JPH02109445A - Packet identification method - Google Patents

Abstract

PURPOSE:To identify a circulated packet and duplicated packet and to abort them by using address information capable of processing at a repeater and a frame check sequence so as to identify the packet. CONSTITUTION:Repeaters 22-25 store address information of a received packet and a vale of FCS(frame check sequence) for a prescribed time. Every time a packet reaches, the address information and the FCS of the packet are compared with the address information and the FCS stored so far and when they are coincident, the packet is aborted. When dissident, the packet is relayed and the address information and the FCS of the packet are stored. On the other hand, packet communication terminal equipments 15-17 store the sender address information and the FCS as to the packet addressed to itself and compare them with the address information and the FCS of the arrived packet. When they are coincident, the packet is aborted and when dissident, the value is stored.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a method for connecting a plurality of packet-switched communication networks (e.g., local area networks, LANs) to relay devices (e.g., MA
In a communication network interconnected by a packet communication terminal (C bridge), when a packet sent from a source packet communication terminal reaches the destination packet communication terminal via multiple routes, the destination packet communication terminal or intermediate relay device The present invention relates to a packet identification method for identifying this duplicate packet and discarding the packet as being unnecessary because it is duplicated.

[Conventional technology]

Traditional local area networks use address information to identify packets. However, in a communication network where local area networks are connected using relay devices (MAC bridges), this identification method makes it difficult to determine whether the packets are different from each other to the same destination.
The relay device (MAC bridge) cannot identify whether the packet is a circular packet due to a communication route loop that has occurred in the communication network or a duplicate packet that has passed through multiple routes. Furthermore, a situation occurs in which the same packet arriving via multiple routes cannot be identified at the destination packet communication terminal. Therefore, the following method was used to avoid the above situation.

In a communication network consisting of multiple packet-switched communication networks (local area networks) interconnected by relay devices (MAC bridges), the communication path between any two packet communication terminals is determined to be only one, and within the communication network. In order to prevent packets from circulating, the relay devices communicated with each other and the communication network was reconfigured into a logical tree structure. By reconfiguring the communication network into a tree shape in this way, packets are prevented from arriving via multiple routes, and loops are prevented from being formed within the communication network.

The conventional technology will be explained below using the drawings.

FIG. 2 is a block diagram showing a packet-switched communication network connection method based on the prior art. A method for preventing circulation of packets in a communication network and a method for preventing duplicate packets will be explained with reference to the same figure. 1, 2.3 indicate packet communication terminals, 4,
5.6 and 7 represent packet-switched communication networks; 8, 9.
10 and 11 indicate relay devices. 13 indicates the state of the link connecting the packet-switched communication networks 4 and 5;
Reference numeral 14 indicates a link state in which the connection between the packet switching communication networks 6 and 7 is logically disconnected.

A logically disconnected state means that the physical connection line is not disconnected, but packets from the packet-switched communication network 6 are not relayed to the packet-switched communication network 7, and conversely, packets from 7 to 6 are not relayed to the packet-switched communication network 7. This means that the data is not relayed and is discarded by the relay device 11.

At the initial stage of network formation of the communication packet switching type communication network described above, the link state 14 is in a connected state like 13. Each relay device in the communication network sets its own identifier in a special packet (hereinafter referred to as a hello packet) that can only be interpreted by the relay device and sends it out.

When each relay device receives the hello packet, it compares the identifier set there with its own identifier or the maximum value of the relay device's identifier set in the previously received hello packet, and selects the larger identifier. If a hello packet with a small identifier is received, it is relayed, and hello packets with small identifiers are discarded.

By performing this type of auction, the hello packet with the largest identifier will be propagated within the communication network.At this time, if a loop exists within the communication network, the hello packet with the largest identifier will be propagated within the communication network. A certain relay device receives a hello packet with a relay device identifier more than once, and a loop in the communication network is detected.The relay device that detected the loop (
In this case 11) determines the link to be disconnected (in this case 1
4 link), packet relaying from the packet-switched communication network 6 to 7, and packet-switched communication 'fiM1 to 6
Stop relaying packets to.

[Problem to be solved by the invention]

In the conventional technology, as mentioned above, from the viewpoint of establishing only one communication path between the originating and receiving packet communication terminals and preventing packets from circulating within the communication network, relay devices perform complex communication and change the network configuration of the entire communication network. However, the procedure for this is complicated, and the communication route between the destination and the sending packet communication terminal is determined to be one, and this route is not necessarily the optimal route (the In the example shown in Figure 2, all communications between packet communication terminals 2 and 3 are connected via packet-switched communication networks 6, 4, 5.7, and the connection route takes a major detour). .

The purpose of the present invention is to prevent packet circulation within a communication network,
In addition, the procedure for discarding duplicate received packets is simple, and a packet identification method that optimizes the communication route between the sending packet communication terminal and the destination packet communication terminal, that is, each packet terminal, An object of the present invention is to provide a packet identification method that is performed in each packet switching device, each relay device, etc. that constitute a switched communication network.

[Means to solve the problem]

In order to achieve the above object, the present invention identifies packets using address information that can be processed by a relay device and Fe2 (frame sequence), thereby making it possible to circulate through a loop within a communication network. It is possible to identify packets and duplicate packets resulting from passing through multiple routes, and discard them.

[Effect]

According to the present invention, each relay device retains the address information and Fe2O value of the received packet for a certain period of time, and each time a packet arrives, the address information and Fe2O value of the packet are retained.
The address information that previously held the e2O value, Fe2
Compare with the O value, and if they match, discard this packet.

If there is no match, this packet is relayed, and the address information and Fe2 value of this packet are held. −
On the other hand, the packet terminal device holds the source address information and Fe2O value for the packet addressed to itself, and compares it with those of the incoming packet. As a result of the comparison, if the packet is defeated, the packet is discarded. If there is no match, this packet is received and the source address information and Fe
Holds 2O value.

As described above, the present invention can realize the identification of circulating packets and the identification of duplicate packets that have passed through multiple routes by simple comparison processing, and can realize the identification of packets that are circulating through a simple comparison process and the identification of duplicate packets that have passed through multiple routes.
This method has the advantage of not requiring communication, and can be applied to the packet format realized by conventional technology without adding new information.

[Embodiment] FIG. 1 is a block diagram showing a packet-switched communication network connection method as an embodiment of the present invention, and explains a method for preventing circulation of packets in a communication network and a method for preventing duplicate packets. It is.

In FIG. 1, 15, 1.6.17 indicate packet communication terminals, 1B, 19.20 and 21 indicate packet switching communication networks, and 22.23.24 and 25 indicate relay devices. In FIG. 1, 16 indicates a packet communication terminal as a source, and 17 indicates a packet communication terminal as a destination. Also 2
6 (dotted line route) and 27 (-dotted chain line route) indicate two routes from the source packet communication terminal 16 to the destination packet communication terminal 17.

Furthermore, in the figure, since two packets that have passed through two routes are received at almost the same time by relay devices 24 and 25, relay device 24 receives a packet of route 826 and relays it to packet-switched communication network 2I. After that, a state in which a packet on route 27 is being received is shown. Similarly, the relay device 25 receives a packet on a route 27, relays it to the packet-switched communication network 21, and then receives a packet on a route 26.

This indicates that the relay devices 24 and 25 are receiving two packets that have passed through two routes in duplicate. Furthermore, duplicate packets arriving via two routes are shown arriving at the packet communication terminal 17.

A detailed explanation will be given below according to the figures.

The source packet communication terminal 16 calculates the address information and Fe2 in the packet to the destination packet communication terminal 17, sets the values, and transmits the packet to the packet switched communication y420. Relay devices 23 and 25 compare the address information and Fe2O value of the packet with information held by themselves, and if they do not match, relay the information and send it to packet-switched communication networks 18 and 21, respectively. At the same time, the address information and Fe2O value of the packet are held.

Similarly, the packet that has passed through the route 26 arrives via the relay device 2224 to the packet switching type communication network 21 to which the destination packet communication terminal 17 is connected. The packet that has passed through the route 26 also arrives at the relay device 25 . At this time, relay device 2
5 compares the address information and Fe2O value of this packet with the information it owns, but since it has previously received the packet that left route 27, there is some match in the information it holds. . When detecting that the address information and the Fe2O value match, the relay device 25 discards the packet and does not relay it to the packet-switched communication network 20.

On the other hand, the relay device 24 receives packets via the routes 26 and 27 from the packet switching communication network 19 and from the packet switching communication network y421, respectively. This figure shows the packet on route 26 arriving first, and as in the case of the relay device 25, the packet on route 27 is discarded and not relayed to the packet-switched communication network 19.

The destination packet communication terminal 17 also receives duplicate packets via two routes, but similarly to the above, it compares the address information and the Fe2O value and discards the packet that arrived later.

As mentioned above, address information, Fe
By detecting and discarding duplicate packets using
Even if a physical loop exists in the communication network, it is possible to prevent packets from circulating, and it is also possible to detect and discard duplicate packets arriving via multiple routes. Furthermore, in this case, the packet that arrives earliest among multiple routes becomes the valid packet, so packet transfer can be realized taking into consideration the traffic situation and the physical positional relationship of the source and destination packet communication terminals.

〔Effect of the invention〕

As described above, the present invention can be applied to a communication network in which a plurality of packet-switched communication networks are interconnected in a complex manner without adding new information to the packet format realized by the prior art. Furthermore, the present invention eliminates the need to reconfigure the configuration of the communication network through complicated processing and compulsion as described in the prior art, and allows the relay device to perform simple comparison processing to eliminate loops that occur within the communication network and through multiple routes. It is possible to respond by identifying and discarding duplicate packets that occur due to traffic congestion, which has the effect of reducing the processing required at the relay device, and also automatically selects the optimal route between the incoming and outgoing packet communication terminals, improving communication network communication. It has the effect of improving

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional packet identification method. Explanation of symbols 15-17...Packet communication terminal, 18-21...
Packet-switched communication network, 22-25...relay device, 2
6, 27...Route.

Claims (1)

[Scope of Claims] 1) In a communication network consisting of a packet-switched communication network that interconnects a plurality of packet-switched communication terminals, and a relay device that connects the packet-switched communication networks, each packet terminal, Each packet switching device and each relay device that make up a packet-switched communication network, when receiving a packet, uses the address information set in the packet and the address information set in the packet to detect packet transmission errors. By extracting the value of the frame check sequence (FCS), storing and comparing it with that of the previously received packet, it is possible to identify whether or not the received packet has been received repeatedly, and if there is, the corresponding packet A packet identification method characterized by discarding.