spanning-tree never tires me...

rstp (802.1w) introduced new port roles; among them, discarding.  discarding replaces the
traditional roles of disabled, blocking and listening, leaving only discarding, learning
and forwarding.  discarding is in the active topology as a replacement during the
listening phase of spanning tree but still does not populate mac addresses, just as
listening doesn't in STP. so although discarding has replaced listening, discarding during
the listening phase is considered part of the active topology. this is kind of a silly point because ultimately the role is called discarding yet part of the active topology.  go fish. i guess it's actively discarding...

again, rstp only defines a discarding state from disabled through listening.

alternate and blocked ports in rstp:
An alternate port receives more useful BPDUs from another bridge and is a port blocked.

A backup port receives more useful BPDUs from the same bridge it is on and is a port
blocked.

a port blocked here is important, as opposed to a blocked port.  there are no blocked ports in rstp.

i didn't make this shit up...