be short (delay-sensitive). The primary IP packet is transferred with higher priority than the best effort IP packet.
• Therefore, theSTM layer1 frames and theATM layer1 frames are transmitted at predetermined periods, and thelayer1 frames containing the primary IP packets (hereafter, referred to as “primary IP layer1 frames”) and thelayer1 frames containing the best effort IP packets (hereafter, referred to as “besteffort IP layer1 frames”) are successively transmitted in between theSTM layer1 frames and theATM layer1 frames.
• When the transmission of a variable-length best effort IP packet (contained in a besteffort IP layer2 frame in a besteffort IP layer1 frame) overlapped with the periodical transmission of the STM/ATM layer2 frames (contained in the STM/ATM layer1 frames), the besteffort IP layer2 frame is partitioned into segments and distributed to two or more besteffort IP layer1 frames. The besteffort IP layer1 frames containing the partitioned segments of a besteffort IP layer2 frame include a BOM frame, COM frames and an EOM frame, as mentioned before.
• FIG. 10 is a schematic diagram showing an example of frame-multiplexedlayer1 frames in accordance with the embodiment, in which a besteffort IP layer2 frame is partitioned into segments and distributed to a BOM frame and an EOM frame. Referring toFIG. 10, a besteffort IP layer2 frame is partitioned into two segments and distributed to a BOM (Beginning Of Message) frame (alayer1 frame containing the front end of thelayer2 frame) and an EOM (End Of Message) frame (alayer1 frame containing the rear end of thelayer2 frame).
• FIG. 11 is a schematic diagram showing an example of frame-multiplexedlayer1 frames in accordance with the embodiment, in which a besteffort IP layer2 frame is partitioned into segments and distributed to a BOM frame, a COM frame and an EOM frame. Referring toFIG. 11, a besteffort IP layer2 frame is partitioned into three segments and distributed to a BOM frame, a COM (Continuation Of Message) frame (alayer1 frame containing a partitioned segment of alayer2 frame but not containing the front end or rear end of thelayer2 frame) and an EOM (End Of Message) frame. As shown inFIG. 9, the number of COM frames between a BOM frame and an EOM frame is not limited to one. Two or more COM frames can be generated between the BOM frame and the EOM frame depending on the length of the besteffort IP layer2 frame. When thelayer2 frame to be partitioned is short, no COM frames are generated between the BOM frame and the EOM frame, as shown inFIG. 10.
• Referring toFIGS. 10 and 11, iflayer1 frames having the same “Priority” identifier and “Protocol” identifier are extracted, the BOM frame, the COM frames and the EOM frame containing the partitioned segments of alayer2 frame are received and transferred in sequence.
• A device receiving and terminating thelayer1 frames can discriminate between a BOM frame, a COM frame, an EOM frame and a single frame by referring to the “Frame Mode” identifier which is included in the header of thelayer1 frame (seeFIG. 5B).
• If the “Frame Mode” identifier is “00” (single frame), a best effort IP packet has been packed in thelayer1 frame without being partitioned.
• If the “Frame Mode” identifier is “01” (BOM frame), a best effort IP packet has been partitioned into two or more segments, and thelayer1 frame contains the first segment (front end) of the best effort IP packet.
• If the “Frame Mode” identifier is “10” (COM frame), a best effort IP packet has been partitioned into two or more segments, and thelayer1 frame contains a segment of the best effort IP packet that is not the first segment not the last segment.
• If the “Frame Mode” identifier is “11” (EOM frame), a best effort IP packet has been partitioned into two or more segments, and thelayer1 frame contains the last segment (rear end) of the best effort IP packet.
• The BOM frame, the COM frames and the EOM frame are transferred successively and a device at the receivingend extracts layer1 frames having the same “Priority” identifier and “Protocol” identifier, therefore, when the device received a COM frame or an EOM frame (“Frame Mode” identifier: “10” or “11”), the device can judge that the COM/EOM frame can be used together with a previously received BOM frame for reconstructing alayer2 frame.
• Therefore, in this embodiment, thelayer2 frame contained in a COM frame or an EOM frame is not provided with alayer2 frame header. By the omission of thelayer2 frame header in the COM/EOM frames, the payloads of thelayer2 frames can be made longer in the COM/EOM frames, thereby the amount of transferred information can be increased.
• The frame format of thelayer1 frame will be explained in detail referring toFIGS. 8A through 8C.FIG. 8A is a schematic diagram showing the basic composition of thelayer1 frame of this embodiment. Referring toFIG. 8A, the header of thelayer1 frame includes the “Packet Length” identifier, the “Priority” identifier, the “Protocol” identifier, the “Frame Mode” identifier (unshown inFIG. 8A), the “Stuff” identifier (unshown inFIG. 8A) and the “Header CRC16” identifier. The payload of thelayer1 frame is placed in a variable-length field (0˜64 Kbytes) after the header. After the payload, a “Payload CRC16” field or a “Payload CRC32” field is added as an option.
• FIG. 8B is a schematic diagram showing the composition of the BOM frame of this embodiment. In the BOM frame as an uncompressed frame, thelayer2 frame header (the route label and the flow label) and thelayer2 frame payload (data area) are packed in thelayer1 frame payload.
• FIG. 8C is a schematic diagram showing the composition of the COM/EOM frame of this embodiment. In the COM/EOM frame as a compressed frame, only thelayer2 frame payload (data area) are packed in thelayer1 frame payload. Thelayer2 frame header (the route label and the flow label) are omitted.
• In this embodiment, thelayer1 frames containing STM signals (STM layer1 frames) are transferred at fixed intervals (125 μsec) as shown inFIGS. 10 and 11. A switching section of a node (which relays thelayer1 frames) transmits the STM signals (STM layer1 frames) as traffic of the highest priority.
• For the implementation of the periodical transmission of theSTM layer1 frames, alayer1 frame containing a best effort IP packet (besteffort IP layer1 frame) has to be partitioned into a BOM frame, COM frames and an EOM frame when the transmission of the besteffort IP layer1 frame overlaps with the transmission of anSTM layer1 frame. Incidentally, a BOM/COM/EOM frame which will be used in the following explanation is a besteffort IP layer1 frame. TheSTM layer1 frame, theATM layer1 frame and theprimary IP layer1 frame are not partitioned and transferred as single frames.
• However, the periodical transmission of theSTM layer1 frames can not be realized only by the partitioning of the besteffort IP layer1 frame and the high priority transmission of theSTM layer1 frames.
• As shown inFIGS. 10 and 11, theSTM layer1 frames are transferred with the highest priority at fixed intervals (125 μsec), andlayer1 frames containing ATM cells (ATM layer1 frames) andlayer1 frames containing primary IP packets (primary IP layer1 frames) are also transferred with high priority. Therefore, the besteffort IP layer1 frames have to be transferred in transfer spaces (idle time) between theSTM layer1 frames, theATM layer1 frames and theprimary IP layer1 frames.
• The length L of the transfer space (idle time) in which the besteffort IP layer1 frame can be transferred (hereafter, referred to as a “best effort IP transfer space”) changes depending on the lengths of theATM layer1 frames and theprimary IP layer1 frames. The transfer of theSTM layer1 frames has to be conducted at predetermined periods as mentioned above. Therefore, the length of the besteffort IP layer1 frame has to be adjusted to the length L of the best effort IP transfer space.
• In the following, an operation of a device at the transmitting end for filling up the best effort IP transfer space (to the length: L) by use of a dummy frame or stuff data will be explained referring toFIGS. 7,21,22A and22B.
• The aforementioned dummy frame is alayer1 frame whose payload is filled with null data as shown inFIG. 22A. A dummy frame whose null area is 0 Kbyte is the aforementioned “minimal dummy frame”. The minimal dummy frame is composed of thelayer1 frame header and the “Payload CRC” field only, as shown inFIG. 22B.
• The stuff data is data which is inserted into the besteffort IP layer1 frame payload for adjusting the length of the besteffort IP layer1 frame to the length L of the best effort IP transfer space (seeFIG. 7). As shown inFIG. 7, the stuff data is added after the data area of the payload of the besteffort IP layer1 frame. In the case where the stuff data is added to the besteffort IP layer1 frame payload, the “Stuffing Length” identifier is provided to the top of the payload. In this case, code “1” is described in the “Stuff” identifier of the header as shown inFIGS. 5C and 7.
• FIG. 21 is a flow chart showing an algorithm in accordance with this embodiment for the transmission of the besteffort IP layer1 frames. Incidentally, the following explanation will be given ignoring the “Payload CRC” field for the sake of simplicity.
• When a device at the transmitting end (hereafter, referred to as a “frame transmission device”) received a besteffort IP layer1 frame transmission instruction and a parameter L indicating the length L of the best effort IP transfer space, the frame transmission device first judges whether or not a remaining EOM frame exists (step S2200). If a remaining EOM frame exists (“Yes” in the step S2200), the length M of the EOM frame is compared with the length L of the best effort IP transfer space (step S2201).
• If the EOM frame length M is longer than the best effort IP transfer space length L (“M>L” in the step S2201), the EOM frame is partitioned and the first segment of the EOM frame is extracted. The length of the extracted first segment (including a header) is set to L. The extracted first segment of the EOM frame is transmitted as a COM frame, and the remaining segment of the EOM frame is stored as an EOM frame (having alayer1 frame header) (step S2202), thereby the process is ended.
• If the EOM frame length M is equal to the best effort IP transfer space length L (“M=L” in the step S2201), the EOM frame is transmitted without being partitioned (step S2203), thereby the process is ended.
• If the EOM frame length M is shorter than the best effort IP transfer space length L (“M<L” in the step S2201), the EOM frame length M and the minimal dummy frame length D added together (M+D) is compared with the best effort IP transfer space length L (step S2204).
• If the length M+D is equal to the best effort IP transfer space length L (“M+D=L” in the step S2204), the EOM frame of the length M is transmitted (step S2207) and thereafter the minimal dummy frame of the length D is transmitted (step S2208), thereby the process is ended.
• If the length M+D is longer than the best effort IP transfer space length L (“M+D>L” in the step S2204), the stuff data is inserted after the payload of the EOM frame. The length of the stuff data is set to L−M−1 bytes. Incidentally, the 1 byte is used for the “Stuffing Length” identifier which indicates the length of the stuff data. Therefore, in the EOM frame to be transmitted, the “Stuffing Length” identifier (1 byte) is inserted at the top of thelayer1 frame payload and the stuff data (L−M−1 bytes) is inserted at the bottom of thelayer1 frame payload as shown inFIG. 7 (step S2205). Thereafter, the EOM frame is transmitted (step S2206), and thereby the process is ended.
• If the length M+D is shorter than the best effort IP transfer space length L (“M+D<L” in the step S2204), the EOM frame is transmitted and the value of the parameter L (best effort IP transfer space length L) is updated into L−M (L−M→L) (step S2209).
• If no remaining EOM frame exists (“No” in the step S2200) or if the update of the best effort IP transfer space length L has been conducted (step S2209), the frame transmission device judges whether a besteffort IP layer1 frame to be transferred next exists or not (step S2210).
• If no besteffort IP layer1 frame to be transmitted next exists (“No” in the step S2210), a dummy frame of the length L is transmitted so as to implement the periodical transmission of theSTM layer1 frames (step S2211), thereby the process is ended.
• If a besteffort IP layer1 frame to be transmitted next exists (“Yes” in the step S2210), the frame transmission device obtains the length B of the besteffort IP layer1 frame to be transmitted next (step S2212).
• Subsequently, the besteffort IP layer1 frame length B is compared with the best effort IP transfer space length L (step S2213).
• If the besteffort IP layer1 frame length B is longer than the best effort IP transfer space length L (“B>L” in the step S2213), the besteffort IP layer1 frame is partitioned into a BOM frame of the length L and an EOM frame (step S2214). Thereafter, the BOM frame of the length L is transmitted and the EOM frame (having alayer1 frame header) is stored (step S2215), thereby the process is ended.
• If the besteffort IP layer1 frame length B is equal to the best effort IP transfer space length L (“B=L” in the step S2213), the besteffort IP layer1 frame is transmitted as a single frame without being partitioned (step S2216), thereby the process is ended.
• If the besteffort IP layer1 frame length B is shorter than the best effort IP transfer space length L (“B<L” in the step S2213), the besteffort IP layer1 frame length B and the minimal dummy frame length D added together (B+D) is compared with the best effort IP transfer space length L (step S2217).
• If the length B+D is equal to the best effort IP transfer space length L (“B+D=L” in the step S2217), the besteffort IP layer1 frame of the length B is transmitted as a single frame (step S2219) and thereafter the minimal dummy frame of the length D is transmitted (step S2220), thereby the process is ended.
• If the length B+D is longer than the best effort IP transfer space length L (“B+D>L” in the step S2217), the stuff data is inserted after the payload of the besteffort IP layer1 frame to be transmitted next. The length of the stuff data is set to L−B−1 bytes. The 1 byte is used for the “Stuffing Length” identifier indicating the length of the stuff data. Therefore, in the besteffort IP layer1 frame to be transmitted next, the “Stuffing Length” identifier (1 byte) is inserted at the top of thelayer1 frame payload and the stuff data (L−B−1 bytes) is inserted at the bottom of thelayer1 frame payload as shown inFIG. 7 (step S2221). Thereafter, the besteffort IP layer1 frame is transmitted as a single frame (step S2222), and thereby the process is ended.
• If the length B+D is shorter than the best effort IP transfer space length L (“B+D<L” in the step S2217), the besteffort IP layer1 frame is transmitted as a single frame and the value of the parameter L (best effort IP transfer space length L) is updated into L−B (L−B→L) (step S2218). Thereafter, the process is returned to the step S2212.
• By the processes which has been described above, the best effort IP transfer space of the length L is precisely filled up and thereby the periodical transmission of theSTM layer1 frames is realized successfully. Therefore, the STM signals can be transferred end-to-end through the packet-based network.
• In the following, an explanation will be given on thelayer2 frame header in accordance with this embodiment referring toFIGS. 4C,8B,13 and14.
• In the case where an IP packet is transferred in alayer2 frame, thelayer2 frame is provided with theaforementioned layer2 frame header which is composed of the route label and the flow label, as shown inFIG. 4C.
• The route label is a field which is referred to for the routing through nodes of the network. The flow label is a field which is used for designating one OCH (Optical CHannel) (transmission line and wavelength) to be used when there are two or more OCHs between two nodes.
• As mentioned before, in the case of the besteffort IP layer1 frames, the route label and the flow label as thelayer2 frame header are added to the BOM frames only as shown inFIG. 8B, and are not added to the COM frames and the EOM frames as shown inFIG. 8C.FIGS. 13 and 14 show the transfer ofIP layer1 frames by use of the route label and the flow label. Details of frame transfer process using the route label and the flow label will be described later.
• The “Payload CRC” field of thelayer1 frame can realize link quality monitoring (as shown in (B) and (D) ofFIG. 20) but can not be used for path monitoring. Therefore, an OAM (Operating And Management) frame which is shown inFIG. 22C can be employed for the path monitoring between the ingress point and the egress point in the network as shown in (B) and (E) ofFIG. 20. The path monitoring can be executed by filling the payload of the OAM frame shown inFIG. 22C with the so-called “PN pattern”, for example. The OAM frames can be transferred at the ends of the fixed intervals (125 μsec). When the OAM frames are used, the best effort IP transfer space length L which was used in the flow chart ofFIG. 21 is decreased by the length of the OAM frame.
• As described above, in the frame construction method in accordance with the embodiment of the present invention, theSTM layer1 frames are transferred at fixed periods (125 μsec). Bit synchronization is established in the physical layer, and byte synchronization and frame synchronization are established by use of the “Header CRC16” identifier, thereby the STM signals are necessarily transferred at fixed intervals (125 μsec) maintaining the end-to-end circuit quality monitoring functions (end-to-end performance monitoring functions).
• Further, the STM signals, the ATM cells and the IP packets are transferred by use of a common frame format, therefore, the different types of information can be handled and managed in a network concurrently by a common method.
• Therefore, the STM networks, the ATM networks and the IP networks which have been constructed separately and independently can be integrated or constructed as a common or integrated network.
• By the definition of the route label and the flow label as transfer information for theIP layer2 frames, IP packets can be transferred appropriately by simple procedures even when each link is composed of two or more wavelengths by means of WDM (Wavelength Division Multiplexing). The details of the transfer of theIP layer1 frames by use of the route label and the flow label will be described later.
• In the following, a data transfer system for transferring a mixture of the STM traffic and the best effort traffic in accordance with the embodiment of the present invention will be explained in detail.
• FIG. 12 is a schematic diagram showing an example of a network as a data transfer system in accordance with the embodiment of the present invention. The network shown inFIG. 12 includes STM devices (STM switch, STM transmission node, etc.)1100 and1111, ATM devices (ATM switch, ATM crossconnect, etc.)1101 and1112,IP routers1102 and1113, edge nodes (ENs)1103,1106,1108 and1110, and core nodes (CNs)1104,1105,1107 and1109.
• Theedge nodes1103,1106,1108 and1110 of the network are connected to conventional network devices such as theSTM devices1100 and1111, theATM devices1101 and1112, theIP routers1102 and1113, etc. Therefore, theedge nodes1103,1106,1108 and1110 operate as the interfaces of the network to conventional network devices.
• The edge node (1103,1106,1108,1110) packs STM signals, ATM cells and IP packets inlayer2 frames (inlayer1 frames) as shown inFIGS. 4A through 4C and transmits thelayer1 frames to the network.
• Meanwhile, the edge node (1103,1106,1108,1110) receives and terminateslayer1 frames which are transferred from the network and extracts STM signals, ATM cells and IP packets from thelayer1 frames. The extracted STM signals, ATM cells and IP packets are transmitted to theSTM devices1100 and1111, theATM devices1101 and1112, and theIP routers1102 and1113, respectively.
• The core node (1104,1105,1107,1109) terminateslayer1 frames and extractslayer2 frames from thelayer1 frames. The core node (1104,1105,1107,1109) executes switching of thelayer2 frames based on the header information of the extractedlayer2 frames. Thereafter, the core node (1104,1105,1107,1109) converts thelayer2 frames intolayer1 frames and outputs thelayer1 frames to appropriate lines based on the header information.
• FIG. 15 is a block diagram showing an example of the internal composition of a transmission section of the edge node (1103,1106,1108,1110). In the following, the composition and the operation of the transmission section of the edge node (1103,1106,1108,1110) will be described in detail referring toFIG. 15.
• The transmission section of the edge node (1103,1106,1108,1110) shown inFIG. 15 includes an IPpacket reception section1403, an ATMcell reception section1404, an STMsignal reception section1405, a routelabel generation section1406, a flowlabel generation section1407, anIP layer2frame generation section1408, anATM layer1frame generation section1409, anSTM layer1frame generation section1410, atimer1411, anIP layer1frame generation section1412, ascheduler section1413 and aframe multiplexing section1414.
• The STMsignal reception section1405 receives STM signals from anSTM device1402 for assemblingSTM layer2 frames. The STM signal, whose destination is recognized by provisioning, is an N-channel voice signal. The bit rate of each channel is set to 8 bit/125 μsec (64 Kbps), therefore, the bit rate of the STM signal becomes N×64 Kbps.
• The STMsignal reception section1405 sends the STM signals to theSTM layer1frame generation section1410. TheSTM layer1frame generation section1410 first generatesSTM layer2 frames by formingSTM layer2 frame payloads collecting the STM signals in units of 125 μsec and adding alayer2 frame header including a route label to eachSTM layer2 frame payload, and thereafter generatesSTM layer1 frames by adding “Packet Length” identifiers (indicating the length of theSTM layer1 frame payload), “Priority” identifiers (indicating CBR (Constant Bit Rate) data transfer), “Protocol” identifiers (indicating STM), “Frame Mode” identifiers (indicating “Single Frame”) and “Stuff” identifiers (indicating “No Stuffing”) to theSTM layer2 frames. Incidentally, the route label of theSTM layer2 frame is generated by theSTM layer1frame generation section1410 by provisioning. Concretely, STM frames containing the STM signals are supplied from theSTM device1402, and the destination of each STM signal is judged based on the position of a time slot (containing the STM signal) in the STM frame. TheSTM layer2 frame is generated by collecting STM signals for the same destination, and a route label corresponding to the destination is provided to theSTM layer2 frame header, for example.
• Subsequently, theSTM layer1frame generation section1410 conducts the CRC16 operation to the header of the generatedSTM layer1 frame and adds the result to the bottom of theSTM layer1 frame header. Further, as an option, theSTM layer1frame generation section1410 conducts the CRC16 or CRC32 to thelayer1 frame payload and adds the result to the rear end of theSTM layer1 frame.
• The ATMcell reception section1404 receives ATM cells from anATM device1401 for assemblingATM layer2 frames and stores the ATM cells in theATM layer1frame generation section1409.
• TheATM layer1frame generation section1409 first generatesATM layer2 frames by formingATM layer2 frame payloads by use of the stored ATM cells and adding alayer2 frame header including a route label to eachATM layer2 frame payload, and thereafter generatesATM layer1 frames by adding “Packet Length” identifiers (indicating the length of theATM layer1 frame payload), “Priority” identifiers (indicating types of the ATM (CBR (Constant Bit Rate), UBR (Unspecified Bit Rate), etc.)), “Protocol” identifiers (indicating ATM), “Frame Mode” identifiers (indicating “Single Frame”) and “Stuff” identifiers (indicating “No Stuffing”) to theATM layer2 frames. Incidentally, the route label of theATM layer2 frame is generated by theATM layer1frame generation section1409 based on the VPI/VCI of the ATM cell header, for example.
• Subsequently, theATM layer1frame generation section1409 conducts the CRC16 operation to the header of the generatedATM layer1 frame and adds the result to the bottom of theATM layer1 frame header. Further, as an option, theATM layer1frame generation section1409 conducts the CRC16 or CRC32 to thelayer1 frame payload and adds the result to the rear end of theATM layer1 frame.
• The IPpacket reception section1403 receives IP packets from anIP router1400 for assemblingIP layer2 frames and stores the IP packets in theIP layer2frame generation section1408. Meanwhile, header information of the IP packets is sent to the routelabel generation section1406 and the flowlabel generation section1407.
• The routelabel generation section1406 generates a route label based on the destination IP address or based on the destination IP address and the source IP address which are contained in the IP packet header, and sends the result (route label) to theIP layer2frame generation section1408.
• The flowlabel generation section1407 generates a flow label based on the header information of the IP packet and sends the generated flow label to theIP layer2frame generation section1408.
• TheIP layer2frame generation section1408 generatesIP layer2 frames by use of the IP packets, the route labels and the flow labels. The generatedIP layer2 frames are sent to theIP layer1frame generation section1412 and stored therein.
• TheIP layer1frame generation section1412 separates the storedIP layer2 frames intoprimary IP layer2 frames and besteffort IP layer2 frames. Whether anIP layer2 frame is aprimary IP layer2 frame or a besteffort IP layer2 frame can be determined by referring to the COS (Class Of Service) identifier of the IP packet header, or by judging whether or not the IP packet header includes registered IP address information concerning primary IP, for example. TheIP layer1frame generation section1412 generatesprimary IP layer1 frames and besteffort IP layer1 frames by use of theprimary IP layer2 frames and the besteffort IP layer2 frames respectively, and outputs theprimary IP layer1 frames to theframe multiplexing section1414 with higher priority than the besteffort IP layer1 frames.
• TheIP layer1frame generation section1412 partitions the besteffort IP layer1 frame into the BOM frame, the COM frames and the EOM frame according to the method which has been described referring to the flow chart ofFIG. 21. TheIP layer1frame generation section1412 inserts the stuff data to the besteffort IP layer1 frame if necessary according to the above method.
• The judgment on whether the besteffort IP layer1 frame should be transmitted as a single frame or should be partitioned into a BOM frame, COM frames and an EOM frame, and the judgment on whether the stuff data should be inserted or not are conducted depending on the length L of the best effort IP transfer space, as explained referring to the flow chart ofFIG. 21.
• TheIP layer1frame generation section1412 generates a “Packet Length” identifier (indicating the length of the besteffort IP layer1 frame payload), a “Priority” identifier (indicating low priority), a “Protocol” identifier (indicating IP), a “Frame Mode” identifier (indicating a single frame, a BOM frame, a COM frame or an EOM frame) and a “Stuff” identifier (indicating whether or not stuff data exists) as the besteffort IP layer1 frame header.
• Subsequently, theIP layer1frame generation section1412 conducts the CRC16 operation to the generated besteffort IP layer1 frame header and adds the result (“Header CRC16” identifier) to the bottom of the besteffort IP layer1 frame header.
• In the case where the stuff data is inserted in the besteffort IP layer1 frame, theIP layer1frame generation section1412 adds the “Stuffing Length” identifier (indicating the length of the stuff data) after the “Header CRC16” identifier and inserts the stuff data at the bottom of the besteffort IP layer1 frame payload as shown inFIG. 7.
• Further, as an option, theIP layer1frame generation section1412 conducts the CRC16 or CRC32 to the besteffort IP layer1 frame payload and adds the result to the rear end of the besteffort IP layer1 frame.
• The besteffort IP layer1 frames generated by theIP layer1frame generation section1412 is outputted to theframe multiplexing section1414 with lower priority than theprimary IP layer1 frames. Incidentally, for theprimary IP layer1 frames, theIP layer1frame generation section1412 generates a “Packet Length” identifier (indicating the length of theprimary IP layer1 frame payload), a “Priority” identifier (indicating high priority), a “Protocol” identifier (indicating IP), a “Frame Mode” identifier (indicating a single frame), a “Stuff” identifier (indicating “No Stuffing”) and a “Header CRC16” identifier. Theprimary IP layer1 frames as single frames are outputted to theframe multiplexing section1414 with higher priority than the besteffort IP layer1 frames.
• Thescheduler section1413 instructs theSTM layer1frame generation section1410 to output anSTM layer1 frame to theframe multiplexing section1414 periodically (125 μsec) based on internal time which is clocked by thetimer1411.
• After letting theSTM layer1frame generation section1410 output theSTM layer1 frame to theframe multiplexing section1414, thescheduler section1413 instructs theATM layer1frame generation section1409 to output one ormore ATM layer1 frames stored therein to theframe multiplexing section1414.
• After letting theATM layer1frame generation section1409 output theATM layer1 frames to theframe multiplexing section1414, thescheduler section1413 instructs theIP layer1frame generation section1412 to output one or moreprimary IP layer1 frames stored therein to theframe multiplexing section1414 as single frames.
• After letting theIP layer1frame generation section1412 output theprimary IP layer1 frames to theframe multiplexing section1414, thescheduler section1413 instructs theIP layer1frame generation section1412 to output a besteffort IP layer1 frame stored therein to theframe multiplexing section1414 as a single frame, a BOM frame, a COM frame or an EOM frame. TheIP layer1frame generation section1412 outputs one or more besteffort IP layer1 frames according to the algorithm which has been explained referring to the flow chart ofFIG. 21.
• Theframe multiplexing section1414 receives theSTM layer1 frames, theATM layer1 frames, theprimary IP layer1 frames and the besteffort IP layer1 frames which are supplied from theSTM layer1frame generation section1410, theATM layer1frame generation section1409 and theIP layer1frame generation section1412 according to the instructions of thescheduler section1413, and frame multiplexes thelayer1 frames as shown inFIGS. 10 and 11. The frame-multiplexedlayer1 frames are outputted by theframe multiplexing section1414 to a transmission line (to a core node (1104,1105,1107,1109)).
• FIG. 16 is a block diagram showing an example of the internal composition of a reception section of the edge node (1103,1106,1108,1110). In the following, the composition and the operation of the reception section of the edge node (1103,1106,1108,1110) will be described in detail referring toFIG. 16.
• The reception section of the edge node (1103,1106,1108,1110) shown inFIG. 16 includes an IPpacket transmission section1503, an ATMcell transmission section1504, an STMsignal transmission section1505,frame termination sections1506,1507 and1508, and aframe separation section1509.
• Theframe separation section1509 establishes bit synchronization, byte synchronization and frame synchronization by use of thelayer1 frame headers.
• After establishing the bit synchronization, the byte synchronization and the frame synchronization, theframe separation section1509 refers to the “Protocol” identifier contained in the header of alayer1 frame and thereby judges whether the data contained in the payload of thelayer1 frame is an STM signal, an ATM cell or an IP packet.
• Subsequently, theframe separation section1509 refers to the “Packet Length” identifier of thelayer1 frame header and thereby grasps the total length and the rear end of thelayer1 frame payload.
• When thelayer1 frame is anSTM layer1 frame, theframe separation section1509 sends theSTM layer1 frame to theframe termination section1508. When thelayer1 frame is anATM layer1 frame, theframe separation section1509 sends theATM layer1 frame to theframe termination section1507. When thelayer1 frame is anIP layer1 frame, theframe separation section1509 sends theIP layer1 frame to theframe termination section1506.
• Theframe termination section1508 extracts STM signals from thelayer1 frames and sends the extracted STM signals to the STMsignal transmission section1505. The STMsignal transmission section1505 transmits the STM signals to anSTM device1502.
• Theframe termination section1507 extracts ATM cells from thelayer1 frames and sends the extracted ATM cells to the ATMcell transmission section1504. The ATMcell transmission section1504 transmits the ATM cells to anATM device1501.
• Theframe termination section1506 extracts anIP layer2 frame from theIP layer1 frame if theIP layer1 frame is a single frame. If the stuff data has been inserted in theIP layer2 frame, theframe termination section1506 removes the stuff data from theIP layer2 frame. Subsequently, thetermination section1506 extracts an IP packet from theIP layer2 frame and sends the extracted IP packet to the IPpacket transmission section1503. The IPpacket transmission section1503 transmits the IP packet to anIP router1500.
• If thelayer1 frame is a BOM frame or a COM frame, theframe termination section1506 stores the BOM/COM frame until an EOM frame is supplied from theframe separation section1509. When the EOM frame is supplied from theframe separation section1509, theframe termination section1506 reconstructs alayer2 frame by connecting the payloads of the BOM frame, the COM frames and the EOM frame. In the reconstruction of thelayer2 frame, theframe termination section1506 judges whether or not the stuff data has been inserted in each of thelayer1 frames. If the stuff data has been inserted in alayer1 frame, theframe termination section1506 removes the stuff data from thelayer1 frame.
• Subsequently, theframe termination section1506 extracts an IP packet from the reconstructedlayer2 frame and sends the extracted IP packet to the IPpacket transmission section1503. The IPpacket transmission section1503 transmits the IP packet to theIP router1500.
• FIG. 17 is a block diagram showing an example of the internal composition of the core node (1104,1105,1107,1109). In the following, the composition and the operation of the core node (1104,1105,1107,1109) will be described in detail referring toFIG. 17.
• The core node (1104,1105,1107,1109) shown inFIG. 17 includesreception sections1600 and1601, alayer2frame switch1602, andtransmission sections1603 and1604.
• The reception section (1600,1601) establishes byte synchronization and frame synchronization with regard to each input line by use of the “Header CRC16” identifiers in thelayer1 frame headers.
• Thelayer2frame switch1602 determines an appropriate output line (output port) for each frame based on the label information of thelayer2 frame header and thereby conducts frame switching. The transmission section (1603,1604) reconstructslayer1 frames for the transmission of thelayer2 frames into the appropriate output line.
• FIG. 18 is a block diagram showing an example of the internal composition of the reception section (1600,1601) of the core node (1104,1105,1107,1109). In the following, the composition and the operation of the reception section (1600,1601) of the core node (1104,1105,1107,1109) will be described in detail referring toFIG. 18.
• The reception section (1600,1601) of the core node (1104,1105,1107,1109) shown inFIG. 18 includes alayer1termination section1700, anSTM layer2termination section1701, anATM layer2termination section1702, anIP layer2termination section1703, aframe multiplexing section1704 and a priority processing scheduler1705.
• Thelayer1termination section1700 terminateslayer1 frames which are supplied from a transmission line. Thelayer1termination section1700 determines the type (STM, ATM or IP packet) of thelayer1 frame based on the “Protocol” identifier in thelayer1 frame header, and sends thelayer1 frame to theSTM layer2termination section1701, theATM layer2termination section1702 or theIP layer2termination section1703 depending on the type of thelayer1 frame.
• TheSTM layer2termination section1701 extracts anSTM layer2 frame from theSTM layer1 frame supplied from thelayer1termination section1700. In the same way, theATM layer2termination section1702 extracts anATM layer2 frame from theATM layer1 frame supplied from thelayer1termination section1700.
• TheIP layer2termination section1703 extracts anIP layer2 frame from theIP layer1 frame supplied from thelayer1termination section1700 if theIP layer1 frame is a single frame. If theIP layer1 frame is a BOM frame or a COM frame, theIP layer2termination section1703 stores the BOM/COM frame until an EOM frame is supplied from thelayer1termination section1700.
• When the EOM frame is supplied from thelayer1termination section1700, theIP layer2termination section1703 reconstructs anIP layer2 frame by connecting the payloads of the BOM frame, the COM frames and the EOM frame.
• In the extraction of theIP layer2 frame from theIP layer1 frame, theIP layer2termination section1703 refers to the “Stuff” identifier of theIP layer1 frame header and thereby judges whether or not the stuff data has been inserted in theIP layer1 frame. If the stuff data has been inserted in theIP layer1 frame, theIP layer2termination section1703 removes the stuff data (of a length which is described in the “Stuffing Length” identifier) from the payload of theIP layer1 frame.
• The priority processing scheduler1705 grasps the presence or absence oflayer2 frames stored in theSTM layer2termination section1701, theATM layer2termination section1702 and theIP layer2termination section1703 and conducts the management of priority processing.
• If anSTM layer2 frame, to be handled with the highest priority, exists in theSTM layer2termination section1701, the priority processing scheduler1705 instructs theframe multiplexing section1704 to read out theSTM layer2 frame with the highest priority.
• Thereafter, if one ormore ATM layer2 frames, to be handled with the second priority, exist in theATM layer2termination section1702, the priority processing scheduler1705 instructs theframe multiplexing section1704 to read out theATM layer2 frames.
• Thereafter, if one or moreprimary layer2 frames, to be handled with the third priority, exist in theIP layer2termination section1703, the priority processing scheduler1705 instructs theframe multiplexing section1704 to read out theprimary IP layer2 frames from theIP layer2termination section1703 if noATM layer2 frame exists in theATM layer2termination section1702.
• The besteffort IP layer2 frame is alayer2 frame of the lowest priority, therefore, the priority processing scheduler1705 instructs theframe multiplexing section1704 to read out the besteffort IP layer2 frames from theIP layer2termination section1703 only when there is noSTM layer2 frame,ATM layer2 frame norprimary IP layer2 frame in the reception section (1600,1601).
• Theframe multiplexing section1704 reads out thelayer2 frames from theSTM layer2termination section1701, theATM layer2termination section1702 and theIP layer2termination section1703 according to the instructions of the priority processing scheduler1705 and sends thelayer2 frames to thelayer2frame switch1602.
• FIG. 19 is a block diagram showing an example of the internal composition of the transmission section (1603,1604) of the core node (1104,1105,1107,1109). In the following, the composition and the operation of the transmission section (1603,1604) of the core node (1104,1105,1107,1109) will be described in detail referring toFIG. 19.
• The transmission section (1603,1604) of the core node (1104,1105,1107,1109) shown inFIG. 19 includes aframe multiplexing section1800, anSTM layer1frame generation section1801, anATM layer1frame generation section1802, anIP layer1 frame generation section1803, aframe separation section1804 and atransmission scheduler1805.
• Theframe separation section1804 receives thelayer2 frame from thelayer2frame switch1602 and sends thelayer2 frame to theSTM layer1frame generation section1801, theATM layer1frame generation section1802 or theIP layer1 frame generation section1803 depending on the protocol (STM, ATM, IP, etc.) of thelayer2 frame. Incidentally, information concerning the protocol of eachlayer2 frame is supplied from the reception section (1600,1601) via thelayer2frame switch1602 as control information. The control information can be transferred in the core node (1104,1105,1107,1109) by multiplexing with thelayer2 frames.
• Thetransmission scheduler1805 grasps the presence or absence oflayer2 frames stored in theSTM layer1frame generation section1801, theATM layer1frame generation section1802 and theIP layer1 frame generation section1803 and conducts the management of priority processing.
• Thetransmission scheduler1805 instructs theSTM layer1frame generation section1801 to output anSTM layer1 frame periodically (125 μsec).
• TheSTM layer1frame generation section1801 converts the storedSTM layer2 frame into anSTM layer1 frame and sends theSTM layer1 frame to theframe multiplexing section1800. Incidentally, information necessary for generating thelayer1 frame header can be transferred in the core node (1104,1105,1107,1109) as the aforementioned control information.
• In the conversion from theSTM layer2 frame to theSTM layer1 frame, theSTM layer1frame generation section1801 inserts theSTM layer2 frame in the payload of theSTM layer1 frame and inserts a “Packet Length” identifier, a “Priority” identifier (indicating CBR (Constant Bit Rate) data transfer), a “Protocol” identifier (indicating STM), a “Frame Mode” identifier (indicating “Single Frame”) and a “Stuff” identifier (indicating “No Stuffing”) in the header of theSTM layer1 frame. TheSTM layer1frame generation section1801 conducts CRC16 operation to theabove STM layer1 frame header and adds the result to the bottom of theSTM layer1 frame header. Further, as an option, theSTM layer1frame generation section1801 conducts the CRC16 or CRC32 to theSTM layer1 frame payload and adds the result to the rear end of theSTM layer1 frame.
• TheATM layer1frame generation section1802 converts the storedATM layer2 frame into anATM layer1 frame by inserting theATM layer2 frame in the payload of theATM layer1 frame and inserting a “Packet Length” identifier, a “Priority” identifier (indicating the type of ATM (CBR, UBR, etc.)), a “Protocol” identifier (indicating ATM), a “Frame Mode” identifier (indicating “Single Frame”) and a “Stuff” identifier (indicating “No Stuffing”) in the header of theATM layer1 frame. TheATM layer1frame generation section1802 conducts CRC16 operation to theabove ATM layer1 frame header and adds the result to the bottom of theATM layer1 frame header. Further, as an option, theATM layer1frame generation section1802 conducts the CRC16 or CRC32 to theATM layer1 frame payload and adds the result to the rear end of theATM layer1 frame.
• TheIP layer1 frame generation section1803 separates theIP layer2 frames intoprimary IP layer2 frames and besteffort IP layer2 frames, generatesprimary IP layer1 frames and besteffort IP layer1 frames by use of theprimary IP layer2 frames and the besteffort IP layer2 frames respectively, and outputs theprimary IP layer1 frames and the besteffort IP layer1 frames to theframe multiplexing section1800 giving higher priority to theprimary IP layer1 frames.
• TheIP layer1 frame generation section1803 partitions the besteffort IP layer1 frame (or the besteffort IP layer2 frame) into segments and distributes to a BOM frame, COM frames and an EOM frame if necessary according to the method which has been described referring toFIG. 21. TheIP layer1 frame generation section1803 inserts the stuff data to the besteffort IP layer1 frame if necessary according to the above method.
• The judgment on whether the besteffort IP layer1 frame should be transmitted as a single frame or should be partitioned into a BOM frame, COM frames and an EOM frame, and the judgment on whether the stuff data should be inserted or not are conducted depending on the length L of the best effort IP transfer space, as explained referring toFIG. 21.
• TheIP layer1 frame generation section1803 generates a “Packet Length” identifier (indicating the length of the besteffort IP layer1 frame payload), a “Priority” identifier (indicating low priority), a “Protocol” identifier (indicating IP), a “Frame Mode” identifier (indicating a single frame, a BOM frame, a COM frame or an EOM frame) and a “Stuff” identifier (indicating whether or not stuff data exists) as the besteffort IP layer1 frame header.
• Subsequently, theIP layer1 frame generation section1803 conducts the CRC16 operation to the generated besteffort IP layer1 frame header and adds the result (“Header CRC16” identifier) to the bottom of the besteffort IP layer1 frame header.
• In the case where the stuff data is inserted in the besteffort IP layer1 frame, theIP layer1 frame generation section1803 adds the “Stuffing Length” identifier (indicating the length of the stuff data) after the “Header CRC16” identifier and inserts the stuff data at the bottom of the besteffort IP layer1 frame payload as shown inFIG. 7.
• Further, as an option, theIP layer1 frame generation section1803 conducts the CRC16 or CRC32 to the besteffort IP layer1 frame payload and adds the result to the rear end of the besteffort IP layer1 frame.
• The besteffort IP layer1 frames generated by theIP layer1 frame generation section1803 is outputted to theframe multiplexing section1800 with lower priority than theprimary IP layer1 frames. Incidentally, for theprimary IP layer1 frames, theIP layer1 frame generation section1803 generates a “Packet Length” identifier (indicating the length of theprimary IP layer1 frame payload), a “Priority” identifier (indicating high priority), a “Protocol” identifier (indicating IP), a “Frame Mode” identifier (indicating a single frame), a “Stuff” identifier (indicating “No Stuffing”) and a “Header CRC16” identifier. Theprimary IP layer1 frames as single frames are outputted to theframe multiplexing section1800 with higher priority than the besteffort IP layer1 frames.
• Thetransmission scheduler1805 instructs theSTM layer1frame generation section1801 to output anSTM layer1 frame to theframe multiplexing section1800 periodically (125 μsec).
• After letting theSTM layer1frame generation section1801 output theSTM layer1 frame to theframe multiplexing section1800, thetransmission scheduler1805 instructs theATM layer1frame generation section1801 to output one ormore ATM layer1 frames stored therein to theframe multiplexing section1414.
• After letting theATM layer1frame generation section1802 output theATM layer1 frames to theframe multiplexing section1800, thetransmission scheduler1805 instructs theIP layer1 frame generation section1803 to output one or moreprimary IP layer1 frames stored therein to theframe multiplexing section1800 as single frames.
• After letting theIP layer1 frame generation section1803 output theprimary IP layer1 frames to theframe multiplexing section1800, thetransmission scheduler1805 instructs theIP layer1 frame generation section1803 to output a besteffort IP layer1 frame stored therein to theframe multiplexing section1800 as a single frame, a BOM frame, a COM frame or an EOM frame. TheIP layer1 frame generation section1803 outputs one or more besteffort IP layer1 frames according to the algorithm which has been explained referring to the flow chart ofFIG. 21.
• Theframe multiplexing section1800 receives theSTM layer1 frames, theATM layer1 frames, theprimary IP layer1 frames and the besteffort IP layer1 frames supplied from theSTM layer1frame generation section1801, theATM layer1frame generation section1802 and theIP layer1 frame generation section1803, and frame multiplexes thelayer1 frames as shown inFIGS. 10 and 11. The frame-multiplexedlayer1 frames are outputted by theframe multiplexing section1800 to a transmission line.
• FIG. 20 is a schematic diagram showing link monitoring and path monitoring which are conducted in this embodiment.FIG. 20 shows an example of frame transfer betweenedge nodes1900 and1904 viacore nodes1901,1902 and1903.
• As shown (B) ofFIG. 20, link monitoring with regard to each link between two nodes is conducted by each node (1901,1902,1903,1904) by referring to the “Payload CRC” field of eachlayer1 frame which is shown in (D) ofFIG. 20.
• As shown (C) ofFIG. 20, path monitoring with regard to a path from the ingress point to the egress point can be conducted by theedge node1904 at the egress point by referring to the OAM frame which is shown in (E) ofFIG. 20 (seeFIG. 22C). As mentioned before, the so-called PN pattern can be packed in the payload of the OAM frame, for example.
• As described above, in the data transfer system and the frame construction devices in accordance with the embodiment of the present invention, theSTM layer1 frames are transferred at fixed periods (125 μsec). Bit synchronization is established in the physical layer, and byte synchronization and frame synchronization are established by use of the “Header CRC16” identifier, thereby the STM signals are necessarily transferred at fixed intervals (125 μsec) maintaining the end-to-end circuit quality monitoring functions (end-to-end performance monitoring functions).
• Further, the STM signals, the ATM cells and the IP packets are transferred by use of a common frame format, therefore, the different types of information can be handled and managed in a network concurrently by a common method.
• Especially, the core node (1104,1105,1107,1109) establishes the bit synchronization, the byte synchronization and the frame synchronization by referring to thelayer1 frame headers, and theSTM layer1 frames, theATM layer1 frames and theIP layer1 frames are outputted to appropriate output lines by use of thelayer2frame switch1602.
• Therefore, the STM networks, the ATM networks and the IP networks which have been constructed separately and independently can be integrated or constructed as a common or integrated network.
• By the definition of the route label and the flow label as transfer information for theIP layer2 frames, IP packets can be transferred appropriately by simple procedures even when each link is composed of two or more wavelengths by means of WDM (Wavelength Division Multiplexing).
• In the following, the operation of the data transfer system in accordance with the embodiment of the present invention for transferring a mixture of the STM traffic and the best effort traffic will be explained more in detail.
• First, the transfer of STM signals in the data transfer system ofFIG. 12 will be explained in detail.
• Referring toFIG. 15, in the transmission section of theedge node1103, the STMsignal reception section1405 receives STM frames (containing STM signals) from the STM device1402 (1100) and stores the STM frames. The STMsignal reception section1405 terminates thelayer1 which is used between theSTM device1402 and theedge node1103, extracts the STM signals from the STM frames, and sends the STM signals to theSTM layer1frame generation section1410.
• Thelayer1 between the STM device1100 (1402) and theedge node1103 is implemented by conventional specifications such as SDH (Synchronous Digital Hierarchy), PDH (Plesiochronous Digital Hierarchy), etc.
• The STM signals are converted intolayer2 frames by theSTM layer1frame generation section1410. Concretely, the 64 Kbps×N channel voice signal (8 bits/125 μsec for each channel), whose destination is recognized by the STM device1100 (1402) by provisioning, is packed in thelayer2 frame payload. Alayer2 frame header corresponding to the destination of the STM signals is added to thelayer2 frame payload by theSTM layer1frame generation section1410, thereby theSTM layer2 frame which is shown inFIG. 4B is generated.
• Subsequently, theSTM layer1frame generation section1410 generates anSTM layer1 frame header including the “Packet Length” identifier (indicating the length of theSTM layer1 frame payload), the “Priority” identifier (indicating CBR data transfer), the “Protocol” identifier (indicating STM), the “Frame Mode” identifier (indicating “Single Frame”) and the “Stuff” identifier (indicating “No Stuffing”), and adds thelayer1 frame header to thelayer2 frame. Incidentally, in theSTM layer1 frames, the “Frame Mode” identifier is always set to “00” (Single Frame) and the “Stuff” identifier is always set to “0” (No Stuffing) (seeFIGS. 5B and 5C).
• The CRC16 operation is conducted to thelayer1 frame header and the result is added to the bottom of thelayer1 frame header. As an option, the CRC16 or CRC32 is conducted to thelayer1 frame payload and the result is added to the rear end of thelayer1 frame.
• By the above process, anSTM layer1 frame having the basic frame format shown inFIG. 2 is formed. More concretely, thelayer2 frame shown inFIG. 3A (containing thelayer2 frame header and thelayer2 frame payload in which the STM signals are packed) is packed in theSTM layer1 frame payload as shown inFIG. 4B, and the above identifiers shown inFIG. 5A are packed in theSTM layer1 frame header.
• Thescheduler section1413 of theedge node1103 grasps whether or not layer1 frames to be transferred exist in theSTM layer1frame generation section1410, theATM layer1frame generation section1409 and theIP layer1frame generation section1412.
• When anSTM layer1 frame to be transferred is stored in theSTM layer1frame generation section1410, thescheduler section1413 instructs theSTM layer1frame generation section1410 tooutput STM layer1 frames periodically (125 μsec). According to the instructions of thescheduler section1413, theSTM layer1frame generation section1410 outputs theSTM layer1 frames to theframe multiplexing section1414 periodically (125 μsec).
• Theframe multiplexing section1414 frame multiplexes theSTM layer1 frames from theSTM layer1frame generation section1410 withlayer1 frames supplied from theATM layer1frame generation section1409 and theIP layer1frame generation section1412, and transmits the frame-multiplexedlayer1 frames to a transmission line (to the core node1104).
• Thelayer1 frames transmitted by theedge node1103 to the transmission line are terminated by thelayer1termination section1700 of the reception section (1600,1601) of thecore node1104.
• Thelayer1termination section1700 establishes byte synchronization and frame synchronization with regard to each input line by use of the “Header CRC16” identifiers of the headers of thelayer1 frames. Thelayer1termination section1700 establishes the frame synchronization by checking the “Header CRC16” identifier. If the result of the check is “0”, thelayer1termination section1700 judges that the frame synchronization has been established.
• Thelayer1termination section1700 refers to the “Packet Length” identifier in thelayer1 frame header in order to establish frame synchronization with the next frame, thereby the reference of the “Header CRC16” identifier contained in thenext layer1 frame header is enabled.
• Subsequently, thelayer1termination section1700 refers to the “Protocol” identifier in thelayer1 frame header and thereby judges the type (STM, ATM, IP) of thelayer2 frame contained in the payload of thelayer1 frame.
• Layer1 frames that are judged by thelayer1termination section1700 asSTM layer1 frames are sent to theSTM layer2termination section1701. TheSTM layer2termination section1701 which received theSTM layer1 frames extractsSTM layer2 frames from theSTM layer1 frames.
• The priority processing scheduler1705 checks whether or not anSTM layer2 frame exists in theSTM layer2termination section1701. Incidentally, the “Priority” identifiers of theSTM layer1 frames have been set higher in comparison withlayer1 frames of other types.
• Therefore, when anSTM layer2 frame exists in theSTM layer2termination section1701, the priority processing scheduler1705 instructs theSTM layer2termination section1701 to output theSTM layer2 frames to theframe multiplexing section1704.
• According to the instructions of the priority processing scheduler1705, theSTM layer2termination section1701 outputs theSTM layer2 frames to theframe multiplexing section1704. Theframe multiplexing section1704 frame multiplexes theSTM layer2 frames from theSTM layer2termination section1701 withATM layer2 frames supplied from theATM layer2termination section1702 andIP layer2 frames supplied from theIP layer2termination section1703, and sends the frame-multiplexedlayer2 frames to thelayer2frame switch1602.
• Thelayer2frame switch1602 transmits thelayer2 frames to appropriate output lines (transmission section1603 or1604) based on the label information contained in thelayer2 frame headers.
• In the transmission section (1603,1604) of thecore node1104, theframe separation section1804 judges the protocol type (STM, ATM, IP) of eachlayer2 frame supplied from thelayer2frame switch1602 based on control information which is transferred in thecore node1104.Layer2 frames that are judged by theframe separation section1804 asSTM layer2 frames are sent to theSTM layer1frame generation section1801.
• Thetransmission scheduler1805 checks whether or not anSTM layer2 frame exists in theSTM layer1frame generation section1801. If anSTM layer2 frame exists in theSTM layer1frame generation section1801, thetransmission scheduler1805 instructs theSTM layer1frame generation section1801 tooutput STM layer1 frames to theframe multiplexing section1800 periodically (125 μsec). Incidentally, the transfer of theSTM layer1 frames is conducted with higher priority thanlayer1 frames of other types.
• According to the instructions of thetransmission scheduler1805, theSTM layer1frame generation section1801 converts the storedSTM layer2 frames intoSTM layer1 frames and outputs theSTM layer1 frames to theframe multiplexing section1800 periodically (125 μsec). Theframe multiplexing section1800 frame multiplexes theSTM layer1 frames from theSTM layer1frame generation section1801 withATM layer1 frames supplied from theATM layer1frame generation section1802 andIP layer1 frames supplied from theIP layer1 frame generation section1803, and transmits the frame-multiplexedlayer1 frames to a transmission line (to the core node1105).
• Thereafter, theSTM layer1 frames are transferred to theedge node1110 shown inFIG. 12 via thecore nodes1105 and1109.
• Theedge node1110 receives thelayer1 frames from thecore node1109. In the reception section of theedge node1110, theframe separation section1509 establishes bit synchronization, byte synchronization and frame synchronization by use of the headers of thelayer1 frames.
• After the establishment of the frame synchronization, theframe separation section1509 refers to the “Protocol” identifier of thelayer1 frame and thereby judges whether the data contained in the payload of thelayer1 frame is anSTM layer2 frame, anATM layer2 frame or anIP layer2 frame.
• Theframe separation section1509 also refers to the “Packet Length” identifier of thelayer1 frame header and thereby grasps the total length and the rear end of thelayer1 frame payload. In the case where the data contained in thelayer1 frame payload is anSTM layer2 frame, theframe separation section1509 sends thelayer1 frame to theframe termination section1508.
• Theframe termination section1508 extracts STM signals from theSTM layer1 frame and sends the STM signals to the STMsignal transmission section1505. The STM signals are transferred by the STMsignal transmission section1505 to the STM device1111 (1502).
• As explained above, theSTM layer1 frames containing the STM signals are transferred to the destination at precisely fixed intervals (125 μsec) maintaining the end-to-end circuit quality monitoring functions (end-to-end performance monitoring functions).
• Next, the transfer of ATM cells in the data transfer system ofFIG. 12 will be explained in detail.
• Referring toFIG. 15, in the transmission section of theedge node1103, the ATMcell reception section1404 receives ATM cells from the ATM device1101 (1401). The ATMcell reception section1404 terminates thelayer1 which is used between the ATM device1101 (1401) and theedge node1103, establishes ATM cell synchronization, and sends the ATM cells to theATM layer1frame generation section1409.
• TheATM layer1frame generation section1409 collects ATM cells corresponding to the same VP (Virtual Path) and thereby constructsATM layer2 frames which are shown inFIG. 4A. As shown inFIG. 4A, theATM layer2 frame contains a plurality of ATM cells. TheATM layer1frame generation section1409 generates anATM layer2 frame header (containing a route label) and adds theATM layer2 frame header to theATM layer2 frame payload.
• TheATM layer1frame generation section1409 generates alayer1 frame header including the “Packet Length” identifier (indicating the length of theATM layer1 frame payload), the “Priority” identifier (indicating the type (CBR, UBR, etc.) of ATM), the “Protocol” identifier (indicating ATM), the “Frame Mode” identifier (indicating “Single Frame”) and the “Stuff” identifier (indicating “No Stuffing”), and adds thelayer1 frame header to thelayer2 frame. Incidentally, in theATM layer1 frames, the “Frame Mode” identifier is always set to “00” (Single Frame) and the “Stuff” identifier is always set to “0” (No Stuffing) (seeFIGS. 5B and 5C).
• TheATM layer1frame generation section1409 conducts the CRC16 operation to theATM layer1 frame header and adds the result to the bottom of theATM layer1 frame header. Further, theATM layer1frame generation section1409 conducts the CRC16 or CRC32 to theATM layer1 frame payload and adds the result to the rear end of theATM layer1 frame.
• After the transfer of theSTM layer1 frame from theSTM layer1frame generation section1410 to theframe multiplexing section1414, thescheduler section1413 instructs theATM layer1frame generation section1409 to output theATM layer1 frames to theframe multiplexing section1414. According to the instruction, theATM layer1frame generation section1409 outputs theATM layer1 frames to theframe multiplexing section1414.
• Theframe multiplexing section1414 frame multiplexes theATM layer1 frames from theATM layer1frame generation section1409 withSTM layer1 frames supplied from theSTM layer1frame generation section1410 andIP layer1 frames supplied from theIP layer1frame generation section1412, and transmits the frame-multiplexedlayer1 frames to the transmission line (to the core node1104).
• In the reception section (1600,1601) of thecore node1104, thelayer1termination section1700 receives the frame-multiplexedlayer1 frames and establishes byte synchronization and frame synchronization with regard to each input line by checking the “Header CRC16” identifier of eachlayer1 frame header.
• Thelayer1termination section1700 refers to the “Protocol” identifiers of the headers of thelayer1 frames, thereby extractsATM layer1 frames, and sends theATM layer1 frames to theATM layer2termination section1702. TheATM layer2termination section1702 which received theATM layer1 frame extracts theATM layer2 frame from theATM layer1 frame.
• According to the instruction of the priority processing scheduler1705, theATM layer2 frame stored in theATM layer2termination section1702 is outputted to theframe multiplexing section1704 after the transfer of anSTM layer2 frame from theSTM layer2termination section1701 to theframe multiplexing section1704.
• Theframe multiplexing section1704 frame multiplexes theATM layer2 frames from theATM layer2termination section1702 withSTM layer2 frames supplied from theSTM layer2termination section1701 andIP layer2 frames supplied from theIP layer2termination section1703, and sends the frame-multiplexedlayer2 frames to thelayer2frame switch1602 of thecore node1104.
• Thelayer2frame switch1602 outputs thelayer2 frames to appropriate lines (transmission section1603 or1604) based on the label information which is contained in thelayer2 frame headers.
• In the transmission section (1603,1604) of thecore node1104, theframe separation section1804 separates the frame-multiplexedlayer2 frames depending on their protocols (by use of the aforementioned control information), extractsATM layer2 frames, and sends theATM layer2 frames to theATM layer1frame generation section1802.
• TheATM layer1frame generation section1802 generatesATM layer1 frames by use of theATM layer2 frames supplied from theframe separation section1804 and the aforementioned control information.
• Thetransmission scheduler1805 instructs theATM layer1frame generation section1802 to output theATM layer1 frame to theframe multiplexing section1800 after each of the periodical instructions (125 μL sec) to theSTM layer1frame generation section1801 tooutput STM layer1 frames to theframe multiplexing section1800.
• According to the instructions of thetransmission scheduler1805, theATM layer1frame generation section1802 outputs the generatedSTM layer1 frame to theframe multiplexing section1800. Theframe multiplexing section1800 frame multiplexes theATM layer1 frames from theATM layer1frame generation section1802 withSTM layer1 frames supplied from theSTM layer1frame generation section1801 andIP layer1 frames supplied from theIP layer1 frame generation section1803, and transmits the frame-multiplexedlayer1 frames to a transmission line (to the core node1105).
• Thereafter, theATM layer1 frames are transferred to theedge node1110 shown inFIG. 12 via thecore nodes1105 and1109.
• In the reception section of theedge node1110, theframe separation section1509 establishes bit synchronization, byte synchronization and frame synchronization by use of the headers of thelayer1 frames.
• After the establishment of the frame synchronization, theframe separation section1509 refers to the “Protocol” identifier of thelayer1 frame and thereby judges whether or not thelayer1 frame is anATM layer1 frame.
• Theframe separation section1509 also refers to the “Packet Length” identifier of thelayer1 frame header and thereby grasps the total length and the rear end of thelayer1 frame payload. In the case where thelayer1 frame is anATM layer1 frame, theframe separation section1509 sends theATM layer1 frame to theframe termination section1507.
• Theframe termination section1508 extracts anATM layer2 frame from theATM layer1 frame, extracts ATM cells from theATM layer2 frame, and sends the ATM cells to the ATMcell transmission section1504. The ATM cells are transferred by the ATMcell transmission section1504 to the ATM device1112 (1501).
• As explained above, the ATM cells can be transferred together with data of different protocols (STM signals, IP packets) by use of a common frame format, therefore, different types of data can be handled and transferred in a network concurrently and with a common method.
• Therefore, the STM networks, the ATM networks and the IP networks which have been constructed separately and independently can be integrated or constructed as a common integrated network.
• Next, the transfer of IP packets in the data transfer system ofFIG. 12 will be explained in detail.
• Referring toFIG. 15, in the transmission section of theedge node1103, the IPpacket reception section1403 receives IP packets (IP packet data) from the IP router1102 (1400). The IPpacket reception section1403 terminates thelayer1 and thelayer2 which are used between the IP router1102 (1400) and theedge node1103, thereby extracts IP packets, and stores the IP packets in theIP layer2frame generation section1408.
• The routelabel generation section1406 generates a route label based on the IP layer information (destination IP address, source IP address, “Protocol Identification”) contained in the IP packet header. Depending on cases, header information of upper protocols (TCP (Transport Control Protocol), UDP (User Datagram Protocol)) at the front end of the IP packet payload is referred to for the generation of the route label.
• The routelabel generation section1406 sends the generated route label to theIP layer2frame generation section1408.
• The flowlabel generation section1407 generates a flow label based on the header information of the IP packet. The flow label is a field which is referred to in the network for conducting flow distribution to two or more OCHs which are forming a link.
• The flow labels have to be provided to theIP layer2 frames so that the same IP flows (that is, IP flows having the same destination IP address and the same source IP address, or IP flows having the same destination IP address and the same source IP address and the same parameter in the IP header information) will have the same flow labels.
• The flow label is calculated uniquely from the IP header information etc, however, it is preferable that the flow labels take random (as random as possible) values that are determined depending on the IP header information. For example, the flow label can be calculated by the flowlabel generation section1407 by conducting the Hash operation to the IP layer information (the IP packet header). The flowlabel generation section1407 sends the generated flow label to theIP layer2frame generation section1408.
• TheIP layer2frame generation section1408 generates anIP layer2 frame by packing the IP packet in theIP layer2 frame payload and packs the route label and the flow label in theIP layer2 frame header. TheIP layer2 frames generated by theIP layer2frame generation section1408 are stored in theIP layer1frame generation section1412.
• Thescheduler section1413 instructs theIP layer1frame generation section1412 to output anIP layer1 frame to theframe multiplexing section1414 if theIP layer1frame generation section1412 is storing anIP layer1 frame. Thescheduler section1413 gives the above instruction after instructing theATM layer1frame generation section1409 to output anATM layer1 frame to theframe multiplexing section1414. According to the instructions of thescheduler section1413, theIP layer1frame generation section1412 outputs aprimary IP layer1 frame to theframe multiplexing section1414, giving higher priority than besteffort IP layer1 frames.
• As mentioned before, a besteffort IP layer1 frame has to be transferred in a remaining space (best effort IP transfer space) between theSTM layer1 frame, theATM layer1 frames and theprimary IP layer1 frames in the 125 μsec transfer space, as shown inFIGS. 10 and 11.
• Therefore, when thescheduler section1413 instructs theIP layer1frame generation section1412 to output a besteffort IP layer1 frame, thescheduler section1413 informs theIP layer1frame generation section1412 about the best effort IP transfer space length L (byte).
• Based on the best effort IP transfer space length L, theIP layer1frame generation section1412 determines the length etc. of a besteffort IP layer1 frame to be outputted to theframe multiplexing section1414, as shown in the flow chart ofFIG. 21. Incidentally, inFIG. 21, the explanation is given ignoring the “Payload CRC” field, for the sake of simplicity. In the case where the “Payload CRC” field is employed, the “Payload CRC” field is added to eachIP layer1 frame when theIP layer1 frame is generated and transferred as a single frame, a BOM frame, a COM frame or an EOM frame, and the length of the “Payload CRC” field is taken into consideration in the calculations in the flow chart ofFIG. 21.
• When theIP layer1frame generation section1412 received the instruction (to output a besteffort IP layer1 frame to the frame multiplexing section1414) and a length parameter (indicating the best effort IP transfer space length L), theIP layer1frame generation section1412 first judges whether or not there is an EOM frame remaining therein (step S2200). If a remaining EOM frame exists (“Yes” in the step S2200), theIP layer1frame generation section1412 compares the length M of the EOM frame with the best effort IP transfer space length L (step S2201).
• If the EOM frame length M is longer than the best effort IP transfer space length L (“M>L” in the step S2201), theIP layer1frame generation section1412 partitions the EOM frame and extracts the first segment of the EOM frame. The length of the extracted first segment (including a header) is set to L.
• TheIP layer1frame generation section1412 outputs the extracted first segment of the EOM frame to theframe multiplexing section1414 as a COM frame. The remaining segment of the EOM frame is stored in theIP layer1frame generation section1412 as an EOM frame (having alayer1 frame header) (step S2202), thereby the process is ended.
• If the EOM frame length M is equal to the best effort IP transfer space length L (“M=L” in the step S2201), theIP layer1frame generation section1412 outputs the EOM frame to theframe multiplexing section1414 without partitioning the EOM frame (step S2203), thereby the process is ended.
• If the EOM frame length M is shorter than the best effort IP transfer space length L (“M<L” in the step S2201), theIP layer1frame generation section1412 compares the best effort IP transfer space length L with the EOM frame length M and the minimal dummy frame length D added together (M+D) (step S2204).
• If the length M+D is equal to the best effort IP transfer space length L (“M+D=L” in the step S2204), theIP layer1frame generation section1412 outputs the EOM frame (length: M bytes) to the frame multiplexing section1414 (step S2207) and thereafter outputs the minimal dummy frame (length: D bytes) to the frame multiplexing section1414 (step S2208), thereby the process is ended.
• If the length M+D is longer than the best effort IP transfer space length L (“M+D>L” in the step S2204), theIP layer1frame generation section1412 inserts the stuff data after the payload of the EOM frame. The length of the stuff data is set to L−M−1 bytes. The 1 byte is used for the “Stuffing Length” identifier which indicates the length of the stuff data. Therefore, in the EOM frame to be transmitted, the “Stuffing Length” identifier (1 byte) is inserted at the top of thelayer1 frame payload and the stuff data (L−M−1 bytes) is inserted at the bottom of thelayer1 frame payload as shown inFIG. 7 (step S2205). Thereafter, theIP layer1frame generation section1412 outputs the EOM frame to the frame multiplexing section1414 (step S2206), thereby the process is ended.
• If the length M+D is shorter than the best effort IP transfer space length L (“M+D<L” in the step S2204), theIP layer1frame generation section1412 outputs the EOM frame to theframe multiplexing section1414 and updates the value of the parameter L (best effort IP transfer space length L) into L−M (L−M→L) (step S2209).
• If no remaining EOM frame exists (“No” in the step S2200) or if the update of the best effort IP transfer space length L has been conducted (step S2209), theIP layer1frame generation section1412 judges whether a besteffort IP layer1 frame to be transferred next exists or not (step S2210).
• If no besteffort IP layer1 frame to be transmitted next exists (“No” in the step S2210), theIP layer1frame generation section1412 outputs a dummy frame of the length L to theframe multiplexing section1414 so as to implement the periodical transmission of theSTM layer1 frames (step S2211), thereby the process is ended.
• If a besteffort IP layer1 frame to be transmitted next exists (“Yes” in the step S2210), theIP layer1frame generation section1412 obtains the length B of the besteffort IP layer1 frame to be transmitted next (step S2212), and compares the besteffort IP layer1 frame length B with the best effort IP transfer space length L (step S2213).
• If the besteffort IP layer1 frame length B is longer than the best effort IP transfer space length L (“B>L” in the step S2213), theIP layer1frame generation section1412 partitions the besteffort IP layer1 frame into a BOM frame of the length L and an EOM frame (step S2214). Thereafter, theIP layer1frame generation section1412 outputs the BOM frame of the length L to theframe multiplexing section1414 and stores the EOM frame (step S2215), thereby the process is ended.
• If the besteffort IP layer1 frame length B is equal to the best effort IP transfer space length L (“B=L” in the step S2213), theIP layer1frame generation section1412 outputs the besteffort IP layer1 frame to theframe multiplexing section1414 as a single frame, without partitioning the besteffort IP layer1 frame (step S2216), thereby the process is ended.
• If the besteffort IP layer1 frame length B is shorter than the best effort IP transfer space length L (“B<L” in the step S2213), theIP layer1frame generation section1412 compares the best effort IP transfer space length L with the besteffort IP layer1 frame length B and the minimal dummy frame length D added together (B+D) (step S2217).
• If the length B+D is equal to the best effort IP transfer space length L (“B+D=L” in the step S2217), theIP layer1frame generation section1412 outputs the besteffort IP layer1 frame (length: B) to theframe multiplexing section1414 as a single frame (step S2219) and thereafter outputs the minimal dummy frame (length: D) to the frame multiplexing section1414 (step S2220), thereby the process is ended.
• If the length B+D is longer than the best effort IP transfer space length L (“B+D>L” in the step S2217), theIP layer1frame generation section1412 inserts the stuff data after the payload of the besteffort IP layer1 frame to be transmitted next. The length of the stuff data is set to L−B−1 bytes. The 1 byte is used for the “Stuffing Length” identifier which indicates the length of the stuff data. Therefore, in the besteffort IP layer1 frame to be transmitted next, the “Stuffing Length” identifier (1 byte) is inserted at the top of thelayer1 frame payload and the stuff data (L−B−1 bytes) is inserted at the bottom of thelayer1 frame payload as shown inFIG. 7 (step S2221). Thereafter, theIP layer1frame generation section1412 outputs the besteffort IP layer1 frame to the frame multiplexing section1414 (step S2222), thereby the process is ended.
• If the length B+D is shorter than the best effort IP transfer space length L (“B+D<L” in the step S2217), theIP layer1frame generation section1412 outputs the besteffort IP layer1 frame to theframe multiplexing section1414 as a single frame and updates the value of the parameter L (best effort IP transfer space length L) into L−B (L−B→L) (step S2218). Thereafter, theIP layer1frame generation section1412 returns to the step S2212.
• By the algorithm which has been described above, the best effort IP transfer space of the length L is precisely filled and thereby the periodical transmission of theSTM layer1 frames (interval: 125 μsec) is implemented successfully.
• Theframe multiplexing section1414 frame multiplexes theIP layer1 frames (theprimary IP layer1 frames and the besteffort IP layer1 frames) from theIP layer1frame generation section1412 withSTM layer1 frames supplied from theSTM layer1frame generation section1410 andATM layer1 frames supplied from theATM layer1frame generation section1409, and transmits the frame-multiplexedlayer1 frames to the transmission line (to the core node1104).
• In the reception section (1600,1601) of thecore node1104, thelayer1termination section1700 receives the frame-multiplexedlayer1 frames and establishes byte synchronization and frame synchronization with regard to each input line by checking the “Header CRC16” identifier of eachlayer1 frame header.
• Thelayer1termination section1700 refers to the “Protocol” identifiers of the headers of thelayer1 frames, thereby extractsIP layer1 frames, and sends theIP layer1 frames to theIP layer2termination section1703.
• TheIP layer2termination section1703 extracts anIP layer2 frame from the payload of theIP layer1 frame supplied from thelayer1termination section1700 if theIP layer1 frame is a single frame.
• If theIP layer1 frame supplied from thelayer1termination section1700 is a BOM frame, theIP layer2termination section1703 waits for the arrival of COM frames and an EOM frame, and thereafter reconstructs anIP layer2 frame by connecting the payloads of the BOM frame, the COM frames and the EOM frame.
• If the stuff data has been contained in theIP layer1 frame, theIP layer2termination section1703 removes the stuff data from theIP layer1 frame.
• The priority processing scheduler1705, after giving the instructions to theSTM layer2termination section1701 and theATM layer2termination section1702, instructs theIP layer2termination section1703 to output one or moreprimary IP layer2 frames stored therein to theframe multiplexing section1704. Thereafter, the priority processing scheduler1705 instructs theIP layer2termination section1703 to output one or more besteffort IP layer2 frames stored therein to theframe multiplexing section1704.
• According to the instructions of the priority processing scheduler1705, theIP layer2termination section1703 outputs theprimary IP layer2 frames and the besteffort IP layer2 frames to theframe multiplexing section1704.
• Theframe multiplexing section1704 frame multiplexes theIP layer2 frames (theprimary IP layer2 frames and the besteffort IP layer2 frames) withSTM layer2 frames supplied from theSTM layer2termination section1701 andATM layer2 frames supplied from theATM layer2termination section1702, and sends the frame-multiplexedlayer2 frames to thelayer2frame switch1602 of thecore node1104.
• Thelayer2frame switch1602 transmits thelayer2 frames to appropriate output lines (transmission section1603 or1604) based on the label information contained in thelayer2 frame headers.
• In the transmission section (1603,1604) of thecore node1104, theframe separation section1804 separates the frame-multiplexedlayer2 frames depending on their protocols (based on the control information transferred in the core node1104), extractsIP layer2 frames, and sends theIP layer2 frames to theIP layer1 frame generation section1803.
• According to the instructions of thetransmission scheduler1805, theIP layer1 frame generation section1803 converts theIP layer2 frames intoIP layer1 frames and outputs theIP layer1 frames to theframe multiplexing section1800. The conversion from theIP layer2 frames into theIP layer1 frames is conducted in the same way as the conversion which is conducted in theedge node1103.
• Theframe multiplexing section1800 frame multiplexes theIP layer1 frames from theIP layer1 frame generation section1803 withSTM layer1 frames supplied from theSTM layer1frame generation section1801 andATM layer1 frames supplied from theATM layer1frame generation section1802, and transmits the frame-multiplexedlayer1 frames to a transmission line (to the core node1105).
• FIGS. 13 and 14 are schematic diagrams showing the transfer of theIP layer1 frames in a network by use of the route label and the flow label.
• The route label which is contained in thelayer2 frame header of anIP layer1 frame is used for determining relaying nodes (core nodes) for transferring thelayer1 frame. In the example ofFIG. 13, theIP layer1 frame is transferred from an edge node (EN)1200 to an edge node (EN)1207 via core nodes (CN)1201,1202 and1204. The core node (CN)1201 refers to the route label contained in theIP layer1 frame and outputs theIP layer1 frame to an output line (output port) corresponding to the route label, thereby theIP layer1 frame is transferred to the core node (CN)1202. Thereafter, switching is executed similarly by the core nodes (CN)1202 and1204, and thereby theIP layer1 frame is transferred to the edge node (EN)1207.
• Each link between two core nodes is composed of two or more wavelengths (optical channels), however, the route label does not designate the wavelength for being used. The route label is only used for the determination of the transfer route of theIP layer1 frame (the sequence of relaying nodes).
• The flow label which is contained in thelayer2 frame header of anIP layer1 frame designates a wavelength to be used for transferring theIP layer1 frame when a link is composed of two or more wavelengths. The wavelength to be used for transferring anIP layer1 frame is determined by each core node (CN) for eachIP layer2 frame (for eachIP layer1 frame), by referring to the flow label contained in theIP layer1 frame as shown inFIG. 14. In the case ofFIG. 14, the core node (CN)1301 selects a wavelength from two or more wavelengths forming the link between the core nodes (CN)1301 and1302 by referring to the flow label of theIP layer1 frame, and transmits theIP layer1 frame to the core node (CN)1302 by use of the selected wavelength. Incidentally, in a core node (CN),IP layer2 frames having the same flow labels are transmitted by use of the same wavelength.
• Referring again to the data transfer system ofFIG. 12, in the reception section of theedge node1110, theframe separation section1509 receives frame-multiplexedlayer1 frames and establishes bit synchronization, byte synchronization and frame synchronization by referring to thelayer1 frame headers.
• Theframe separation section1509 refers to the “Protocol” identifiers of thelayer1 frame headers, thereby extractsIP layer1 frames from the frame-multiplexedlayer1 frames, and sends theIP layer1 frames to theframe termination section1506.
• Theframe termination section1506 extracts anIP layer2 frame from the payload of theIP layer1 frame supplied from theframe separation section1509 if theIP layer1 frame is a single frame.
• If theIP layer1 frame supplied from theframe separation section1509 is a BOM frame, theframe termination section1506 waits for the arrival of COM frames and an EOM frame, and thereafter reconstructs anIP layer2 frame by connecting the payloads of the BOM frame, the COM frames and the EOM frame.
• If the stuff data has been contained in theIP layer1 frame, theframe termination section1506 removes the stuff data from theIP layer1 frame.
• Theframe termination section1506 extracts an IP packet from theIP layer2 frame and sends the IP packet to the IPpacket transmission section1503. The IPpacket transmission section1503 transmits the IP packet to the IP router1113 (1500).
• As described above, in the operation of the data transfer system in accordance with the embodiment of the present invention, theSTM layer1 frames are transferred at fixed periods (125 μsec). Bit synchronization is established in the physical layer, and byte synchronization and frame synchronization are established by use of the “Header CRC16” identifier, thereby the STM signals are necessarily transferred at fixed intervals (125 μsec) maintaining the end-to-end circuit quality monitoring functions (end-to-end performance monitoring functions).
• The STM signals, the ATM cells and the IP packets are transferred by use of a common frame format, therefore, the different types of information can be handled and managed in a network concurrently by a common method.
• Therefore, the STM networks, the ATM networks and the IP networks which have been constructed separately and independently can be integrated or constructed as a common or integrated network.
• By the definition of the route label and the flow label as transfer information for theIP layer2 frames, IP packets can be transferred appropriately by simple procedures even when each link is composed of two or more wavelengths by means of WDM (Wavelength Division Multiplexing).
• When the above embodiment is applied to an IP network (without STM and ATM), theprimary IP layer1 frames can be transferred at fixed intervals (125 μl sec, for example), and thereby the transfer of theprimary IP layer1 frames can be conducted with the same high quality (without delay variation) as theSTM layer1 frames of the above embodiment.
• As set forth hereinabove, by the frame construction method, the frame construction device and the data transfer system in accordance with the present invention, different types of data (STM signals, ATM cells and IP packets) can be transferred in a network by use of a common frame format.
• Thelayer1 frames, containing the STM signals, the ATM cells and the IP packets addressed to different destinations, can be transferred to their destinations appropriately.
• STM networks, ATM networks and IP networks which have been constructed separately and independently can be integrated or constructed as a common or integrated network.
• Bit errors which can occur during the transfer of thelayer1 frames can be detected by each node by use of the “Payload CRC” field, thereby the link monitoring can be executed by each node. By use of the OAM frames, path monitoring with regard to a path from the ingress point to the egress point can be conducted by a node at the egress point by reference to the OAM frame.
• Thelayer2 frames and thelayer1 frames in accordance with the present invention can be constructed regardless of the size of the STM signal, the ATM cell or the IP packet which is packed in thelayer2 frame payload. Therefore, thelayer1 frame is constructed even if the size of data (STM signal, ATM cell or IP packet) to be transferred is very small. On the other hand, even when the amount of best effort IP packets to be transferred is very large, by the priority processing of the above embodiment in order of STM, ATM, primary IP and best effort IP, theSTM layer1 frames and theATM layer1 frames (and theprimary IP layer1 frames) can be transferred without being affected by the congestion in the best effort IP traffic.
• Thelayer1 frames in accordance with the present invention are frame multiplexed and transferred with predetermined periodicity (125 μsec, for example), thereby the bit synchronization in the physical layer can be established. By use of the “Header CRC16” identifiers of thelayer1 frame headers, the byte synchronization and the frame synchronization are established.
• The type of data which is contained and transferred in thelayer1 frame can be detected by the reference to the “Protocol” identifier of thelayer1 frame header.
• The priority (in data transfer) of the data contained and transferred in thelayer1 frame can be detected by the reference to the “Priority” identifier of thelayer1 frame header, thereby theSTM layer1 frames (CBR traffic) are transferred with the highest priority.
• The length of thelayer1 frame header is fixed (6 bytes in the embodiment), thereby the reference to the header information (identifiers) can be conducted by each node easily and correctly.
• In the case where the stuff data has been stuffed in thelayer1 frame payload in order to adjust the length of thelayer1 frame in the frame transfer, a node which received thelayer1 frame can easily remove the stuff data by the reference to the “Stuff” identifier and the “Stuffing Length” identifier.
• Thelayer1 frame in accordance with the present invention can accommodate and transfer the N-channel trunk signal of N×64 Kbps which has been transferred between conventional switches, therefore, the conventional telephone networks (voice transmission telecommunication networks) can be accommodated in the data transfer system of the present invention.
• TheSTM layer1 frames of the present invention can be transferred at precisely fixed intervals (125 μsec in the above embodiment) by the adjustment of the length of the besteffort IP layer1 frame. The adjustment of the besteffort IP layer1 frame length is conducted by the partitioning of the besteffort IP layer1 frame, the insertion of the stuff data etc. as explained referring toFIG. 21. Even when there is no besteffort IP layer1 frame to be transferred, the periodical transfer of theSTM layer1 frames (125 μsec) is maintained by the transfer of the dummy frames.
• In the above embodiment, the transfer of the STM signals (contained in theSTM layer1 frames) can be executed with higher priority than the ATM signals (contained in theATM layer1 frames) and the IP packets (contained in theIP layer1 frames), and the transfer of the ATM signals can be conducted with higher priority than the IP packets.
• When the present invention is applied to an IP network (without STM and ATM), theprimary IP layer1 frames can be transferred at fixed intervals (125 μsec, for example), thereby the transfer of the primary IP packets can be conducted with the same high quality (without delay variation) as the conventional STM signals.
• The best effort IP packets, which is of lower priority in the IP packets, are transferred with the lowest priority in the embodiment, thereby the STM signals, the ATM cells and the primary IP packets, which should be handled as high priority traffic, can be transferred with higher priority.
• A core node which relays thelayer1 frames can judge the type (protocol) of data which is contained in thelayer1 frame by the reference to the “Protocol” identifier of thelayer1 frame header, thereby the core node is enabled to judge the priority of transfer of thelayer1 frame.
• The core node which relays thelayer1 frames can transfer the STM signals (STM layer1 frames) with the highest priority among the various types of data at precisely fixed intervals (125 μsec) so as to implement the end-to-end performance monitoring functions.
• The core node which relays thelayer1 frames can determine the next node (output port) for transferring thelayer1 frame by the reference to the route label of thelayer2 frame header.
• The core node which relays thelayer1 frames can select the wavelength for the transfer of thelayer1 frame by the reference to the flow label of thelayer2 frame header.
• Incidentally, while the processes of the flow chart ofFIG. 21 for the transfer of the besteffort IP layer1 frames were explained as processes on the level oflayer1 frames, it is also possible to let the edge nodes and core nodes conduct equivalent processes (partitioning, stuffing, etc.) on the level oflayer2 frames or IP packets.
• The priority processing which was employed in the above embodiment is only an example and other algorithms can also be employed for the priority processing. For instance, while the transfer of aprimary IP layer1 frame in the fixed cycle (125 μsec) was executed after the transfer of all theATM layer1 frames stored in the node in the above embodiment, the transfer of theprimary IP layer1 frame can also be executed after the transfer of oneATM layer1 frame. In the same way, while the transfer of a besteffort IP layer1 frame in the fixed cycle (125 μsec) was started after the transfer of all theprimary IP layer1 frames stored in the node, the transfer of the besteffort IP layer1 frame can also be started after the transfer of oneprimary IP layer1 frame. The length of the fixed cycle (125 μsec) employed in the above embodiment can be changed depending on design requirements of the data transfer system.
• While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by those embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.

Claims (20)

What is claimed is:

1. A method comprising:

appending, by a network device, a first layer1 frame header to a first payload to form a first layer1 frame,

the first payload including first layer2 data of multi-protocol layer2 data received from a plurality of network devices, and

the first layer1 frame header including a first protocol identifier indicating that the first layer2 data is associated with a first protocol;

appending, by the network device, a second layer1 frame header to a second payload to form a second layer1 frame,

the second payload including second layer2 data of the multi-protocol layer2 data,

the second layer1 frame header including a second protocol identifier indicating that the second layer2 data is associated with a second protocol that is different than the first protocol, and

a length of the first layer1 frame being different from a length of the second layer1 frame; and

outputting, from the network device, the first layer1 frame and the second layer1 frame in a same format to a network.

2. The method ofclaim 1, where the first protocol and the second protocol each comprise one of:

synchronous transfer mode (STM),

asynchronous transfer mode (ATM),

Internet protocol (IP), or

multiprotocol label switching (MPLS).

3. The method ofclaim 1, where outputting the first layer1 frame and the second layer1 frame includes:

outputting the first layer1 frame and the second layer1 frame to a single frame-type network.

4. The method ofclaim 1, further comprising:

constructing the first layer1 frame header to include a first cyclic redundancy check (CRC) identifier indicating a first CRC result performed on portions of the first layer1 frame header; and

constructing the second layer1 frame header to include a second CRC identifier indicating a second CRC result performed on portions of the second layer1 frame header,

the first CRC result and the second CRC result enabling a node in the network to conduct bit synchronization, byte synchronization, or frame synchronization for the first layer1 frame and the second layer1 frame, respectively.

5. The method ofclaim 1, further comprising:

constructing the first layer1 frame header to include a first cyclic redundancy check (CRC) identifier indicating a first CRC result performed on portions of the first layer1 frame header; and

constructing the second layer1 frame header to include a second CRC identifier indicating a second CRC result performed on portions of the second layer1 frame header,

the first layer1 frame header further including a payload CRC identifier indicating a result of a CRC operation for the first payload, and

the payload CRC identifier enabling a node in the network to conduct payload data quality monitoring.

6. The method ofclaim 1, where the first protocol comprises Synchronous Transfer Mode (STM) and the second protocol comprises multiprotocol label switching, the method further comprising:

packing a layer2 header and a plurality of STM signals, addressed to a same destination, into the first payload.

7. The method ofclaim 1, where the first protocol comprises Internet Protocol (IP) and the second protocol comprises multiprotocol label switching, the method further comprising:

packing a layer2 header and an IP packet into the first payload,

the layer2 header including a route label as information for routing the first layer1 frame through the network and a flow label as information for selecting a particular optical channel, of a plurality of optical channels, for transferring the first layer1 frame through the network.

8. A device comprising:

one or more processors to:

append a first layer1 frame header to a first payload to form a first layer1 frame,

the first payload including first layer2 data of multi-protocol layer2 data received from a plurality of network devices, and

the first layer1 frame header including a first protocol identifier indicating that the first layer2 data is associated with a first protocol;

append a second layer1 frame header to a second payload to form a second layer1 frame,

the second payload including second layer2 data of the multi-protocol layer2 data,

the second layer1 frame header including a second protocol identifier indicating that the second layer2 data is associated with a second protocol that is different from the first protocol, and

a length of the first layer1 frame being different from a length of the second layer1 frame; and

output the first layer1 frame and the second layer1 frame in a same format to a network.

9. The device ofclaim 8, where the first protocol and the second protocol each comprise one of:

synchronous transfer mode (STM),

asynchronous transfer mode (ATM),

Internet protocol (IP), or

multiprotocol label switching (MPLS).

10. The device ofclaim 8, where, when outputting the first layer1 frame and the second layer1 frame, the one or more processors are to:

output the first layer1 frame and the second layer1 frame to a single frame-type network.

11. The device ofclaim 8, where the one or more processors are further to:

construct the first layer1 frame header to include a first cyclic redundancy check (CRC) identifier indicating a first CRC result performed on portions of the first layer1 frame header; and

construct the second layer1 frame header to include a second CRC identifier indicating a second CRC result performed on portions of the second layer1 frame header,

the first CRC result and the second CRC result enabling a node in the network to conduct bit synchronization, byte synchronization, or frame synchronization for the first layer1 frame and the second layer1 frame, respectively.

12. The device ofclaim 8, where the one or more processors are further to:

construct the first layer1 frame header to include a first cyclic redundancy check (CRC) identifier indicating a first CRC result performed on portions of the first layer1 frame header; and

construct the second layer1 frame header to include a second CRC identifier indicating a second CRC result performed on portions of the second layer1 frame header,

the first layer1 frame header further including a payload CRC identifier indicating a result of a CRC operation for the first payload, and

the payload CRC identifier enabling a node in the network to conduct payload data quality monitoring.

13. The device ofclaim 8, where the first protocol comprises best effort Internet Protocol (IP), and

where the one or more processors are further to:

pack a segment of a partitioned, best effort IP packet, into the first payload, and

construct the first layer1 frame header to include a frame mode identifier classifying the segment as a front end segment, a rear end segment, or neither a front end segment nor a rear end segment.

14. The device ofclaim 13, where the one or more processors construct the first layer1 frame header to include the frame mode identifier classifying the segment as a front end segment, and

where the one or more processors are further to:

pack a layer2 header into the first payload,

the layer2 header including a route label as information for routing the first layer1 frame through the network and a flow label as information for selecting a particular optical channel, of a plurality of optical channels, for transferring the first layer1 frame through the network.

15. A non-transitory computer-readable medium storing instructions, the instructions comprising:

one or more instructions which, when executed by one or more processors, cause the one or more processors to:

append a first layer1 frame header to a first payload to form a first layer1 frame,

the first payload including first layer2 data of multi-protocol layer2 data received from a plurality of network devices, and

the first layer1 frame header including a first protocol identifier indicating that the first layer2 data is associated with a first protocol;

append a second layer1 frame header to a second payload to form a second layer1 frame,

the second payload including second layer2 data of the multi-protocol layer2 data,

the second layer1 frame header including a second protocol identifier indicating that the second layer2 data is associated with a second protocol that is different from the first protocol, and

a length of the first layer1 frame being different from a length of the second layer1 frame; and

output the first layer1 frame and the second layer1 frame in a same format to a network.

16. The non-transitory computer-readable medium ofclaim 15, where the one or more instructions to output the first layer1 frame and the second layer1 frame include:

one or more instructions to output the first layer1 frame and the second layer1 frame to a single frame-type network.

17. The non-transitory computer-readable medium ofclaim 15, where the instructions further comprise:

one or more instructions to construct the first layer1 frame header to include a first cyclic redundancy check (CRC) identifier indicating a first CRC result performed on portions of the first layer1 frame header; and

one or more instructions to construct the second layer1 frame header to include a second CRC identifier indicating a second CRC result performed on portions of the second layer1 frame header,

the first CRC result and the second CRC result enabling a node in the network to conduct bit synchronization, byte synchronization, or frame synchronization for the first layer1 frame and the second layer1 frame, respectively.

18. The non-transitory computer-readable medium ofclaim 15, where the instructions further comprise:

one or more instructions to construct the first layer1 frame header to include a first cyclic redundancy check (CRC) identifier indicating a first CRC result performed on portions of the first layer1 frame header; and

one or more instructions to construct the second layer1 frame header to include a second CRC identifier indicating a second CRC result performed on portions of the second layer1 frame header,

the first layer1 frame header further including a payload CRC identifier indicating a result of a CRC operation for the first payload, and

the payload CRC identifier enabling a node in the network to conduct payload data quality monitoring.

19. The non-transitory computer-readable medium ofclaim 15, where the first protocol comprises best effort Internet Protocol (IP), and

where the one or more instructions further comprise:

one or more instructions to pack a segment of a partitioned, best effort IP packet, into the first payload, and

one or more instructions to construct the first layer1 frame header to include a frame mode identifier classifying the segment as a front end segment, a rear end segment, or neither a front end segment nor a rear end segment.

20. The non-transitory computer-readable medium ofclaim 19, where the one or more instructions to construct the first layer1 frame header to include the frame mode identifier include:

one or more instructions to construct the first layer1 frame header to include the frame mode identifier classifying the segment as a front end segment, and

where the instructions further comprise:

one or more instructions to pack a layer2 header into the first payload,

the layer2 header including a route label as information for routing the first layer1 frame through the network and a flow label as information for selecting a particular optical channel, of a plurality of optical channels, for transferring the first layer1 frame through the network.

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