The port states and roles are decoupled to make faster & more intelligent decisions on topology. The neighboring bridges interact with each other using BPDUs instead of just passing the root bridge BPDU. A proposal/agreement mechanism which doesnt depend on any timers, is used to converge the topology, in a very fast manner.
Port Roles
Root Port
Designated
Alternate
Backup
Port States
Blocking (discarding)
Learning
Forwarding
Port Types
Edge Port (connected to a host, Portfast)
P2P (full-duplex connection to another bridge)
Shared (half-duplex)
New BPDU stuff
BPDUs are sent every 3 seconds by every bridge.
If 3 BPDU packets in a row are not heard from a neighbor, he is down.
Additions to the BPDU
Role&State of originating port.
Handles proposal / agreement mechanism
RSTP BDPU are version 2
References:
Understanding Rapid Spanning Tree Protocol (802.1w) @ Cisco
Cisco AVVID Network Infrastructure: Implementing 802.1w and 802.1s in Campus Networks Implementation Guide
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