| 摘要 |
<p>PROBLEM TO BE SOLVED: To secure proper communication channels and use route resources efficiently so as to carry out a relay switching operation by giving a unit number which can be identified on the same network to each unit. SOLUTION: An opposed unit 1b that has received a call set message for an opposed unit 1c from a relay switching unit 1a retrieves a channel to the opposed unit 1c by a route retrieving unit 11. If a first route is in trouble, the call set message is transmitted through a route to the relay switching unit 1a that serves as a second route. The relay switching unit 1a which has received the call set message recognizes that an abnormal route is selected for the call set message by finding out its one unit number is user/user information elements contained in the call set message. At this point, in a case in which an abnormal route is found that relay processing is successively carried out, a release message is transmitted so as to carry out a release processing operation, and an optimal route is selected through route selection processing. By this setup, route resources can be effectively utilized.</p> |
