JPH0614644B2 - Packet switching trunk line selection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Use of the Invention] The present invention relates to a transmission line from among a plurality of relay lines set up with another station when transmitting a packet to another station in a packet switching network. The present invention relates to a packet-switching relay line selection method suitable for selecting lines so that each line is used evenly.

BACKGROUND OF THE INVENTION Generally, in a packet switching network, a plurality of relay lines are set up between switching stations in order to ensure throughput and maintain reliability. When transmitting a packet to another station, the switching center first determines the relay route based on the destination information in the packet header, and then determines the line number (outgoing line) of the transmission line in the relay route. Number).

When deciding the transmission line, it is necessary to consider that multiple lines should be used as evenly as possible in order to reduce the packet delay time in the network.

Conventionally, when a packet is transmitted to a relay line in a packet transmission station or a packet relay station, a method is used in which the outgoing line is randomized according to the line number (incoming line number) at which the packet entered the switching center. That is,
When selecting an intra-route line after determining the route, the exchange determines the line to be transmitted using the incoming line.

FIG. 1 is a block diagram of a switching network for explaining the trunk line selection logic according to the above method.

In FIG. 1, P is a packet switch, and R1, R
2, R3 and R4 are relay route numbers viewed from the exchange P. In addition, each of the routes R1, R2, R3, and R4 has 2 to 3
Book lines (L _ij , i = 1 to 4, j = 1 to 3) are set.

FIG. 2 shows the structure of the route / line selection table in the switching network of FIG. 1, where T0 is the one for obtaining the relay route number to which the packet is to be sent from the destination a in the packet header. A route selection table, T4 is an example of a line selection table for obtaining the outgoing line number of a line to be transmitted from the lines directed to the route R4. H
LN 'is a remainder obtained by dividing the line number HLN of the incoming line by the number of lines of the outgoing line.

Next, a conventional route / line selection processing method will be described with reference to FIG.

First, when a packet is received from the line, the number HLN of the line (incoming line) from which the packet is transmitted is set in the header of the packet (301, 302). Next, the destination station number a is extracted from the packet, and the route selection table T0 shown in FIG. 2 is indexed by the destination station number a to obtain the route number (303, 304). Once the route number is obtained, it is recognized that the packet should be sent on the route indicated by that number. Furthermore, in order to determine the transmission line from the plurality of lines set in that route, the line selection table for that route is accessed,
The outgoing line number (L _ij ) is obtained by indexing with HLN '(3
05). The packet is transmitted to the line indicated by L _ij (306).

Specifically, a packet arriving from the line L11 and transferred to the route 4 will be described as follows.

When the exchange P receives a packet from the line L11, the destination number a is extracted from the header of the packet, and the route selection table T0 is indexed by this number. When the value T4 is obtained from FIG. 2, it is recognized that this packet is a packet to be sent to the route number R4. Next, the line selection table T4 is accessed and indexed by the remainder (HLN ') obtained by dividing the incoming line number HLN by the number of outgoing lines set in the outgoing route (R4). If this remainder is 1, the transmission line L42 is obtained as shown in FIG.

As described above, in the conventional method, the traffic is randomized on a line-by-line basis for incoming lines, and packets with the same incoming line number and outgoing route are all sent to the same relay line. It will be.

Therefore, the conventional method has the following problems.

(1) If the number of incoming lines and the number of outgoing lines are different, such as when the number of incoming lines is 3 and the number of outgoing lines is 2, the load on the outgoing lines will be unbalanced.

(2) When an incoming line contains a line whose line speed is higher than that of another incoming line, a large load is applied to a specific outgoing line.

Specifically, looking at the packets transferred from the routes R1 to R4 in FIG.
42 is selected, L41 from L12, L13 from L12
From the above, L42 will be selected. That is, the line L42 is loaded with twice as much load as the line L41.

If L11 is several times faster than the other incoming lines, L42 will be loaded several times as much as L41.

[Object of the Invention]

An object of the present invention is to solve the above-mentioned problems of the prior art, even if the number of incoming lines and outgoing lines is different or the incoming line speeds are non-uniform, packet traffic (load) It is to provide a packet-switching trunk line selection method capable of selecting trunk lines so as to evenly distribute packets.

[Outline of Invention]

In order to achieve the above object, the packet relay line selection method of the present invention is a source switching center of a packet switching network, wherein the source switching center, when originating each call, the destination station number of the call and the number of each call. (Hereinafter referred to as CIDX) is added, and the destination station number and the CIDX are set in the headers of all packets of the subsequent call, and the CIDX is calculated from the number M of trunk lines of the originating switching center or the relay switching center. A large value N is sequentially given by the originating exchange in the order of occurrence of calls by the modulo N, and the originating exchange or the relay exchange has first means for associating the destination station number with the route number, and It is provided for each route number and corresponds to the modulo N number below the number of trunk lines, and corresponds to the above-mentioned trunk line number modulo the number of trunk lines M for the number of modulo N beyond the number of trunk lines. Equipped with a conversion table , And has a second means for designating a relay line when the CIDX is given, and when transmitting the packet to the relay line, the originating switching center or the relay switching center selects the first station from the destination station number in the header. It is characterized in that the route number is determined by the means and the relay line number is determined by using the CIDX by the second means corresponding to the route number.

Example of Invention

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram of a switching network for explaining a trunk line selection logic according to an embodiment of the present invention.

P is a packet switch, and R1, R2, R3, and R4 are relay route numbers viewed from the switch P. In addition, each route R
1 to R2, R3, and R4 have two or three trunk lines L
_ij (i = 1 to 4, j = 1 to 3) are set.

It should be noted that CIDX is a number assigned to each call by the originating exchange when the call is originated modulo N (modulo 8 in this embodiment), and is set in the headers of all packets of the subsequent call.

Here, modulo is an arithmetic operation method in which the remainder when the first operation number is divided by the second operation number is the result. Generally, when adding and subtracting with modulo N, the values are 0, 1,
2, ..., N−1, the value of modulo 8 is 0,
There will be eight of 1, 2, 3, 4, 5, 6, 7.

FIG. 5 shows the structure of the route / line selection table in the exchange P of FIG.

T0 is a route selection table for obtaining the relay route number to which the packet is to be transmitted from the destination a in the packet header, and T4 is the outgoing line number of the line to be transmitted from the lines to route R4. 2 is an example of a line selection table for determining The contents of the line selection table T4, which are alternately repeated with L41, L42, L41, ..., are the values of CIDX, that is, the values of modulo 8, 0, 1,
It corresponds to 3, ...

With the above configuration, the exchange P operates as shown in the flowchart of FIG.

First, when a packet is received from the line, the number CIDX assigned by modulo N at the time of setting a logical link (call) is set in the header of the packet (601, 60).
2). Next, the destination station number a is extracted from the packet,
The route selection table T shown in FIG. 5 according to the destination station number a
Index 0 to get the route number (603, 604). Further, the line selection table corresponding to this route number is accessed and indexed by CIDX to obtain the outgoing line number L _ij (60
5). The packet is transmitted to the line indicated by L _ij (606).

Next, the above operation will be described with a specific example.

Upon receiving the packet from the line L11, the exchange P uses the destination station number a of this packet to select the route selection table T0.
To identify the sending route number (R4 in this case),
The line selection table T4 of the transmission route R4 is obtained. Then, the line selection table T4 is set to CIDX (3 in this example).
And the line number L42 for transmitting the packet is obtained.

That is, if the originating exchange assigns the numbers 0 to 7 modulo 8 to the calls originated by the exchange in turn, the line selection table T4 allows each line to be used in turn for each call, so that the lines are evenly used. There is a load, and the line number of the incoming line does not participate in the selection of the outgoing line. This is illustrated in the next example.

C out of the packets from the lines L11, L12, L13
Lines having IDX of 0, 2, 4, 6 are transmitted from the line L41, and lines having CIDX of 1, 3, 5, 7 are line L42.
Sent from. For example, the packet from the line L11 may be transmitted from the line L41 or the line L42 depending on the value of the CIDX.

In this way, the correspondence between the incoming line and the outgoing line is not fixed, and each incoming line and outgoing line are fluidized by the numbers sequentially attached to the calls made by the originating exchange. Is associated with. Therefore, it is possible to make the number of selections of each outgoing line even for numbers having different numbers of incoming lines and outgoing lines.

In the conventional method, as shown in FIG. 1, the packet from the line L11 is always transmitted from the line L42, but in the present embodiment, the packet from the line L11 is CI.
When DX is an odd number, it is sent out from the line L42, and CIDX
Is an even number, it is transmitted from the line L41.
Even if is faster than other incoming lines, the load on L41 and the load on L42 can be equalized compared to the conventional example.

If there is a line speed difference between the outgoing lines, the frequency of the line numbers selected in the line selection table T4 may be proportional to the outgoing line speed, for example, so that the outgoing line speed is taken into consideration. Traffic can be applied to each line as evenly as possible.

The route selection table T0 shown in FIG. 5 may be provided for each packet switch in the packet switching network.
The line selection table must be provided for each route.

〔The invention's effect〕

As described above, according to the present invention, even when the number of incoming lines and outgoing lines is different or the incoming line speeds are uneven, the packet traffic is evenly distributed to each relay line. Therefore, the delay time in the network can be shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of accommodating a trunk line for explaining a conventional route / line selection, FIG. 2 is a conventional route / line selection table, and FIG. 3 is an exchange according to an embodiment of the present invention. FIG. 4 is a flowchart showing an example of accommodating a trunk line for explaining route / line selection according to an embodiment of the present invention, and FIG. 5 is a diagram showing an embodiment of the present invention. A route / line selection table, FIG. 6 is a flow chart showing a line selection operation of an exchange according to an embodiment of the present invention. P: packet switch, R1, R2, R3, R4: route number, T0: route selection table, T4: line selection table, L11 to L43: relay line number, a: destination station number of packet, HLN: incoming line Number, CIDX: A number given to each call by the originating exchange in modulo N at the time of calling.

Claims (1)

[Claims] 1. An originating switching center of a packet switching network, wherein the originating switching center assigns a destination station number of the call and a number for each call (hereinafter referred to as CIDX) when the call is originated. The destination station number and the CIDX are set in the headers of all packets of the subsequent call, and the CIDX is modulo N for a value N larger than the trunk line M of the originating exchange or the transit exchange. The stations are sequentially assigned in the order of call generation. The originating exchange station or the relay exchange station is provided with first means for associating the destination station number with the route number, and is provided for each route number. N
The number of the modulo N, which is equal to the number of the trunk lines and which exceeds the number of the trunk lines, is provided with a conversion table in which the trunk line number modulo the number of the trunk lines M is associated, and when the CIDX is given, the trunk line The sending switching center or the relay switching center, when transmitting the packet to a relay line, assigns the route number from the destination station number in the header by the first means. A packet-switching trunk line selection method, wherein the trunk line number is determined and the trunk line number is determined using the CIDX by the second means corresponding to the route number.