3com Corporation

Raphael J Weyman

Maurice A Goodfellow

Francisco Aquino

Jane Riegel

Jacek A Tulacz

David Reinauer

A distributed router composed of individual units connected by links in a routing fabric which appears to be a single network entity routes multicast packets by bridging to the final unit in the fabric. At the final unit the packet is replicated as necessary and routed. The scheme avoids multiple transmission of the same packet across the fabric.

System and method for distributed multicast routing

A network unit for use in a distributed bridging fabric has a multiplicity of user ports for the transmission of data frames to and from an external network and at least one fabric port for the transmission of frames between the network unit and another unit in the fabric. The network unit has a forwarding database for containing entries each including a media access control address, and a lookup engine organized for the insertion of an entry into the forwarding database when the network unit receives a data packet at a user port. The unit broadcasts via each fabric port of an 'address added' message identifying a respective media access control address. The lookup engine also responds to such an 'address added' message received from another unit to make a corresponding entry in the database and to annotate an entry to indicate activity of an address in response to an address which is already in the database. The network unit has an aging engine organized for the polling of entries in the database. The aging engine refreshes an entry for which the respective media access control address is annotated as active and is organized for the selective removal of inactive entries from the database.

Distributed bridging with synchronization forwarding databases

A network unit comprises a multiplicity of ports for transmitting and receiving data packets, a bridging facility and a routing facility. The network unit has a multiplicity of mutually exclusive states which includes an initial state from which said network unit can transition to either a slave state; or a waiting state from which in the absence of receipt from elsewhere of a broadcast advertisement including an advertised address corresponding to an address of the unit, the unit transitions to a master routing state in which the routing facility is enabled and the unit broadcasts a corresponding advertisement including an address of the unit. The unit transitions from the waiting state, when it receives from elsewhere (i.e., another unit) such a broadcast advertisement, to a master bridging state in which the routing facility is disabled and the unit provides commands for disabling a routing facility of other similar units to which the network is connected. The states include a slave routing state, in which the routing facility is enabled, and a slave bridging state, in which the routing facility is disabled. In the slave states the advertisements are not broadcast and the unit responds to routing enabling and disabling commands from a unit in a master state. The scheme provides in conjunction with external connectivity resilience in the event of a cascade failure.

Stackable network units with resiliency facility

A cascaded stack of routing units each of which routes packets that it receives at its external ports and which conduct an election for a lead router that lends network and media access control addresses to the router interfaces of the other units in the stack. These other subordinate units have selected ancillary functions suppressed but otherwise have full routing capability. A packet entering the stack and requiring routing is routed by the unit that receives it and is thereafter bridged to its egress port.

Growing community of inventors

Hemel Hempstead, United Kingdom

Raphael J Weyman