Spanning tree with rapid propagation of topology changes

For a network comprising a plurality of local area network LAN segments interconnected by a plurality of protocol entities;

• a protocol entity 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 based on configuration information stored in the protocol entity, where the topology management resources comprise:
• logic to compute configuration information in response to acceptance of configuration messages, the configuration information including an identification of a protocol entity in the network as a root of the network, an identification of a port in the plurality of ports for a root port role to be used for a preferred path to the root, and an identification of one more ports in the plurality of ports for designated port roles to be used for preferred paths between the root and respective LAN segments in the pluraliy of LAN segments coupled to the one or more ports;
• logic to compute states for ports in the plurlity of ports in response to the parameters, including placing the port providing the root port role in a forwarding state, placing the one or more ports providing the designated port roles in a forwarding state, and placing other ports in a blocking state;
• logic to accept configuration messages carrying topology information on a particular port, when the configuration message is received from a port on another protocol entity identified as the designated port for the particular port,
• wherein configuration messages include a time interval parameter indicating a time interval, and including a timer for ports in the plurality of ports indicating elapsed time from receiving of a configuration message on a particular port in the plurality of ports, and logic to expire and recompute the configuration information for the plurality of ports in the time indicating that the elapsed time reaches a value equal to a function of the time interval parameter in a received configuration message.

For a network comprising a plurality of local area network LAN segments interconnected by a plurality of protocol entity comprising:

• a plurality of ports coupled to LAN segments in the network;
• togology management resources which manage the plurality of ports according to a spanning tree algorithm, to set an active togology for the plurality of ports based on configuration information stored in the protocol entity, wherein the topology management resources comprise:
• logic to compute configuration information in response to acceptance of configuration messages, the configuration information including an identification of a protocol entity in the network as a root of the network, an identification of a port in the plurality of ports for a root port role to be used for a preferred path to the root, and an identification of one or more ports in the plurality of ports for designated port roles to be used for preferred paths between the root and respective LAN segments in the plurality of LAN segments coupled to the one or more ports;
• logic to compute states for ports in the plurality of ports in response to the parameters, including placing the port providing the root port role in a forwarding state, placing the one or more ports providing the designated port roles in aforwarding state, and placing other ports in a blocking state;
• logic to accept configuration messages carrying topology information on a particular port, when the configuration message is received from a port on another protocol entity identified as the designated port for the particular port;
• and
• resources to propagate a configuration message in response to a change in the configuration information on ports in the plurality of ports which were in the designated port role prior to the change for use by protocol entities between the port in the designated port role and leaves of the tree prior to the change.

For a network comprising a plurality of local area network LAN segments interconnected by a plurality of protocol entities, a protocol entity comprising:

• a plurality of ports coupled to LAN segments in the network;
• topology management resources which manages the plurality of ports according to a spanning tree algorithm to set an active topology for the plurality or ports based on configuration information stored in the protocol entity, wherein the tolpology management resources comprise:
• logic to compute configuration information in response to acceptance of configuration messages, the configuration information including an identification of a protocol entity in the network as a root of the network, an identification of a port in the plurality of ports for root port role to be used for a preferred path to root, and an identification of one or more ports in the plurality of ports for designated port roles to be used for preferred paths between the root and respective LAN segments in the plurality of LAN segments coupled to the one or more ports;
• logic to compute states for ports in the plurality of ports in response to the parameters, including placing the port providing the root port role in a forwarding state, placing the one or more ports providing the designated port roles in a forwarding state, and placing other ports in a blocking state;
• logic to accept configuration message carrying topology information on a particular port, when the configuration message is received from a port on another protocol entity identified as the designated port for the particular port;
• and
• logic to expire and recompute the configuration information for the plurality of ports in response to
• detection of failure of a link coupled to a particular port in the plurality of ports, if the particular port is in the root port role,
• receiving a configuration message on a particular port in the plurality of ports, having a maximum age parameter, and a message age parameter, and in which the message age parameter is at least one of equal to and greater than the maximum age parameter,
• in response to the timer indicating that elapsed time from receiving configuration message reaches a value equal to a function of time interval parameter in the received configuration message, if the particular port is in the root port role;
• resources to propagate a configuration message including the time interval parameter on a port in the designated port role periodically within a time interval indicated by the time interval parameter;
• and
• resources to propagate a configuration message in response to a change in the configuration information on ports in the plurality of ports
• which were in the designated port role prior to the change,
• caused by a configuration message received on a port in the root port role either before or after the change, on ports in the plurality of ports which are in the designated port role after the change, and
• on all ports in the plurality of ports, if the device identifies itself as the root of the network after the change.