36 CHAPTER 4: USING RESILIENCE FEATURES
The protocol is a part of the IEEE Std 802.1w-2001, bridge specification.
To explain RSTP more effectively, your Switch will be referred to as a
bridge.
Rapid Spanning Tree
Protocol (RSTP)
The Rapid Spanning Tree (RSTP) is an enhanced Spanning Tree feature.
RSTP implements the Spanning Tree Algorithm and Protocol, as defined in
the IEEE Std 802.1w-2001.
Some of the benefits of RSTP are:
■ Faster determination of the Active Spanning Tree topology throughout
a bridged network.
■ Support for bridges with more than 256 ports.
■ Support for the Fast-Forwarding configuration of edge ports provided
by the 'Fast Start' feature. Fast Start allows a port that is connected to
an endstation to begin forwarding traffic after only 4 seconds. During
this 4 seconds RSTP (or STP) will detect any misconfiguration that may
cause a temporary loop and react accordingly.
■ Easy deployment throughout a legacy network, through backward
compatibility:
■ it will default to sending 802.1D style BPDU's on a port if it receives
packets of this format.
■ it is possible for some ports on a Switch to operate in RSTP
(802.1w) mode, and other ports, for example those connected to a
legacy Switch, to operate in STP (802.1D) mode.
■ you have an option to force your Switch to use the legacy 802.1D
version of Spanning Tree, if required.
What is STP? STP (802.1D) is a bridge-based system that allows you to implement
parallel paths for network traffic and uses a loop-detection process to:
■ Find and disable the less efficient paths (that is, the paths that have a
lower bandwidth).
■ Enable one of the less efficient paths if the most efficient path fails.
RSTP provides the same functionality as STP. For details on how the two
systems differ, see “
How RSTP Differs to STP” on page 40.
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