JPS62281541A - Routing control system - Google Patents

Abstract

PURPOSE:To avoid the ping-pong looping by allowing each station to apply route retrieval and by passing other path in response to the state at a relay station. CONSTITUTION:Each node the decides packet type to a reception packet at first. Priority is given to a path receiving the packet in the order of reception of the route retrieval packet and a route retrieval packet is sent simultaneously to all paths except the received path. The packets whose reception order is a 2nd and succeeding order are abolished. When the packet type is an even notice packet and it is addressed to other station, the packet is sent simultaneously to all paths except the received path and when the packet is addressed to its own station, a new route is retrieved. If ping-pong and looping take place due to bypassing, the occurrence of an event is informed to the station being the destination of the packet and the said station applies new routing, then the routing table is rewritten.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a routing control method for a packet switching network, and in particular to an adaptive routing method that enables detours in the event of a failure or abnormal load. Regarding.

[Conventional technology]

The route search method using broadcasting is to create a sequence of nodes to be passed while sequentially recording relay node addresses in route search packets, and the station receiving the route search packet sends the sequence of nodes to the originating station as a response. A method is known for determining the route from a station to a destination station.

A similar method of this type is 1, for example, ``Source Routing of Frames in a Multiple Segment Network''.
ting of [”ra+aes in a Mul
tiplC-5egment Network) J
Raised p) Rero.

[Problem that the invention attempts to solve]

However, when performing routing according to the routing information obtained through the route search as described above, the originating station adds a string of nodes passed to the destination station as a packet header, and the relay station sends out the packet according to the node string in the packet header. Therefore, when a relay station is damaged or under abnormal load, a detour to the other route is not possible, resulting in packet loss and increased delay time.

In addition, in the fixed detour method, in which the priority order for detouring is set in a fixed table in advance, when a packet is detoured to the other route due to a failure, etc., there is a ping-pong phenomenon in which packets go back and forth between two exchanges, and a packet is sent back and forth between two exchanges. Since a circular looping phenomenon occurs and the priority order is fixed, there is a problem that the above-mentioned phenomenon cannot be avoided.

The purpose of the present invention is to solve the above problems, enable a detour to another route depending on the situation at the middle #A station, avoid the ping-pong looping phenomenon caused by the detour, and communicate with the destination station. The object of the present invention is to provide a routing control method that allows routing to be performed as long as there is a route between them.

[Means for solving the problem] When transmitting a route search packet by circulation, each node broadcasts the route search packet that arrived first to all routes including the strategy that received the route search packet. ,
Each node receives the same route search packet once from all routes to the node. For this reason, each node monitors all routes to its own station, and prioritizes each strategy in the order of arrival of multiple route search packets that are circulated by the same route search. It is possible to obtain the sending priority order for all routes when the destination is the station that sent the packet.

[Effect]

By each station searching for route 1 as described above, each station can obtain the priority order of the sending route when that station is the destination with respect to all other nodes, and depending on the situation at the relay station. Detours can be made in other directions accordingly.

Also, if the packet does not arrive at the destination station due to detour,
If the destination station becomes aware of the situation, it searches for the route again.
This can be dealt with by rewriting the routing table, so the station that detects the situation can notify the destination station by circular, thereby avoiding the ping-pong looping phenomenon caused by the detour, and reducing the distance between the station and the destination station. Routing is possible as long as a route exists.

[Embodiments of the invention]

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

The 21st line is a system configuration diagram of a packet switching network,
A plurality of packet exchanges 1 to 4 are interconnected by relay lines, and each exchange can be connected to packet type terminals 5, 6, a multiplex representative [7, or another packet switching network 8, etc.].

FIG. 1 is a diagram showing the operation of each node in this embodiment. Each node first determines the packet type of the received packet. For route search packets, priority is given to the strategy that received the packet in the order in which the packet was received, and for the first arriving packet, the route search packet is routed to all strategies except for the receiving route. Younger packets that are received second or later are discarded. If the packet type is an event notification packet, if it is addressed to another station, it will be broadcast and relayed to all routes other than the receiving route, and if it is addressed to the own station, a new route search will be performed. For data packets other than those listed above, the number of relays is checked, and if the received packet does not arrive at the destination station even after exceeding the preset maximum number of relays, the received packet is discarded.

An event notification packet indicating that the number of relays has exceeded by an event code is transmitted to the packet originating station by broadcasting. Data packets that have not exceeded the relay count are considered to have been relayed normally, are relayed using the routing table, and the relay count is updated.

FIG. 3 is a diagram modeling the exchange and trunk line in FIG. 1. Symbols a...j are strategy numbers for identifying outgoing lines of each node.

4th I%1~1~ is a diagram showing the broadcasting of route search packets and the assignment of priorities at each node in the first embodiment. Hereinafter, a case will be described in which, for example, node A performs a route search.

Node A adds to route search packets 9 and 10 its own station number A and, for example, a sequence number as an identifier for other nodes to identify multiple route searches performed by the same station. It is sent to all directions of node A, that is, to node B and node C. The format of the intra-network header of the route search packet is as shown in FIG.

The destination number is set to a global address indicating the return. It goes without saying that it is also possible to use other identification information as the identifier, such as the time when node A started the route search process.

FIG. 5 is a diagram showing the reception of route search packets 9 and 10. Node B and node C receive the route search packet 9 sent by node A. ]0, give priority to each strategy in the order received.

In the figure, . . . indicates priority order.

FIG. 6 is a diagram showing broadcasting of node B and node C. Node B and node C transmit route search packets 11 to 16 to their own full routes in response to route search packets 9 and 1o that arrived first.

FIG. 7 is a diagram showing the reception of route search packets 11 to 16 broadcasted by node B and node C. Node A receives route discovery packet 11.14, but node A
has already broadcast the same route search packets 1 and 2, so route 1 to search packets 11 and 14 are discarded. Node B receives the Roumil search packet 15, and node C receives the route search packet 12, but since these are later arriving packets from different routes, priority is given to the received route and If so, a new broadcast will not be made and will be discarded. How to determine if it is a late-arriving packet.

This is done using the identifier given when sending the route search packet. Node D receives route search packets 13, 16, and it is assumed that among these, for example, route search packet 1 and 3 arrive at node D first. Node D gives priority to the received route for the route search packet 13 that arrived first, and routes route search packets 17 and 18 as shown in FIG.

For the later arriving route packet search 16, only the route priority is recorded and discarded.

FIG. 9 is a diagram showing the reception of route search packets 17 and 18. Node B receives the route search packet 17 and node C receives the route search packet 18, but since both are late arriving packets, only priority is given to the receiving route and packets 17 and 18 are discarded.

When node A searches for a route through the process described above, all other nodes, that is, node B and node C
1 and node D can obtain the priorities of the sending routes when the destination is node A for all routes of their own stations.

FIG. 10 is a diagram in which the priority order of each strategy obtained by node A searching for a route is expressed in the form of a routing table.

The above route search performed by node A is performed by node B.
, node C1, and node D, each node can obtain the priority of the transmission route with respect to all other nodes when that node is the destination station.

FIG. 11 is a diagram showing an example of a routing table completed by the above processing. Data packet relay processing is performed by referring to a routing table as shown in FIG. The format of the intra-network header of the data packet is as shown in FIG. Each node refers to the routing table based on the destination number in the header and selects a sending route. If the strategy with priority 1 is faulty or overloaded, it is sent to the route with priority 2 or ;3.

Note that in order to update the routing table in accordance with the constantly changing network conditions, the route search as described above is performed periodically.

If a ping-pong phenomenon or a looping phenomenon occurs due to sending to a route with priority order 2 or 3, the following processing is performed each time to deal with it.

As shown in FIG. 2, each node adds one time to the number of relays recorded in the packet each time it performs relay processing for data buckets 1 to 1. If the number of relays M exceeds the number of gold nodes in the network and the packet has not yet arrived at the destination station, the packet receiving station discards the received packet and sends an event message to the node that is the destination of the received packet with an event code. Send notification packets by broadcasting. The format of the intra-network header of the event notification packet is as shown in FIG. The destination number is set to the source station of the data packet for which the number of relays has been exceeded. The destination station of the event notification packet receives the event notification packet as long as a route exists between it and the originating station. The destination station for event 1 - notification bucket i is
When an event notification packet is received, a new route 1 to search packet is sent out by broadcast in order to rewrite the priority order when the local station is the destination.

- If a ping-pong phenomenon or a looping phenomenon occurs due to a detour as a result of the above processing, the station that is the destination of the packet is notified of the occurrence of Event 1-, and the station performs a new heart search to route the packet. Since the table is rewritten, it is possible to avoid ping-pong and looping phenomena.

〔Effect of the invention〕

As explained above, according to the present invention, each switching center can prioritize all routes to all destination stations, so it is possible to prevent failures and errors at relay stations. Depending on various conditions such as load, detours can be made to the next most desirable route, and even if packets do not arrive at the destination station due to detours, the route is searched again and the routing table is rewritten. This makes it possible to avoid ping-pong and looping phenomena6.

[Brief explanation of the drawing]

Figure 1 is a flowchart showing the processing procedure of each node in the packet switching network, Figure 2 is a system configuration diagram of the amount of packet exchanged, Figure 3 is a model diagram of the packet switching network, and Figures 4 to 9.
10 shows a routing table created by node A's route search; FIG. 11 shows an example of a completed routing table; FIGS. 12 to 14. The diagram shows various buckets 1
It is a diagram showing the format of the intra-network header of ~. 9-1B...Route search packet, 19-z5...
routing table.

Claims (1)

[Claims] 1. In a packet switching network, each switching station sends route search packets by broadcasting, and other switching stations prioritize each line in the order in which the route search packets arrive, and A routing control system characterized in that a route search packet destined for a source station is routed using the priority order, thereby making it possible to take a detour through each exchange. 2. In the packet switching network described in paragraph 1, if an event occurs in which a packet does not arrive at the destination station due to a detour at each switching station, although a route to the destination station exists, the switching station that detected the event broadcasts a packet with an event code to notify the destination station of the occurrence of the event, and the destination station issues a route search packet again to determine the priority of each exchange. A routing control method characterized by rewriting.