Avaya C360 Manager, Installation And Configuration Manual

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Avaya C360 Layer 2 Features
132 Installation and Configuration Guide Avaya C360 Multilayer Stackable Switches, version 4.5
Spanning Tree per Port
The Spanning Tree can take up to 30 seconds to open traffic on a port. This delay can cause
problems on ports carrying time-sensitive traffic. You can therefore enable/disable Spanning
Tree in C360 on a per-port basis to minimize this effect.
Rapid Spanning Tree Protocol (RSTP)
About the 802.1w Standard
The enhanced feature set of the 802.1w standard includes:
●
Bridge Protocol Data Unit (BPDU) type 2
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New port roles: Alternate port, Backup port
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Direct handshaking between adjacent bridges regarding a desired topology change (TC).
This eliminates the need to wait for the timer to expire.
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Improvement in the time it takes to propagate TC information. Specifically, TC information
does not have to be propagated all the way back to the Root Bridge (and back) to be
changed.
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Origination of BPDUs on a port-by-port basis.
Port Roles
At the center of RSTP-specifically as an improvement over STP (802.1d)-are the roles that are
assigned to the ports. There are four port roles:
●
Root port - port closest to the root bridge
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Designated port - corresponding port on the remote bridge of the local root port
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Alternate port - an alternate route to the root
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Backup port - an alternate route to the network segment
The RSTP algorithm makes it possible to change port roles rapidly through its fast topology
change propagation mechanism. For example, a port in the "blocking" state can be assigned
the role of "alternate port." When the backbone of the network fails the port may be rapidly
changed to forwarding.
Whereas the STA passively waited for the network to converge before turning a port into the
forwarding state, RSTP
actively confirms that a port can safely transition to forwarding without
relying on any specific, programmed timer configuration.