Optimal sync for rapid spanning tree protocol

An intermediate network device configured to forward network messages within a bridged network, the device having a plurality of ports for connecting the device to one or more network entities, the intermediate network device comprising:

• a port role selection state machine configured to assign roles to the ports;
• a port transition state machine configured to transition the ports among a plurality of spanning tree protocol (STP) states depending on the assigned roles;
• and
• a sync manager for use in executing the STP, wherein,
• the port role selection state machine and the port transition state machine cooperate so as to assign one of the device's ports to a Root Port Role, to assign one or more of the device's ports to an Alternate Port Role, and to assign one or more of the device's ports to a Designated Port Role,
• the port role selection state machine and the port transition state machine further cooperating to transition the ports assigned to the Root Port Role and the Designated Port Role to a forwarding STP state and to transition the one or more ports assigned to the Alternate port role to a discarding STP state, and
• in response to receiving a bridge protocol data unit (BPDU) message having a proposal flag that is asserted, the sync manager cooperates with the port transition state machine to leave one or more of the ports assigned to the Designated Port Role in the forwarding STP state, provided that the BPDU message was received on the port assigned the Root Port Role and further provided that the one or more ports assigned to the Alternate Port Role are in a discarding STP state.

In an intermediate network device having a plurality of ports for forwarding network messages within a bridged network, a method for efficiently transitioning the ports among a plurality of spanning tree protocol (STP) states, the method comprising the steps of:

• executing the STP at the intermediate network device so as to elect a root of the bridged network, to designate a port of the device to be the current root port and to assign one or more of the device's ports to a Designated Port Role;
• transitioning the ports assigned to the Designated Port Role to a forwarding STP state;
• receiving a bridge protocol data unit (BPDU) message, the BPDU message having a proposal flag that is asserted;
• and
• if the proposal-BPDU message was received on the current root port, leaving the one or more ports assigned to the Designated Port Role in the forwarding STP state.