Patent ID: 6243758
Filing Date: 2001-06-05
Classification: H04L,H04W

Abstract:
A computer network comprising:a plurality of subnetworks each comprising a plurality of interconnected hosts, said subnetworks forming a multicast scope which defines a reachable extent of multicast packets and said hosts forming at least one multicast group within said multicast scope;a plurality of routers interconnecting said subnetworks and further connecting said subnetworks to an external subnetwork;each of the hosts transmitting a multicast packet containing a scope field indicating that transmission of the multicast packet beyond the scope is forbidden and a flag indicating whether only hosts within the scope are allowed to participate in a group activity or mobile hosts outside the scope are also allowed to participate in the group activity;each of said routers, on receiving a multicast packet, preventing the received packet from being transmitted beyond said scope if said scope field is contained in the received packet;a home agent within said scope;a foreign agent within said external subnetwork for acquiring home location of a mobile host visiting the external subnetwork and informing said home agent of current location of the visiting mobile host and address of the foreign agent; andsaid home agent, on receiving said multicast packet, encapsulating the received packet in a payload field of a packet and transmitting the packet to said foreign agent if the flag of the inulticast packet indicates that participation of mobile hosts outside the scope in the group activity is allowed,said foreign agent, on receiving said packet from the home agent, forwarding the payload of the received packet to the visiting mobile host;wherein said multicast packet further contains a subnet flag indicating whether only hosts attached to one of the subnetworis within the scope are allowed to participate in a group activity or mobile hosts outside the subnetwork are also allowed to participate in the particular group activity, andwherein a mobile host of said external subnetwork is arranged to:receive said multicast packet when visiting one of said subnetworks within said scope, andread contents of the received multicast packet if the flag of the received multicast packet indicates that participation of outside mobile host in a group activity is allowed.