Electrical computers and digital processing systems: multicomput – Computer-to-computer data routing
Reexamination Certificate
1998-07-31
2001-01-30
Maung, Zarni (Department: 2758)
Electrical computers and digital processing systems: multicomput
Computer-to-computer data routing
C709S217000, C709S221000, C370S902000
Reexamination Certificate
active
06182147
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to multicast packet routing.
2. Related Art
In a computer network, it is often desirable to transmit messages from a single source to a selected plurality of destinations. This activity is often referred to as “multicast routing.” It is further desirable for the plurality of destinations to be capable of self-selection, so as to add themselves to, or to take themselves off, multicast distribution groups.
One method in the known art is the IGMP (Internet Group Management Protocol), in which messages are transmitted from a single source to a plurality of destinations, and in which destination devices can add themselves to, or take themselves off, multicast distribution groups. One problem with IGMP is that it uses bi-directional communication between routing devices (that receive messages from the source device) and the destination devices, so that routing devices intermediate between the source and destinations can determine how to route multicast messages. IGMP is not well suited when a primary communication path between the source and the destinations is unidirectional, such as in distribution systems using satellite communication.
Accordingly, it would be desirable to provide a method and system for multicast group routing using unidirectional links. This advantage is achieved in an embodiment of the invention in which a set of uplink routers and a set of downlink routers provide a unidirectional distribution path from a set of sources to a set of destinations, and in which some (but not all) downlink routers act as proxies for others to inform uplink routers whether distribution should occur over that unidirectional distribution path.
SUMMARY OF THE INVENTION
The invention provides a method and system for multicast group routing using unidirectional links. A set of uplink routers and a set of downlink routers provide a primary unidirectional distribution path from a set of sources to a set of destinations. A relatively smaller reverse communication channel is provided between the destinations and the sources. When a destination desires to add itself to, or take itself off, a multicast distribution group, one of the downlink routers acts as a proxy for that destination and so informs the relevant source. The selection of the proxy does not require bi-directional communication between either uplink routers or downlink routers.
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Cesari and McKenna LLP
Cisco Technology Inc.
Dinh Khanh Quang
Maung Zarni
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