The STP algorithm has two arguments, being the first one the bridge identifier sending the BPDU and the second one the bridge identifier receiving it.
n-1] where d is any BPDU sent out of any given channel or received from any given channel.
2] will know about it thanks to the BPDU exchange with its neighbor [B.
i, j] = 0, so those ports will not be sending any BPDU any longer and the corresponding terms will be cancelled from the resulting equation as they will not make any communication possible.
From then on, this is the resulting equation for BPDU exchange
It may be appreciated that BPDU communication is now unidirectional and will remain that way as long as all bridges within the topology are on or their parameters are not modified.
Port Role Value Send/Receive BPDU Associated State Designated 0 SEND Forwarding Root 1 RECEIVE Forwarding Non-Designate 3 RECEIVE Blocking TABLE III.
On one hand, the former consists of device-generated frames required for the proper operation of a network, named BPDUs, an acronym standing for Bridge Protocol Data Unit, providing the path that the latter must follow.
Regarding control-plane traffic, every link joining two bridges within a loop must have an end whose role is to be a Designated Port, which is the one sending BPDUs, whereas the other end may have a role as either a Root Port or a Non-Designated Port, which is the one receiving BPDUs.