| 摘要 |
Only one point to multipoint virtual circuit (p2mp VC) is used within a router to handle all of the sources for a particular multicast group when other particulars of the multicast group are identical within that router. The router receiving a multicast packet for a particular multicast group identifies the source and the group number by reading fields of the incoming packet, identifies the input port of the router, and identifies the output port list. The input port of the router, the group number G, and the output port list are used by the router in establishing and identifying a point to multipoint VC within the router. The invention identifies all packets arriving at that particular input port, having the same multicast group number G, and having the same output port list, and transfers them to the identified VC. The VC is associated in the routing table with the output list of ports from which copies of the multicast packet are transmitted. Accordingly, only one VC is needed to transfer packets arising from any source of the multicast group so long as the multicast packets arrive on the same port of the router and have the same output port list.
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