JPH0831880B2 - Packet switching method - Google Patents

Description

The present invention relates to a switching system, and more specifically to a packet switching system.

(Prior Art) A packet switching system uses an asynchronous self-routing multi-stage switch having a buffer function as a unit switch. When exchanging a packet having a routing tag indicating a destination in the header portion with this switch, the first half of the multistage switch operates as a load distribution network, and the second half of the multistage switch operates as a routing network. Since packets arrive irregularly at the packet switching system, it is necessary to suppress the occurrence of internal congestion within the switching system. As a method of suppressing internal congestion, it is considered that a buffer function is added to a unit switch and a load distribution network is provided in the first half of the multi-stage switch to make the load as uniform as possible in the network. As a load distribution method in this load distribution network, a method of randomly distributing a load to links and a method of sending a packet to a relatively vacant link depending on the congestion of buffers in each unit switch are considered.

When a series of information packets are input from the input port of the asynchronous self-routing multi-stage switch to the load distribution type distribution network, the distribution unit switch of the distribution network randomly outputs these packets to the output terminal. The load distribution network distributes the load as evenly as possible. A series of packets input from the load balancing network to the routing network are transmitted via another link in the routing network with a target output port as a destination. In the case of a high-speed packet in which the interval of transmission of packets is not sufficiently large compared to the information transfer capacity of each link, the packet transmitted by the busy link may be overtaken by the packet input later. For this reason, a series of packets whose order is reversed is switched at the output port so that the order of the packets is the one input to the multistage switch.

(Problems to be Solved by the Invention) As described above, in the load balancing method according to the related art, when the interval between packets generated in one communication approaches a predetermined limit within the information transfer capability of each link, In some cases, a packet input to the asynchronous self-routing multistage switch is overtaken by a packet input later. Therefore, in order to correctly convey a series of information,
It is necessary to rearrange the packets arriving at the output port in the order in which they are input to this switch, and this rearrangement is very large.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks of the prior art and to provide a packet switching system that realizes an asynchronous self-routing multi-stage switch that does not overtake packets in a series of packets.

(Means for Solving Problems) In order to solve the above-mentioned problems, the present invention provides a plurality of 2N (N
Is a natural number), in a packet switching system having an asynchronous self-routing multi-stage switch that exchanges packets arriving at input ports and sends out from the plurality of output ports, the self-routing multi-stage switch is connected to an input port,
A load distribution network that identifies whether the packet is a high-speed packet or a low-speed packet based on the routing information included in the packet prior to the communication information of the packet, and that distributes the load of the input packet according to the identification. A routing network that is connected to a distributed network and that routes a packet input to an output port according to the routing information of the packet, and a series of packets in one communication designated as a high-speed packet by the routing information is input. When input to the load balancing network from the port,
A series of packets are transmitted through the same route in the load balancing network and are routed to the output port in the routing network, so that the series of packets reach the output port in the order in which they are input to the load balancing network.

(Operation) According to the present invention, when a series of packets whose routing information is high-speed packets is input to the load distribution network, the load distribution network determines that the input packet is a high-speed packet based on the routing information of these packets. Identify things. Then, the routing information of these packets is transmitted through the same route in the load balancing network. A series of packets is
After being transmitted through the same route in the load distribution network, the routing network routes the packet to the output port according to the routing information, so that a series of packets reach the output port in the order of input to the load distribution network.

(Embodiment) Next, an embodiment of the packet switching system according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, there is shown a configuration example of an asynchronous self-routing multi-stage switch applied to an embodiment of a packet switching system according to the present invention. The self-routing multi-stage switch has input ports 100-107 and output ports 110-117.
And the load distribution network 10 having two stages of distribution unit switches 120 and the routing network 20 having three stages of routing unit switches 130 are connected by links 308 to 315. . Load balancing network 10 is an input port
It is a network that distributes input packets from 100 to 107 as evenly as possible. The routing network 20 is a banyan network that routes to a predetermined output port according to destination information 182 of a packet described later. The asynchronous self-routing multi-stage switch applied to the present invention is basically larger in scale than that shown in FIG.

The input ports 100 to 107 are connected to the input terminals of the four dispersion unit switches 120 in the preceding stage every two input ports. The distribution unit switch 120 has two input terminals and two output terminals, and selects an output terminal according to a routing tag having a buffering function, a packet type bit 180 described later, and a load distribution network transmission information 181. It has an output selection switch function. The output terminals of the dispersion unit switches 120 in the front stage are connected to the four output ports in the rear stage via the links 300 to 307.
It is connected to each input terminal of one dispersion unit switch 120.

The output terminals of the downstream unit switches 120 are connected to the respective input terminals of the four routing unit switches 130 of the first stage of the routing network 20 via links 308 to 315. Routing unit switch 130
Has a buffering function and an output selection switch function for selecting an output terminal aiming at a destination output port, and has two input terminals and two output terminals. The output terminals of the first-stage routing unit switch 130 are respectively linked by a link 316.
~ 323 through 4 second routing unit switches 1
Connected to each of the 30 input terminals. Also, the output terminals of the second-stage routing unit switch 130 are
It is connected to the respective input terminals of the four unit routing switches 130 of the third stage via links 324 to 331. Third
The output terminals of the stage unit switch 130 are output ports 110 to 117.
Respectively connected to.

FIG. 2 shows an example of the frame structure of a packet used in this embodiment. The type bit (S) 180 at the head of the packet is a type bit indicating whether the packet is a high speed packet or a low speed packet. A high-speed packet is a packet in one communication in which the interval of generated packets is not sufficiently larger than the information transfer capacity of each link of the switch, and a low-speed packet is the interval of generated packets in the information transfer capacity of each link. A packet in one communication that is sufficiently large in comparison is shown.

The transfer information (LD) 181 is load distribution network transfer information indicating a route for transferring the load distribution network 10 when the type bit 180 indicates a high speed packet. That is, the high-speed packet is controlled by the distribution unit switch 120 according to the transmission information 181 so as to proceed through the load distribution network 10 by a fixed route. Also,
A packet whose type bit 180 indicates a low-speed packet is not fixed in the transmission route in the load distribution network 10 and is transmitted by the distribution unit switch 120 by selecting an empty link for each packet.

Destination information (DA) 182 is destination information including information indicating a target output port, and the packet is routed in the routine network 20 by this information 182. Communication information (I) 183
Is information data to be sent to the device indicated by the destination information 182. When the information data is long, this information data is divided into a plurality of packets. A packet obtained by dividing one piece of information data into a plurality of packets in this way is called a series of packets.

A series of packets from input port 100 (A0) 500 / (A1)
An operation of inputting 501. (A2) 502 and packets (B0) 600. (B1) 601 and outputting a series of these packets to the output port 110 will be described. Packets 500, 501 and 502 are
Each is a packet designated as a high-speed packet by the type bit 180. Ie these packets 500-502
Is a packet in one communication in which the generated packet interval is not sufficiently large as compared with the information transfer capability of each link. Further, the packets 600 and 601 are packets in one communication in which the type bit 180 indicates a low-speed packet and the interval between the generated packets is sufficiently larger than the information transfer capability of each link.

When the high-speed packet 500 is input to the distribution unit switch 120 in the preceding stage of the load distribution network 10, the type bit 180 of this packet 500 controls the route in the load distribution network 10 to be fixed. Then, the transmission information 181 of this packet 500
Thus, the transmission route of the load distribution network 10 is fixed.

For example, the transmission information 181 of the packet 500 is the load distribution network 10
In the case of the information transmitted through the link 300 and the link 308 of the link 300, the packet 500 input to the distribution unit switch 120 at the preceding stage is the link 300-the distribution unit switch 120 at the subsequent stage.
It is sent to the routing unit switch 130 of the first stage of the routing network 20 by the route of the link 308. In the routing network 20, the packet 500 is transmitted to the target output port 110 by the destination information 182. That is, the route reaches the output port by the route of the first stage routing switch 130-link 316-the second stage routing unit switch 130-link 324-the third stage routing unit switch 130-output 350. The packet 500 is switched through the load distribution network 10 and the routing network 20 by the route R1.

Packets 501 and 502 have type bits 180 and
Since the routing tags of the transmission information 181 and the destination information 182 are the same as those of the packet 500, they are sent to the output port 110 by the route R1 similar to that of the packet 500. As described above, since the high speed packets 500, 501 and 502 are transmitted by the same route, that is, the route R1, packet overtaking occurs in the load distribution network 10 or the routing network 20 and the output port 110
The order of the packets does not change when arriving at.

The low-speed packets 600 and 601 are not fixed in the transmission route of the load distribution network 10 by the type bit 180, and are transmitted by selecting a vacant link for each packet. Packet 600
Is sent to the routing unit switch 130 of the first stage of the routing network 10 by the route of link 301-distribution unit switch 120-link 312, for example. And this packet 6
00 indicates the destination unit information 182 of the first-stage routing unit switch 130-link 320-the second-stage routing unit switch 130-link 328-the third-stage routing unit switch 130-output 350-output port 110. Output port 1 at root
To reach 10. The packet 600 is switched through the load distribution network 10 and the routing network 20 by the route R2.

In addition, packet 601 is link 301-distribution unit switch
The route 120-link 313 is sent to the unit switch 130 for routing in the first stage. Packet 601 is the destination information
182 includes a first-stage routing unit switch 130-link 322-a second-stage routing unit switch 130-link
328-Unit switch for third stage routing 130-Output 350
-Sent to the output port 110 by the route of the output port 110.
The packet 601 is switched through the load distribution network 10 and the routing network 20 by the route R3.

The low-speed packets 600 and 601 have sufficiently large packet generation intervals as compared with the information transfer capability of each link of the self-routing multistage switch according to the present embodiment. Therefore, even if each link is congested and the linking is performed by the distribution unit switch 120 and the routing unit switch 130 until the link becomes free, the packet 601 does not overtake the packet 600.

FIG. 3 shows a conventional asynchronous self-routing multistage switch. The distribution unit switch 700 that constitutes the load distribution network 50 is the distribution unit switch 120 according to the present embodiment.
Unlike routing tag type bit 180 and transmission information 1
There is no output selection function to select the output terminal according to 81. Therefore, the distribution unit switch 700 of the load distribution network 50 randomly outputs the input packets regardless of whether they are high-speed packets or low-speed packets to the links in order to distribute them as evenly as possible within the load distribution network 50.

For example, as shown in the figure, a series of high-speed packets (C0) 800, (C1) 801, (C2) 802 are output from the input port 100 in order by routes R10, R11 and R12, respectively.
When sent to 110, the order of the packets may be mixed up. This is because the distribution unit switch 700 or the routing unit switch 130 buffers packets until the link becomes free depending on the congestion state of each route through which the packet is transmitted. When, for example, the packets 800, 802, and 801 arrive at the output port 110 in this order, the output port 110 swaps the packets 802 and 801 to arrange the order. The exchange of packets performed at the output port 110 becomes very large.

On the other hand, in this embodiment, the type bit 18
A routing tag of 0 and transmission information 181 is added, and the routing tag determines the output of the distribution unit switch 120. That is, when the type bit 180 is a high-speed packet in which the order of a series of packets may be changed, the transmission information 181 causes the series of high-speed packets to reach the output port by the same route. Therefore, the order of packets does not change regardless of the congestion state of the link. Therefore, there is no need to change the order of packets at the output port. Further, according to this embodiment, since each link can be used efficiently, the throughput is improved.

In this embodiment, the self-routing switch applied to the present invention is the 8 × 8 switch, but the self-routing switch is not limited to this. That is, the self-routing switch is a 2N × 2N switch having 2N input ports and 2N output ports, respectively, and the load distribution network is from the first stage to the Kth stage in the first half and the (K + 1) th stage in the second half.
The ( ^MK ) stages (2 ^MK = 2N) from the stage to the Mth stage are also advantageously applied to the asynchronous self-routing multistage switch of the routing network.

According to the present invention, the routing information of a packet includes a type bit indicating the type of a high-speed packet or a low-speed packet and a transmission information bit indicating a route for transmitting a load distribution network in the case of a high-speed packet. It is used in combination with the method of selecting the same link for a series of packets during one communication in the load balancing network according to the information and the method of selecting a relatively free link for each packet. For this reason,
At the same time as there is no load imbalance, a series of packets input from the input port in one communication reaches the output port in the input order. Therefore, it is not necessary to change the order of packets at the output port,
Also, the link can be used efficiently, and the effect of improving the throughput can be expected.

[Brief description of drawings]

FIG. 1 is a switch configuration diagram showing an embodiment of an asynchronous self-routing multi-stage switch applied to a packet switching system according to the present invention, and FIG. 2 is a frame of a packet used in the asynchronous self-routing multi-stage switch of FIG. FIG. 3 is a frame configuration diagram showing the configuration, and FIG. 3 is a switch configuration diagram showing an asynchronous self-routing switch according to the prior art. Explanation of symbols for main parts 10 …… Load distribution network 20 …… Routing network 100 to 107 …… Output ports 110 to 117 …… Input port 120 …… Distribution unit switch 130 …… Routing unit switch 180 …… Type bits 181 …… Transmission information 182 …… Destination information

Claims (2)

[Claims] 1. A packet switching system having an asynchronous self-routing multistage switch for exchanging packets arriving at a plurality of 2N (N is a natural number) input ports and transmitting the packets from the plurality of output ports, wherein the self-routing multistage switch comprises: , Connected to the input port, the routing information included in the packet prior to the communication information of the packet,
A load distribution network that identifies whether the packet is a high-speed packet or a low-speed packet, and that distributes the load of the input packet according to the identification, is connected to the load distribution network, and uses routing information of the packet. A routing network for routing packets input to the output port, wherein a series of packets in one communication designated by the routing information as a high-speed packet is transferred from the input port to the load balancing network. When input, the series of packets are transmitted through the load distribution network through the same route, and are routed to the output port in the routing network, so that the series of packets are transmitted to the load distribution network. A packet switching system characterized in that the packets arrive at the output port in the order of input. 2. The packet switching system according to claim 1, wherein the routing information of the packet is a type bit indicating whether the packet is a high speed packet or a low speed packet, and the type bit is a high speed packet. The packet switching system is configured by a transmission information bit into which information of the transmission route of the load balancing network is inserted when the above is indicated, and a destination information bit including information indicating the output port.