3com Corporation

Hewlett-packard Company

Jacek A Tulacz

Jane Riegel

Kin Moon Leung

John M Livingston

Francisco Aquino

Raphael J Weyman

David Reinauer

A stack of network routers is composed of at least one (elected) master unit and one or more slave units each capable of running a routing protocol. Only the master unit runs the entire routing protocol at a given time. It forwards direct update messages via a transmission control protocol to each of the slave units. These direct update messages may include specific packet formats for the protocol state machinery where such machinery is required by the routing protocol, e.g., the interface state machine and the neighbor state machine for the OSPF protocol, and for the net databases, e.g. the link state databases for the OSPF protocol, in each of the slave units. Each slave unit may run its protocol state machinery (where provided) based purely on the direct update messages received from the master. The synchronisation of the net databases may be based on snooping net update packets and a comparison of the information received thereby with verification data messages sent from the master unit. The synchronization allows the running of the routing protocol on multiple physical routers in a stack without requiring the overhead of a back-up unit that would not perform routing unless a master router unit became unavailable.

Stackable routers employing a routing protocol

A stack of network routers is composed of at least one (elected) master unit and one or more slave units each capable of running a routing protocol. Only the master unit runs the entire routing protocol at a given time. It forwards direct update messages via a transmission control protocol to each of the slave units. These direct update messages may include specific packet formats for the protocol state machinery where such machinery is required by the routing protocol, e.g. the interface state machine and the neighbor state machine for the OSPF protocol, and for the net databases, e.g. the link state databases for the OSPF protocol, in each of the slave units. Each slave unit may run its protocol state machinery (where provided) based purely on the direct update messages received from the master. The synchronization of the net databases may be based on snooping net update packets and a comparison of the information received thereby with verification data messages sent from the master unit. The synchronization allows the running of the routing protocol on multiple physical routers in a stack without requiring the overhead of a back-up unit that would not perform routing unless a master router unit became unavailable.

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.

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Marlborough, MA, United States of America

Jacek A Tulacz