VC sharing for multicast in a computer network

A router for routing multicast packets, comprising:

• means for receiving a multicast packet by a router at an input port;
• means for reading a source end station address from the layer 3 field of said packet;
• means for reading a multicast group number from the layer 3 address of said packet;
• means for identifying an output port list in response to said source end station address and said multicast group number;
• and
• means for selecting a point to multipoint virtual circuit that is internal to said router in response to said input port, said multicast group, and said output port list.

A router for routing a multicast packet comprising:

• a line card to receive said packet and to read a field indicating that said packet is a multicast packet, and in response to a determination that said packet is a multicast packet, to read a layer 3 source address as a multicast source station, and to read a layer 3 destination address as a multicast group number;
• a first circuit to select an output port list in response to said source station and said multicast group;
• a second circuit to select a point to multipoint virtual circuit that is internal to said router for routing said packet in response to said output port list and said multicast group;
• and
• a replication mechanism to replicate said packet and to transmit said packet through ports listed in said output port list.

A computer readable media comprising:

• said computer readable media having written thereon instructions for execution on a processor for practicing a method for routing a multicast packet by a router, the method having the steps of, receiving a multicast packet by a router at an input port;
• reading a source end station address from the layer 3 field of said packet;
• reading a multicast group number from the layer 3 address of said packet;
• identifying an output port list in response to said source end station address and said multicast group number;
• and
• selecting a point to multipoint virtual circuit that is internal to said router in response to said input port, said multicast group, and said output port list.

A method for routing a multicast packet by a router, comprising:

• receiving said multicast packet by a router;
• reading a source end station address from said packet;
• reading a multicast group number from said packet;
• identifying an output port list in response to said source end station address and said multicast group number;
• and
• selecting a point to multipoint virtual circuit that is internal to said router in response to an input port, said multicast group, and said output port list, said point to multipoint virtual circuit routing the multicast packets from an input port to at least one output port.

A computer readable media comprising:

• said computer readable media having written thereon instructions for execution on a processor for practicing a method for routing a multicast packet by a router, the method having the steps of, receiving a multicast packet by a router at an input port;
• receiving a multicast packet by a router;
• reading a source end station address from said packet;
• reading a multicast group number from said packet;
• identifying an output port list in response to said source end station address and said multicast group number;
• and
• selecting a point to multipoint virtual circuit that is internal to said router in response to an input port, said multicast group, and said output port list, said point to multipoint virtual circuit routing the multicast packets from an input port to at least one output port.

A router, comprising:

• means for receiving a multicast packet by said router;
• means for reading a source end station address from said packet;
• means for reading a multicast group number from said packet;
• means for identifying an output port list in response to said source end station address and said multicast group number;
• and
• means for selecting a point to multipoint virtual circuit that is internal to said router in response to an input port, said multicast group, and said output port list, said point to multi-point virtual circuit routing the multicast packets from an input port to at least one output port.

A router, comprising:

• an I/O card to receive a multicast packet by said router;
• a processor to read a source end station address from said packet, and to read a multi-cast group number from said packet;
• and
• a CPU to identify an output port list in response to said source end station address and said multicast group number, and to select a point to multipoint virtual circuit that is internal to said router in response to an input port, said multicast group, and said output port list, said point to multipoint virtual circuit routing the multicast packets from an input port to at least one output port.

A method for routing a multicast packet by a router, comprising the steps of

• receiving the multicast packet at an input port of a line card of the router, the packet having a source end station address;
• determining an output port list for the multicast packet, the output port list including a plurality of output ports of the router on which the packet is to be forwarded;
• if there is an existing point to multipoint virtual circuit beginning at the input port of the line card and terminating at the plurality of output ports, associating the multicast packet with the existing point to multipoint virtual circuit, regardless of the multicast packet's source end station address;
• and
• if there is not an existing point to multipoint virtual circuit beginning at the input port of the line card and terminating at the plurality of output ports, creating a new point to multi-point virtual circuit and associating the multicast packet with the new point to multipoint virtual circuit.

A router for routing a multicast packet comprising

• a line card to receive a multicast packet having a source end station address;
• a first circuit configured to determine an output port list for the multicast packet, the output port list including a plurality of output ports of the router on which the packet is to be forwarded;
• and
• a second circuit configured to,
• if there is an existing point to multipoint virtual circuit beginning at the input port of the line card and terminating at the plurality of output ports, associate the multicast packet with the existing point to multipoint virtual circuit, regardless of the multicast packet's source end station address;
• and
• if there is not an existing point to multipoint virtual circuit beginning at the input port of the line card and terminating at the plurality of output ports, create a new point to multipoint virtual circuit and associate the multi-cast packet with the new point to multipoint virtual circuit.

A computer readable medium containing executable program instructions for routing a multicast packet, the executable program instructions comprising program instructions for:

• receiving the multicast packet at an input port of a line card of the router, the packet having a source end station address;
• determining an output port list for the multicast packet, the output port list including a plurality of output ports of the router on which the packet is to be forwarded;
• if there is an existing point to multipoint virtual circuit beginning at the input port of the line card and terminating at the plurality of output ports, associating the multicast packet with the existing point to multipoint virtual circuit, regardless of the multicast packet's 11 source end station address;
• and
• if there is not an existing point to multipoint virtual circuit beginning at the input port of the line card and terminating at the plurality of output ports, creating a new point to multi-point virtual circuit and associating the multicast packet with the new point to multipoint virtual circuit.