Cisco Technology, Inc.

Alex Tweedly

Dino Farinacci

Mike Shand

Joel P Bion

Bruce Albert Thompson

A data structure is stored in a memory of a router, the router located along a path between a source end station and a plurality of destination end stations in a multicast distribution tree. In response to receipt of trace packets containing a listing of network devices in the multicast distribution tree, the data structure is updated. When the source end station desires to send a multicast packet, it transmits a packet to the router. The router then writes the path information stored in the data structure into the packet. Such path information may include a tree list that specifies the arrangement of network devices along the multicast distribution tree and an address list that specifies the Internet Protocol (IP) addresses of these network devices along the multicast distribution tree. By storing the complete description of the network devices of the multicast distribution tree in the packet, routing demands on the devices along the multicast path are minimized.

Small group multicast in a computer network

A network packet is encapsulated and has at least one field in the header of the encapsulation. A multicast delivery tree is written into a field of the encapsulating header. A method for operating a router to use the multicast delivery tree encapsulated in the header of the network packet has the following steps. The router receives a packet from a computer network, the packet having an encapsulated field. The router then reads a multicast delivery tree from the encapsulated field, the multicast delivery tree having a route to each of a plurality of destination stations. Then, the router forwards the packet to an address selected in response to the multicast delivery tree.

A method for transporting real-time data such as voice over a packet-based infrastructure, and a switch for use with that method, are disclosed. In this method, datagrams from multiple data streams are packaged in a single tunnel packet for transport across a network to an intermediate switching point (switch). To reduce bandwidth, each datagram in the tunnel packet (e.g., tunneled datagram) can be sent in a compressed-header format identified by a context identifier (CID) for its data stream. The switch saves context state for each tunnel and CID it is receiving packets for. The switch deaggregates received tunnel packets into tunneled datagrams and associates each datagram with its context state. Based on the destination indicated in its context state, each datagram it re-aggregated in an outgoing tunnel packet bound for a next switch or the destination endpoint itself.

Tunneled datagram switching

The invention solves the problem of overloading intermediate routers with state information as the number of multicast groups increases to millions of groups. The invention places multicast delivery tree information in the header of an encapsulated multicast packet, thereby relieving the routers from maintaining any state information about the multicast groups. The encapsulated packet is referred to as a small group multicast packet, or SGM packet. Routers which are neither branch points of the delivery tree nor destination routers will also need to do no additional forwarding processing other than that needed for standard unicast forwarding. A protocol designation field in the Layer 3 header informs the router that the packet is a SGM packet, and that the router is therefore instructed to parse the packet for route information. The router parses the SGM packet header and determines the next hop address of routers in the multicast delivery tree. The standard unicast forwarding tables are then consulted to determine the next packet destination addresses, and the router then rewrites the SGM packet and routes it to the next hop router. The routing tables also instruct the router as to which outbound port to route the packet.

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Argyll, United Kingdom

Alex Tweedly