JP2670613B2 - Packet multiplex communication method - Google Patents

Description

The present invention relates to a packet multiplex communication system for realizing an efficient packet transmission network.

[Conventional technology]

FIG. 1 is a block diagram of a general packet multiplex communication system to which the present invention is applied. In the figure, 1 is a relay transmission network, 2 is a subscriber access network, 3 is a local network or home network, 4 is a long distance transmission network, 5 is a regional transmission network, 6 is an SC relay node (Secondary Center), 7 is a PC relay node (Primary Center), 8 is a subscriber exchange (LS)
(Local Swich), 9 is a remote encoding device, 10 is a packet terminal, 11 is a local network, 12 is a network terminating device, a is a source node, and a'is a destination node. The relay transmission network 1 is hierarchized into a long distance transmission network 4 and a regional transmission network 5. The SC relay node 6 belongs to the long distance transmission network 4, and the PC relay node 7 belongs to the regional transmission network 5. The path of the virtual path (Virtual Path) set between the originating node a and the terminating node a ′ of the subscriber exchange 8 (or exchange) sequentially passes through the originating node a and the relay nodes PC ₁ , SC ₂ ,. Reach the receiving node a '. Symbols 9 to 12 are all terminals for the packet or devices in the network.

FIG. 2 is a block diagram of the format of the packet. In the figure, 13 is a header section, 14 is an information section, 15 is an error detection code, 16 is a packet, CI is a call identifier (Identifier), VP
I is the virtual path identifier. The packet 16 includes a header section 13 and an information section 14, and may have a fixed length or a variable length. The header 13 is a call identifier CI and a virtual path identifier VP.
I, and error detection code 15. The call identifier CI includes a subscriber number and the like, and the error detection code 15 includes a service class indication and an error detection code for the header unit 13 and the like.
Information indicating a path is recorded in the virtual path identifier VPI.

Here, as the information indicating the path of the virtual path set between the originating node a and the terminating node a ′ of the subscriber exchange 8, the node numbers PC ₁ , SC ₂ , ... Of the relay nodes of the path through which the packet 16 passes. , And the terminating node a ′. Record this number in the virtual path identifier VPI of the head unit 13,
It can be used for routing. In this case, in each relay node, the next destination node is identified by the node numbers PC ₁ , SC ₂ , ..., Recorded in the virtual path identifier VPI, and the destination node a ′, and the packet is transmitted to the predetermined output route. To do.

A plurality of virtual paths connecting between two subscriber exchanges are set, a virtual path name is given to this, and this is used as instruction information of the virtual path. That is, each virtual path name is recorded as a path identification code in the virtual path identifier VPI. For example, in FIG. ₂ , two kinds of paths of α ₁ and α ₂ are defined as the paths of two vertical paths connecting the source node a and the destination node a ′. The defined information is written in the routing table of each relay node. When the call is transferred, each relay node identifies the next destination node based on the contents of the virtual path identifier VPI, α ₁ and α ₂ , and according to the contents of the routing table, the packet is forwarded to a predetermined destination. Is sent.
That is, when a call from the originating node a to the terminating node a ′ occurs, α ₁ or α _{2 for} each call in the call setup phase.
According to the state of the network at that time or a certain algorithm, and in the communication phase, α is added to the virtual path identifier VPI of the header unit 13 of the packet belonging to the call.
Write ₁ or α ₂ and send to the vertical path. Each of the relay nodes recognizes the virtual path identifier VPI of the transmitted packet, and the packet is transmitted to a predetermined output route according to the contents described in the preset routing table.

[Problems to be solved by the invention]

Two methods have been described as information for instructing the route,
When the method of (1) is used, if the number of relay nodes is increased or the number of relay nodes to be passed is increased, the number of bits required for the virtual path identifier VPI increases, the header becomes longer, and the packet overhead increases. There was a drawback that

When one of the methods is used, the required bit of the virtual path identifier VPI is the number of combinations between the two exchanges which the subscriber exchange 8 should preset, regardless of the hierarchy of the transit network and the number of passing nodes. It depends on the number of paths. For example, if the number of subscribers exchange 8 is n, the minimum path number R of Bachiyarupasu required to connect between any subscriber exchange of the two _{positions, R = n C 2 = n} (n-
1) / 2 increases by the square of n, for example, when n = 10 ³ , R = 4
At 99,500, 19 bits are required to display R. That is, when the above method is applied to a public network with a large n, the number of virtual paths is increased, the number of bits required for the virtual path identifier VPI is increased, the header is lengthened, and the packet overhead is increased. . In addition, there is a drawback that the memory capacity of the routing table 16 of the relay node device 17 that selects the output link from the virtual path identifier VPI at the node becomes large.

An object of the present invention is to reduce the number of required bits of the virtual path identifier VPI, reduce the packet overhead, and reduce the memory capacity of the routing table of the node.

[Means for solving the problem]

In order to eliminate these drawbacks, in a packet multiplex communication network in which a source node, a destination node, and a relay node are connected by a link in order to transfer a packet, a relay node and a link are provided between the source node and the destination node. The virtual path is set, the capacity is secured for each virtual path in the links between the nodes along the route of the virtual path, and the virtual path number is given to each link in which the virtual path between the adjacent nodes is accommodated. The virtual path number is different from the other virtual path numbers of the links between the nodes, and the input link of each virtual path and its virtual path number, the output link of the same virtual path and its virtual path number are corresponded. The routing table recorded by Necessary information is written in the routing table of each relay node through which the originating and terminating nodes and the virtual path pass when the route path is set, and all packets belonging to the virtual path which are transferred on the link of the virtual path are called in the header part ( In addition to a call identifier for identifying a channel), a virtual path identifier area for identifying a virtual path is provided, and the virtual path number of the link is included in this virtual path identifier, and a call (channel) is set up at the originating node. , A means for identifying one or a plurality of virtual paths set between the source node and a destination node to which the call should be connected, and observing the use status of the one or more virtual paths already set. Depending on the usage status of those virtual paths, make sure there is enough space to accommodate the new call to be set up. If there is a virtual path that can be accommodated, the call is accommodated in the virtual path, and if there is no free space, it has a judgment function that refuses to accommodate the call in the virtual path, and if the call can be accommodated in the virtual path In that case, the virtual path identification number of the virtual path is specified in all the packets belonging to the call, the packet is transferred in the network, and when the packet passes through the relay node, the contents of the routing table are read and Rewriting the virtual path number of the virtual path identifier from the virtual path number of the input link to the virtual path number of the corresponding output link to transfer the packet on the route of the virtual path for which the route and capacity are already defined. Characterize. As a result, a packet multiplex communication system was obtained in which the overhead of the vertical path identification in the header of the packet did not increase.

[Action]

In packet multiplex communication of the present invention, a packet transferred through the virtual path is transferred by rewriting the virtual path identifier VPI of the header part 13 of the packet 16 from the input path virtual path number to the output link virtual path number according to the routing table in the relay node. Because
Misconnection does not occur, and a packet multiplex communication system can be realized with a short virtual path identifier.

〔Example〕

First, the virtual path is set in each node, and the routing table 18 of each node is created. First, a virtual path between a source node a and a destination node a'that connects two arbitrary subscriber exchanges is set, and at each node, a certain number N of multiple virtual paths that can be multiplexed on a transmission line is set. In addition, a virtual path number code is given to each link in which a virtual path between adjacent nodes through which the virtual path passes is accommodated, and a routing table 18 recording this is created and prepared. The virtual pass number is different for each virtual pass within the same link.

Next, the operation will be described. FIG. 3 is a block diagram of an embodiment for explaining the present invention, and FIG. 4 is a diagram of the contents of the routing table. In FIG. 3, 17 is a relay node device, 18 is a routing table, and 19 is a transmission path to and from a node. Input link for relay node #
Among the packets 16 arriving at the relay node device 17 from 1, the packet indicated by A as the virtual path number is reconnected to the output link #k by rewriting the virtual path number as B. By repeating this at each relay node, a logical path between the source node a and the destination node a 'is set. That is, once the path is set, the relay node on the way does not perform call control for each call connection for the call accommodated in the path, and the header unit 13 is used when transferring the packet 16. It is possible to identify only the virtual path identifier VPI in the packet and asynchronously multiplex and transmit the packet 16 to the transmission line.

Since such a system is used, the required number of bits of the virtual path identifier VPI is N when the maximum number of virtual paths that can be simultaneously set in one transmission path is N [log ₂ N] ([x]: x The above minimum integer) [bit] will suffice.

In general, when considering a large-scale network such as a public network, the number of subscriber exchanges is very large, and the number of virtual paths connecting arbitrary subscriber exchanges is very large. However, the amount of AC traffic is large between terminals with a short distance, and the AC traffic between terminals exceeding 100 km is negligibly small compared to all AC traffic. That is,
The probability that the path of the long distance subscriber exchange is set is relatively small, that is, the number of paths that are simultaneously set in one transmission line is a value that is sufficiently smaller than the total number of paths between the subscriber exchanges. However, there is no practical problem.

Thus, by setting N to the necessary minimum,
It is possible to reduce the required number of bits of the virtual path identifier VPI and to significantly reduce the required memory amount of the routing table 18 in the node.

In the above embodiment, an example in which the virtual path number is used for the virtual path connecting the subscriber exchanges to each other has been shown. For example, as shown in FIG. 1, the relay transmission networks 4 and 5 are divided into several layers, and at least one of them is used. It is also possible to use the asynchronous packet multiplex communication system of the present invention as a transmission system between nodes in one hierarchy.

〔The invention's effect〕

As described above, in the communication method described in the present invention, the required minimum number of virtual path identifiers VPI can be reduced by setting the minimum necessary virtual path number. As an example, to enable identification of ₁₀₀₀ C ₂ = 5 × 10 ⁵ routes connecting 1000 subscriber exchanges, secure about 10 ³ as the number of virtual paths that are simultaneously multiplexed on one transmission line. Is enough.

By reducing the number of required bits of the virtual path identifier VPI, it becomes possible to significantly reduce the number of required memories of the routing table 18 in the node.

There is an advantage.

[Brief description of the drawings]

FIG. 1 is a block diagram of a conventional packet multiplex communication system, FIG. 2 is a block diagram of a packet format, FIG. 3 is a block diagram of an embodiment for explaining the present invention, and FIG. 4 is the contents of its routing table. FIG. 1 is a relay transmission network, 2 is a subscriber access network, 3 is a local network or home network, 4 is a long distance transmission network, 5 is a regional transmission network, 6 is an SC relay node, 7 is a PC relay node, 8 Is a subscriber exchange, 9 is a remote encoding device, 10 is a packet terminal, 11 is a local network, and 12 is a network.
Is a network terminating device, 13 is a header part, 14 is an information part, 15 is an error detection code, 16 is a packet, 17 is a relay node device, 18 is a routing table, 19 is a transmission line to and from a node, a
Is a source node, a 'is a destination node, #i is an input link, #k is an output link, SC and PC are relay nodes, α ₁ and α ₂
Is a birch path.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Kaneda, 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo, Nippon Telegraph and Telephone Corporation (56) References IEICE Technical Report IN 87-84 Electronic Information and Communication Technical report of IEICE SE 87-138 Technical report of IEICE SE 87-72

Claims (1)

(57) [Claims] 1. A packet multiplex communication network in which a source node, a destination node and a relay node are connected by a link to transfer a packet, and a virtual path between the source node and the destination node via the relay node and the link. Is set, a capacity is secured for each virtual path in the links between nodes along the path of the virtual path, and a virtual path number is given to each link in which the virtual path between adjacent nodes is accommodated. The path number is made different from the other virtual path numbers of the links between the nodes, and the input link of each virtual path and its virtual path number, the output link of the same virtual path and its virtual path number are recorded correspondingly. A routing table is provided in each virtual path relay node to set the virtual path. Sometimes, necessary information is written in the routing table of each relay node through which the originating and terminating nodes and the virtual path pass, and all packets belonging to the virtual path that are transferred on the link of the virtual path have a call (channel) in the header part. In addition to the call identifier to be identified, a virtual path identifier area for identifying a virtual path is provided, the virtual path number of the link is included in this virtual path identifier, and when a call (channel) is set at the originating node, the originating node And a means for recognizing one or a plurality of virtual paths set up between the receiving nodes to which the call should be connected and observing the use status of the one or more virtual paths already set up. A birch with enough room to accommodate a call to be newly set up depending on the usage of the virtual path. If there is a routing pass, the call is accommodated in the virtual path, and if there is no vacancy, it has a judgment function of refusing to accommodate the call in the virtual path. If the call can be accommodated in the virtual path. Specifies the virtual path identification number of the relevant virtual path in all packets belonging to the call, transfers the packet within the network, reads the contents of the routing table when the packet passes through the relay node, and The virtual path number of the path identifier is rewritten from the virtual path number of the input link to the virtual path number of the corresponding output link, and the packet is transferred on the route of the virtual path whose route and capacity are already defined. Packet multiplex communication system.