Patent ID: 6262977
Filing Date: 2001-07-17
Classification: H04L

Abstract:
For a network comprising a plurality of local area network LAN segments, a network device comprising:a plurality of ports coupled to LAN segments in the network;topology management resources which manage the plurality of ports according to a spanning tree algorithm, to set an active topology for the plurality of ports, includingmemory storing parameters for specifying the active topology, the parameters including information for an identification of a root of the network, identification of a port in the plurality of ports for a root port role to be used for a path to the root, identification of one or more ports in the plurality of ports for designated port roles to be used for paths between the root and respective LAN segments coupled to the one or more ports, identification of one or more ports in the plurality of ports for alternate port roles, and identification of one or more ports for alternate port roles also having backup roles;logic to compute and implement states for ports in the plurality of ports in response to the parameters, including placing the port in the root port role in a forwarding state, placing the one or more ports in the designated port roles in the forwarding state, and placing the one or more ports in the alternate port roles in a blocking state; andlogic to manage transition of the states of the ports in the plurality of ports in response to a change in the active topology, includingfor a port coupled to one of the plurality of LAN segments, changing from the alternate port role in the backup role to a designated port role, causing transition from the blocking state to a transitional state, and then upon satisfaction of a condition of the transitional state, and upon a designated port connected to the same one of the plurality of LAN segments transitioning to the blocking state, causing transition to the forwarding state,for a particular port changing from the alternate port role to the root port role, causing transition from the blocking state to the forwarding state without requiring satisfaction of the condition of the transitional state.