48 CHAPTER 4: USING RESILIENCE FEATURESThe protocol is a part of the IEEE Std 802.1D, 1998 Edition bridgespecification. To explain STP more effectively, your Switch will be referredto as a bridge.Rapid Spanning TreeProtocol (RSTP)The Rapid Spanning Tree (RSTP) is an enhanced Spanning Tree feature.RSTP implements the Spanning Tree Algorithm and Protocol, as defined inthe IEEE Std 802.1w-2001.Some of the benefits of RSTP are: Faster determination of the Active Spanning Tree topology throughouta bridged network. Support for bridges with more than 256 ports. Support for the Fast-Forwarding configuration of edge ports providedby the 'Fast Start' feature. Fast Start allows a port that is connected toan endstation to begin forwarding traffic after only 4 seconds. Duringthis 4 seconds RSTP (or STP) will detect any misconfiguration that maycause a temporary loop and react accordingly.If you have Fast Start disabled on a port, the Switch will wait for 30seconds before RSTP (or STP) lets the port forward traffic. Easy deployment throughout a legacy network, through backwardcompatibility: it will default to sending 802.1D style BPDU's on a port if it receivespackets 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 alegacy Switch, to operate in STP (802.1D) mode. you have an option to force your Switch to use the legacy 802.1Dversion of Spanning Tree, if required.What is STP? STP (802.1D) is a bridge-based system that allows you to implementparallel paths for network traffic and uses a loop-detection process to: Find and disable the less efficient paths (that is, the paths that have alower bandwidth). Enable one of the less efficient paths if the most efficient path fails.
