FAILURE RECOVERY METHOD AND NODE, AND NETWORK

Abstract

The invention comprises emergency call management apparatus (31) and a mobile station (1). The emergency call management apparatus (31) monitors the emergency call generation rate, which is indicative of the rate of generation of emergency calls in a network, and on the basis of the result of this monitoring, transmits state information indicative of the restriction state of communication in that network, when the emergency call generation rate attains a preset condition. The mobile station (1) has emergency number information indicative of a number to be dialed to make an emergency call, and transmits, on the basis of the emergency number information and the received state information, a connection request to the network when the restriction state is a state in which only that emergency call is accepted and the number that has been dialed is the number to be dialed to make that emergency call. This provides a higher probability that an emergency call will be processed in situations in which there is a high rate of generation of emergency calls. This is because in such situations the network only has to process emergency calls.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 shows where a routing protocol is implemented in a node;

FIG. 2 is a functional block diagram of a node;

FIG. 3 is a flowchart showing an existing algorithm;

FIG. 4 is a flowchart showing the processing procedure of a failure recovery method;

FIG. 5 is a flowchart showing the procedure of process 1;

FIG. 6 is a flowchart showing the procedure of process 2;

FIG. 7 shows the configuration of a tree notification packet;

FIG. 8 shows the configuration of a failure notification packet;

FIG. 9 shows an exemplary network for illustrating the failure recovery method;

FIG. 10 a to FIG. 10f illustrate link-sharing nodes;

FIG. 11 a to FIG. 11g illustrate the failure recovery method;

FIG. 12 a to FIG. 12g illustrate the failure recovery method;

FIG. 13 shows table 1 (link-sharing nodes); and

FIG. 14 shows table 2 (notification packet destination nodes in the event of link failure).

Claims

1. A failure recovery method in a node in a network, comprising the steps of: ascertaining tree information of the network by acquiring the tree information from another node or computing the tree information;extracting in advance a node set as a range affected by link failure, based on the ascertained tree information, the node set including incoming and outgoing links of the node as part of a tree;notifying, when link failure is detected, only the affected area that link failure has been detected; andrecomputing a path when link failure is detected by the node or when the notification is received from another node.

2. The failure recovery method according to claim 1, wherein the path recomputation is performed assuming that failure occurred simultaneously on an outgoing link paired with an incoming link whose failure has been detected.

3. The failure recovery method according to claim 1, wherein the notification is performed by specifying a path in advance.

4. Anode in a network, comprising: tree information managing means for ascertaining tree information of the network by acquiring the tree information from another node or computing the tree information;link-sharing node extracting means for extracting in advance a node set as a range affected by link failure, based on the tree information ascertained by the tree information managing means, the node set including incoming and outgoing links of the node as part of a tree;failure notifying means for notifying, when link failure is detected, only the affected area that link failure has been detected; andpath recomputing means for recomputing a path when link failure is detected by the node or when the notification is received from another node.

5. The node according to claim 4, wherein the path recomputing means performs the path recomputation assuming that failure occurred simultaneously on an outgoing link paired with an incoming link whose failure has been detected.

6. The node according to claim 4, wherein the failure notifying means performs the notification by specifying a path in advance.

7. A network constituted by a node as claimed in claim 4.

8. A computer program that causes a general-purpose information processing apparatus to realize functions corresponding to a node as claimed in claim 4, by being installed on the information processing apparatus.