Importance

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Abstract

A method and apparatus for controlling multicast group subscriptions in a multicast distribution circuit is presented. When a router included in the multicast circuit receives notification to terminate support of a particular multicast group (group leave request), data flow with respect to that multicast group is initially maintained on the communication link coupling the router to the hosts. Queries are issued to hosts on the communication link to determine whether continued support of the particular group is desired by any hosts coupled to the communication link. If, while waiting for a positive response to the queries issued, a request to join an additional multicast group is received, bandwidth availability on the communication link is examined to determine if adequate bandwidth is available for supporting the newly requested group addition. If adequate bandwidth is available, the newly requested group is added to those groups supported on the communication link. However, if adequate bandwidth for support of the newly requested group is not available, one or more groups that are pending termination (group specific queries have been issued for these groups) are selected for early termination in order to make enough bandwidth available to support the newly requested group addition. The selection criteria utilized to determine the groups to be terminated may be based on a variety of parameters.

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First Claim