| 摘要 |
<p>PROBLEM TO BE SOLVED: To set an optimum preliminary route in accordance with a situation at that time by providing a means for listing up plural preliminary route candidates corresponding to one present route and selecting one of the plural preliminary route candidates when the present route breaks down. SOLUTION: When the fault occurs in the present route, the preliminary route is retrieved one by one in accordance with a preliminary route candidate management table. When the preliminary route where the band of the present route or more can be secured exists, it is selected. When it does not exist, the other routes are retrieved. When the route does not exist even if all the candidates are retrieved, it is considered whether the band of the present route can be distributed or not by using the plural preliminary routes. When it can be distributed, the plural candidates are selected. When it cannot be distributed, a selection impossible notice is given to a local area network 2-1. When the preliminary routes can be selected by plural ways, the way by which a distance between local area networks 2-1 and 2-2 becomes the shortest is selected.</p> |
