JPH01225263A - Packet communicating system - Google Patents

Abstract

PURPOSE:To reduce the capacity of a routing table by defining one or the plural number of logical closed paths or routes in a communication network and transmitting a packet from an outgoing node to an incoming node. CONSTITUTION:When the packet is transferred from a node 0 to a node 6, in the node 0, a value 01 is given to show a closed path L1 is used in an area A to show the header constitution of a packet, which is transferred to the node 6, in an (a). Then, a value 011 is given to an area B to show a third node is the incoming node and the packet is sent to a next node 1 of the closed path L1. In the node 1, the value of the area B is subtracted only by 1 and the number of the closed path to be shown by the area A is obtained from a routing table. Then, the packet is transferred to a next node 2. Samely concerning the node 2, the packet is transferred to the node 6. In the node 6, when the value of the area B is subtracted only by 1, the value goes to be 0. Thus, this packet is received as its own node addressing packet.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a packet communication system that reduces the size of a routing table held by a node.

(Prior Art) As a conventional packet communication method, a path (hereinafter referred to as VP: Virtual Path) commonly used by virtual lines belonging to multiple calls is defined between each originating node and a terminating node. An identifier that identifies this route (hereinafter referred to as VPI)
：Virtual Path Identifier) and a call identifier (hereinafter referred to as CI: Ca1) for identifying the call to which the packet belongs at the destination node and sending it to an appropriate terminal.
There is a method in which the node selects the destination of the packet based on the VPI by displaying the Identifier) in the header of the packet as shown in FIG. However, with this method,
Since it is necessary to give different VPIs to all pairs of routes between originating and receiving nodes, the routing table held by the node becomes large, and the memory cost for storing it becomes large. This phenomenon will be explained below.

FIG. 7 is a block diagram of a node in the conventional method.

In this node, input links 20.20", 20"
The packets arriving from the terminal are manually input to the output destination identification section 21.

The output destination identification unit 21 identifies the destination of the packet,
Extract the VPI from the header. Since the VPI itself does not represent the destination of the packet, the extracted VPI is sent to the routing table 23 that shows the correspondence between the vPI and the destination, and the corresponding vP in the routing table is
Identify the destination from the I column. The packet whose destination has been identified is switched by the packet switch 22,
The output light is transferred to the output link 24.24°, 24” or to the terminal.

In this conventional method, the routing table needs to specify the destination for the VPI of every packet arriving from an input link, and its size requires columns equal to the number of vPs to which the packets arriving at the node belong. v to which a packet arriving at a particular node belongs
Examples of P are shown in FIGS. 5(A) and 5(B).

In FIGS. 5(A) and (B), 0, 1, 2. −．
7 is a node, a, b, c, ...-, j is a link, vp
t.

vP2. -, VPI5 is vpt atte, binary code enclosed in parentheses (0001), (0010), -, (
1111) has SO(7)VPI Te. Same figure (7) VP
I, vP2,-, VPI5 is link a.

v to which the packet that arrives at node 1 via b, e belongs
It is P. This includes vP in which node 1 is the destination node, as shown in FIG. 5(A), and vP in which node 1 is the relay node, as shown in FIG. 5(B). The former is no, do 1
Since there is at least one node between the nodes other than VPI, vP2. -, there are at least seven such as vP7. On the other hand, as the latter vP, the fifth
In diagram (B), node 0 to node 2, node 2 to node 0, node 0 to node 3, node 3 to node 0
, node 0 to node 7, node 7 to node 0, node 3 to node 5, node 5 to node 3, and there are vP8, vP9, -, and VPI5. The routing table of node 1 is as follows (7) VPI, vP2. -, Since it is necessary to indicate the destination for VPI5, the configuration has 15 columns as shown in FIG. In this routing table, vP8 (1000), VPIO (1010),
VPI2 (1100) and vP9 (1001), V
Although both PII (1011) and VPI3 (1101) correspond to the same human output link, it is necessary to search separate columns, leading to an increase in the routing table.

(Problems to be Solved by the Invention) An object of the present invention is to provide a packet communication method that reduces the number of routing tables compared to conventional methods and improves the problems of memory cost and hardware amount in nodes.

(Means for Solving the Problems) The present invention has a communication network in which a plurality of nodes are connected by links, and each node selects a link to send the packet based on information shown in the header of the packet. In packet communication systems in which packets are transferred from a source node to a destination node through an appropriate route, one or more logical circuits or paths are defined in the communication network, and packets are routed through these routes. The first feature is that a part of one cycle or road that includes both an originating node and a destination node is transferred as a route. In addition, numbers are assigned to closed circuits or roads defined within the communication network,
The header of the packet includes an area that indicates the number of the cycle or road used to transfer the baguette, and an area that displays the number of the destination node when the packet is transferred along the cycle or road. , a node maintains a routing table that indicates the correspondence between the number of a cycle or road and the link that sends the packet, and for packets arriving from a link, an area that indicates the number of the destination node. Decrease the value by 1, and if the value is O, it is determined that the packet is addressed to the own node. If the value is 1 or more, the packet is sent by referring to the route or road number included in the header in the routing table. The second feature is to select links.

The conventional technology is that multiple originating and receiving node pairs use a common closed path or part of a road as a route, so that the routes between these node pairs can share a field in a routing table. In order to achieve this efficiently, the number of the cycle or road is displayed in the header of the packet, and each node is equipped with a routing table that shows the relationship between this number and the output link. The difference is that in order to make the determination easier, the number of the destination node is displayed in the header, and each time it passes through a node, this number is decremented by 1, and the packet continues to be forwarded until it reaches 0. .

(Example) FIG. 1 is a diagram for explaining the present invention in detail.
2. −． 7 are nodes a, b, c.

. . , j is a link, L, , L, , L2 is a closed path defined within the communication network, and the arrow indicates the direction of packet transfer.

FIGS. 2(a), (b), and (c) are diagrams illustrating the header structure of a packet in this embodiment,
is an area indicating the cycle number (hereinafter referred to as area A), B is an area indicating the number of the destination node (hereinafter referred to as area B), and CI is a call identifier. FIG. 3 is a block diagram of the node for explaining the operation of the node in this embodiment,
FIG. 4 is a routing table in this embodiment.

In this embodiment, the procedure for transferring a packet from node 0 to node 6 will be described below. Transfer from node 0 to node 6 is possible by using a closed circuit and setting the third node from node 0 as the destination node (FIG. 1). Therefore, node 0 gives the value "01" indicating that the structure of the header of the packet to be transferred to node 6 is to use a closed circuit in area A, as shown in FIG. 2(a), and in area B, It gives the value "old 1" indicating that the third node is the destination node, and sends it to the next node, 1, in a closed circuit.

To explain the processing at node l using FIG. 3, link a
A packet arriving from the human-powered link IO corresponding to 10 first decreases the numerical value in area B by 1 by the processing mechanism 11 of the header area B to become "old 011." Next, the packet is sent to the output destination identification unit 12. If area B is 0 (000 in binary notation), the output destination identification unit 12 determines that the packet is addressed to its own node, and if area B is not 0, it sends the value of area A to the routing table 14. Then, the output link corresponding to the number of the closed circuit indicated by the area A is determined.The packet is transferred via the packet switch 13 to the output light identified by the operation of the output destination identification section.

Now, since area B of the packet sent to node 6 via cycle L1 is "old O" as described above, the value of area A is "
01" to the routing table. Searching for the entry "01" in the routing table shows that the output link is b, and the packet is sent to link b by the packet switch. The packet arrives at node 2 through link b. As a result of the processing in node 1, its header becomes as shown in Fig. 2(b). In node 2, as in the case of node 1, area B is decreased by 1 and is set to "0 old".
Then, it searches the routing table and sends it to link f. The header of the packet arriving at node 6 through link f is as shown in FIG. 2(C). node 6
Now, if area B is decreased by 1, it becomes "000", so it can be seen that this is the destination node. Note that the transfer destination terminal uses <cr, which is the same as in the conventional method.

In this way, in this method, the routing table is searched by the field indicating the cycle number in the header, so it is sufficient to have that field as many as the number of cycles passing through the node. For example, in the case of node 1, the situation is as shown in FIG. In this routing table, packets using the same cycle can share the same column even if the originating and terminating nodes are different. Further, determining whether or not the destination node of a packet is the own node requires only comparing a part of the header with 0, and does not require a table.

As a result, in a communication network where the conventional method required 15 columns in the routing table, the present invention has the effect of reducing the number of columns to 3.

(Effects of the Invention) As explained above, the same column of the routing table is shared for routes between multiple pairs of originating and terminating nodes, and the routing table is used to determine whether or not the own node is the destination node of the packet. This has the advantage that the number of columns in the routing table is reduced and the memory cost for storing it is reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a closed circuit defined in a communication network in an embodiment of the present invention, FIG. 2 is a configuration diagram of a packet header part in the embodiment, and FIG. 3 is a diagram of a node configuration in the present invention.
FIG. 4 is an example of a routing table according to the present invention, FIG. 5 is an example of a vP defined between a source node and a destination node in a conventional method, and FIG. 6 is a packet structure of a conventional method with VPI and CI. FIG. 7 shows a conventional node configuration including a routing table representing the correspondence between Vl'I and output links, and FIG. 8 shows an example of a routing table according to the conventional method. 10, 10°, 10″...input link, 11...
Processing section of area B, l 2-- Cutting edge identification section, 13-
... Packet switch, 14-... Routing table, 15, +5°, 15"... Output link, 20, 2
0°, 20”...Input link, 21...Blade tip identification section, 22-...Packet switch, 223-...
Routing table, 24, 24°, 24″...output link.

Claims (1)

[Scope of Claim] In a packet communication method in which a packet is transferred from a source node to a destination node according to information in a header part in a communication network in which a plurality of nodes are connected by links, a plurality of nodes in the communication network The information in the header of the packet includes the path that includes both the originating node and the destination node, and the number of nodes along the path from the source node to the destination node. Characteristic packet communication method.