Alcatel Omni Switch/Router, User Manual

Page: 650 / 1100

XMAP
Page 21-4
Common Transmission State
In the common transmission state, ports detect adjacent switch failures or disconnects by
sending Hello packets and waiting for Hello responses. Ports in this state send out Hello
packets at a configurable interval (the default is 5 minutes) called the
common transmission
time . To avoid synchronization with adjacent switches, the common transmission time is
jittered randomly by plus or minus ten percent.
Ports wait for Hello responses using the discovery transmission time (the default is 30
seconds). If Hello responses are detected within one discovery transmission time, the port
remains in the common transmission state. If Hello responses are not detected within one
discovery transmission time, the port reverts to the discovery state.
Passive Reception State
In the passive reception state, switch ports are in receive-only mode. Hello packets are not
sent out from these ports, and there is no timer on waiting for Hello responses. If the port
receives a Hello packet at any time, it enters the common transmission state and transmits a
Hello packet in reply.
If a port transitions to the passive reception state, any remote switch entries for that port are
deleted.
Common Transmission and Remote Switches
If an
XMAP
switch is connected to multiple
XMAP
switches via a hub, the switch sends and
receives Hello traffic to and from the remote switches through the same port. If one of the
remote switches stops sending Hello packets and other remote switches continue to send
Hello packets, the ports in the common transmission state will remain in the common trans-
mission state.
The inactive switch will eventually be aged out of the switch’s
XMAP
database because each
remote switch entry has a “last seen” field that is updated when Hello packets are received.
The switch checks the “last seen” field at least once every common transmission interval.
Switch ports that are no longer “seen” may still retain an entry for up to three common trans-
mission intervals. The slow aging out prevents the port from sending Hello packets right away
to the inactive switch and creating additional unnecessary traffic.