Spanning Tree; Understanding Rstp And Mstp - FibroLAN Falcon-RX/812/G/A User Manual

Falcon R-Class | User Guide

4.15 Spanning Tree

Spanning Tree Protocol was developed to protect Ethernet networks from the bad effects of network
loops: a loop is a circular path in the network which causes frame storms that overloads the Ethernet
network.
Spanning Tree Protocol creates a spanning tree within a mesh network of connected Ethernet bridges
and disables the links which are not part of that tree, leaving a single active path between any two
network nodes.
Note: Spanning Tree is available in all Falcon R devices
Spanning Tree Versions:
•
802.1d Legacy Spanning Tree
•
802.1w Rapid Spanning Tree
Faster topology conversion by:
A faster method for temporary loop prevention: STP waits for the new topology to stabilize while
RSTP makes the new root port forwarding immediately once all prior root ports have been made
blocking, and then uses handshaking (on point-to-point links) to make designated ports forwarding
as well.
Improvements in topology change detection, notification, and flushing of the learn tables.
•
802.1s Multiple-Instance Spanning Tree
A newer version supporting more than a single topology: each instance (group of VLANs) can have
its own topology.

Understanding RSTP and MSTP

4.15.1.1 Understanding RSTP
STP provides basic loop prevention functionality with slow network convergence when topology
changes occur.
RSTP converges faster because a handshake mechanism is deployed, based on P2P links instead of
the timer-based process used by STP.
Under RTSP, port assignments change through exchanged messages RSTP device generates
configuration messages once every hello time interval.
An RTSP device will respond to BPDUs sent from the root bridge. The RSTP device will propose its
spanning tree information to its designated ports.
If another RSTP device receives this information and determines that this is the superior root
information, it starts a synchronizing operation to ensure all its ports are in sync with the new
information. This device may send an "agreement" to the first RSTP device confirming its superior
spanning tree information.
183