user manual

AT-GS950/48PS Switch Web Interface User’s Guide
67
.
Forwarding
Delay and
Topology
Changes
If there is a change in the network topology due to a failure, removal, or
addition of any active components, the active topology also changes. This
may trigger a change in the state of some blocked ports. However, a
change in a port state is not activated immediately.
It may take time for the root bridge to notify all bridges that a topology
change has occurred, especially if it is a large network. A temporary data
loop could occur if a topology change is made before all bridges have
been notified and that could adversely impact network performance.
To forestall the formation of temporary data loops during topology
changes, a port designated to change from blocking to forwarding passes
through two additional states - listening and learning - before it begins to
forward frames. The amount of time a port spends in these states is set by
the forwarding delay value. This value states the amount of time that a port
spends in the listening and learning states prior to changing to the
forwarding state.
Table 2. Valid Port Priority Values
Step
Port
Priority
10
216
332
448
564
680
796
8112
9 128
10 144
11 160
12 176
13 192
14 208
15 224
16 240