JP2535874B2 - Routing control method for packet switching network - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a routing control system of a packet switching network, and more particularly to a routing control system suitable for detour control when the queue length of a line is abnormal.

[Conventional technology]

The telegram sent from the terminal is transmitted to the exchange through the subscriber line, assembled into packets there, and then stored in the memory of the exchange. The packet stored in the memory is packet-multiplexed with the packet sent from another terminal and sent to the high-speed transmission line. The packet is transmitted through the packet switching network according to the control information and is delivered to the packet switching device that accommodates the receiving terminal. However, the transmission route is not constant, and different routes can be selected depending on the state of the packet switching network. It is possible. That is, it is possible to check the congestion state in the network at that time and select an empty route. This is called routing control. Therefore, when performing routing control,
Only a specific route will not be overcrowded and will not be congested.

Conventionally, as a standard for performing routing control,
(A) Minimize the delay of packet transmission time, (b) Minimize the packet transmission distance, and so on. In general, each link of the packet switching network is given a weight corresponding to the above standard, and routing control is performed to minimize the weight.

As a routing control method of a packet switching network, for example, there is a method described in "Computer Networks" by Tanenbaum. According to this method, each switch has a queue length state as a route state of its own line. Is monitored, and if it is abnormal, it is rerouted to the queue of another line.

However, in the conventional routing control method, since the stability in routing is not taken into consideration, if the path is simply bypassed, the effect will reach all the destination exchanges, and the inversion of the arrival packet will occur in many destination exchanges, Or, there is a possibility that traffic may concentrate on the detour line.

[Problems to be solved by the invention]

In this way, in the conventional routing control method, when a line is detoured to another line due to an abnormal queue length, etc., if the line is in an abnormal state, it is mechanically detoured to another line with a short or short queue length. Was. That is,
At this time, no consideration is given to performing step-by-step detours for each destination exchange, and since all the destination exchanges that have that line as the transmission direction are targeted for detour, traffic will not flow to the destination line. The possibility of concentration is great. In addition, the stability at the time of changing the routing is poor, and the probability that the arrival order of packets will be reversed is increased in all destination exchanges.

An object of the present invention is to improve these conventional problems, to avoid packet concentration and inversion of packet arrival order in all destination switches, and to perform packet switching with high stability when diverting packets. It is to provide a routing control method for a network.

[Means for solving problems]

In order to achieve the above object, the routing control method of a packet switching network according to the present invention is applicable to the case where a packet is transmitted from one line of two or more lines which respectively transmit a packet passing through a plurality of destination exchanges. When the line queue length exceeds a predetermined value and an abnormality occurs, only the packets of a specific destination exchange among the plurality of destination exchanges are diverted to another line, and when the queue length abnormality continues, another It is characterized in that the destination exchange is selected, the packet of the exchange is also diverted to another line, and when the queue length abnormality is resolved, the diverted packet of the destination exchange is restored.

[Action]

In the present invention, when the queue length is abnormal in the line to be transmitted, that is, when the queue length becomes larger than the specified value, the destination exchanges to be transmitted in the line are used as a unit to detour step by step. This prevents concentration of packets to a specific destination exchange and reversal of the arrival order of packets.

That is, in the routing control method of the present invention, when a line has an abnormal queue length, the same relay hop as the line having the queue length error in the destination exchanges that are sending packets from the routing table is used. A switch having a certain number or a destination switch having another line whose relay hop number is larger by one is selected, and one switch is determined according to an appropriate algorithm. When the destination exchange has the same number of relay hops, it bypasses the traffic of the line causing the queue length abnormality to that exchange, and in the case of the destination exchange having the number of relay hops increased by 1, The routing table is changed so that the traffic of the exchange is divided into two. In addition, when the line whose traffic is detoured by the above control has an abnormal queue length, it is determined on the assumption that such processing is being performed, and the reverse processing is performed to detour. Restore the existing traffic, or perform detour processing.

As described above, according to the control of the present invention, it is possible to perform appropriate detour processing stepwise according to the traffic volume of each line.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a configuration diagram of a packet switching network to which the present invention is applied, and FIG. 3 is a diagram showing a routing table of the packet switching device 1 in FIG.

In the packet switching network of FIG. 2, the packet switches numbered 1 to 9 are lines l ₁ , l ₂ ,.
・ Connected by. Here, the queue length abnormality of the lines l ₁ and l ₂ accommodated in the packet switch 1 will be described.

The packet switch 1 transmits packets addressed to the other packet switches 2 to 9 through the lines l ₁ and l ₂ , but in that case,
It is assumed that the data is transmitted according to the values in the routing table 100 shown in FIG.

The routing table 100 shows the number of relay hops when the line l ₁ is used when transmitting a packet to each destination exchange.
It stores 1 and the number of relay hops 102 when the line l ₂ is used, and each value of the actual transmission route 103. For example, exchange 2
Since the number of relay hops when transmitting via line l ₁ is 1, and the number of relay hops when transmitting via line l ₂ is 3, it is shown that the actual transmission route is l _1. ing.
Similarly, since the number of hops when transmitting to the exchange 3 via the line l ₁ is 2 and the number of hops when transmitting to the switch l ₂ is 4, the actual transmission route is l _{Is 1} . Further, in the case of the destination exchange 5, since the number of relay hops of the lines l ₁ and l ₂ is the same value 2, the actual route is
Both l ₁ and l ₂ are used. This is the same for the destination exchanges 8 and 9, and when transmitted via the lines l ₁ and l ₂ , the exchange 8 has a hop count of 3 and the exchange 9
The number of hops is four, and all have the same value.

FIG. 4 is a diagram showing a general hardware configuration example of the packet switches 1 to 9 in FIG. here,
Although only the packet switch 1 is shown, the other packet switches have substantially the same configuration.

In the exchange 1, a memory 16 for storing a group of commands for exchange processing and necessary data for each subscriber, trunk line, etc.
A processor 17 for executing the above instruction group and line interface adapters 191 to 194 for connecting a subscriber line or a trunk line to the memory 16 and the processor 17 are connected to each other via a bus 18. The packet switch 1 normally accommodates a plurality of subscriber lines and a plurality of relay lines, and packets received from these lines are temporarily stored in the memory 16 via the line interface adapters 191 to 194. After that, the processor 17 selects a transmission line for each packet according to its destination, and transmits it via the corresponding line interface adapters 191 to 194. A routing table 100 shown in FIG. 3 is stored on the memory 16, and the processor 17 refers to the routing table 100 to select a transmission line. The line interface adapters 191 to 194 are provided with transmission waiting queues Qf, Qg, and Qh generated in the respective line adapters, and the processor 17 refers to these queues Q to execute the bypass processing.

FIG. 1 is a processing flowchart of routing control showing an embodiment of the present invention. Here, an instruction step sequence executed by the processor 17 in the packet switch 1 shown in FIG. 4 is shown.

First, the queue lengths of lines l ₁ and l ₂ are counted (step
201), if there is a difference in their queue lengths (now,
Queue length of the line l ₁ is assumed to be larger than the queue length of the line l ₂₎ (step 202), the queue length greater access and examine whether already been bypassed (step 204 ). Routing table 1 shown in Figure 3 before and after
00 is a case where the detour processing has not been performed yet. Less than,
The case where the detour processing is not performed (that is, step 205 and subsequent steps) will be described.

In this case, first, a destination packet switch that divides traffic into two or more routes to the same destination (hereinafter referred to as load distribution) is obtained from the routing table 100 shown in FIG. 3 (step 205). . As is clear from FIG. 2 and FIG. 3, the destination exchanges whose loads are distributed are the exchanges 5, 8 and 9. One of these is selected according to an appropriate algorithm (step 206). Now, it is assumed that the selected exchange is 9.
The load distribution is stopped and only the line with a short queue length is used as the transmission route (step 207).

5 (a) and 5 (b) are diagrams showing packet paths to the exchange 9. As shown in FIG. Packet switch 1 to lines l ₁ and l ₂
A packet transmitted to the destination exchange 9 via the
As shown in FIG. 5 (a), the route F ₁ or the line l ₁ reaches the exchange 9 via the exchanges 2, 3 and 4, and the route F ₂ or the line l ₂ passes the exchanges 6, 7, and 8. It reaches the exchange 9 via. Since both routes F ₁ and F ₂ have the same number of relay hops, it is normal to distribute the load by transmitting packets in half. However, in the routing control according to the present embodiment, the processing for distributing the load to the line l ₁ and the line l ₂ for the destination exchange 9 is stopped. That is, the line l _{1 is used} as the transmission route to the destination exchange 9.
Will be removed from the registration 103 of the transmission route in the routing table 100. As a result, as shown by the solid line in FIG. 5 (b), only the route F ₂ is provided. That is, in FIG. 5 (a), the packet was transmitted to the destination exchange 9 via the two routes F ₁ and F ₂ , but only one route F ₂ was used.
As a result, the load on the line l ₁ of the packet switch 1 is reduced.

Next, as a result of performing the above routing control, if the queue length of the line l ₁ is still larger than the queue length of the line l ₂ ,
It is necessary to sequentially perform the same control on the destination exchanges 8 and 5. If the destination exchanges 8 and 5 are also subjected to the above-mentioned processing, and as a result, there is no exchange distributing traffic, the number of relay hops of the line l ₂ is ₁ than that of the line l 1. The traffic is distributed to a destination exchange that is as large as possible (steps 208, 20).
9).

When allocating traffic to a destination exchange whose relay hop count is one greater than line l ₁ , specifically, one l greater than line l ₁ is included in routing table 100.
_Since there are only four exchanges with ₂ , the line l ₂ is registered as the transmission route of the destination exchange 4.

On the other hand, when there is a difference in the queue lengths of the lines l ₁ and l ₂ , when detouring to the line l ₁ having a large queue length, if detouring to one exchange, then detouring to that switch, and two If there is a detour to the above exchange, one of them is selected and the detour of the exchange is immediately stopped (step 210). This process is repeated to restore the detoured packet of the destination exchange.

FIG. 6 is a diagram showing the contents of a routing table showing another embodiment of the present invention.

In the above embodiment, the number of relay hops to the destination exchange is 10
For 1 and 102, the value was not changed, but in the present embodiment, when a queue length error occurs,
It is possible to increase the number of relay hops to all the destination exchanges of the corresponding route by 1, and change the transmission route from the number of relay hops at that time. For example, in the exchange 1 that originally had the routing table 100 shown in FIG.
_{When a} queue length abnormality occurs in the transmission queue of ₁ , the relay hop count of the line l _{1 in} the table of FIG. 3 is incremented by 1 for all destination exchanges. FIG. 6 shows the result. The destination exchanges whose transmission routes are changed in the table 100 according to the addition result are the packet exchanges of 4, 5, 8 and 9. In other words, since the number of relay hops on both lines is the same in the exchange 4, it is necessary to distribute the load to the actual transmission route, and in the exchanges 5, 8 and 9, there is a difference in the number of relay hops on both lines, so the hop It is necessary to use the line l ₂ with a small number as the transmission route.

In the present embodiment, these transmission routes are not changed at once, and the destination exchange 4, by an appropriate algorithm,
First, select one from 5, 8 and 9 and change the transmission route. As a result, if the queue length abnormality is not resolved, one is selected from the remaining applicable destination exchanges. This process is repeated unless the abnormal queue length is resolved. If the queue length error is not resolved even after changing the transmission route for all the applicable destination exchanges, add 1 to the number of relay hops and perform the same process as above from the result, and perform the transmission route. To change.

As described above, in the routing control of the packet switching network of the present invention, when each exchange determines the transmission route by referring to the queue status of the line of its own station, it is distributed over a plurality of routes, or Only in the destination exchange having a route whose number of relay hops differs by 1, only the transmission route of one destination exchange is changed in one process. Therefore, the probability of fluctuation of the traffic bias due to the change of the routing route is calculated. It can be reduced and the routing control can be implemented in detail.

〔The invention's effect〕

As described above, according to the present invention, the destination exchanges are used as a unit, and detours are performed stepwise for each destination exchange according to the state of the queue length abnormality of the line. Therefore, traffic is concentrated at the detour destination, or It is possible to improve the stability at the time of changing the routing without reversing the arrival order of the packets in the destination exchange.

[Brief description of drawings]

FIG. 1 is a flow chart of a routing control process of a packet switch according to an embodiment of the present invention, FIG. 2 is a diagram showing a configuration example of a packet switch network to which the present invention is applied, and FIG. 3 is each of FIG. FIG. 4 is a diagram showing an example of a routing table provided in the exchange, FIG. 4 is a diagram showing an example of the hardware configuration of the packet switch in FIG. 2, FIG. 5 is a diagram showing an example of changing the communication route in the present invention, and FIG. It is a figure of the routing table which is another Example of this invention. 1: Packet switch, 16: Memory, 17: Processor, 18: Bus, 191-194: Line interface adapter, 100: Routing table, 101, 102: Number of relay hops for each line, 103: Actual transmission route, Qf, Qg, Qh: Line queue, F ₁ , F
₂ : Communication path.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Kano, Takashi Kano 4-6 Kitahama, Higashi-ku, Osaka, Osaka, Hitachi West Software Co., Ltd. (56) Reference JP 61-189747 (JP, A) JP 60-177761 (JP, A) JP 57-11559 (JP, A) JP 63-110843 (JP, A)

Claims (2)

(57) [Claims] 1. A routing of a packet switching network comprising a routing table storing the number of transit exchanges to each destination exchange, and determining a packet transmission route by referring to the contents of the routing table and the queue length state of each line. In the control method, when a packet is transmitted from one line of two or more lines that respectively transmit a packet passing through a plurality of destination exchanges, the queue length of the line exceeds a predetermined value and an abnormality occurs , Divert only packets of a specific destination exchange among the plurality of destination exchanges to another line,
If the queue length error continues, select another destination switch and divert the packet of the switch to another line. When the queue length error is resolved, restore the packet of the bypassed destination switch. A routing control method for packet-switched networks. 2. When selecting the specific destination exchange, when no queue length abnormality occurs, a packet is sent to a line having the smallest number of relay exchanges up to the destination exchange, and when the queue length abnormality occurs, the queue The number of transit exchanges to each destination exchange of the line in which the long abnormality has occurred is increased by one, and the destination exchange to be detoured is selected based on the resulting numerical value. A routing control method for packet-switched networks.