Table 22: Actions For The Bi-Directional Protection Switching Process - Alcatel-Lucent 7750 Configuration Manual

Port Features
Revertive Switching
The APS implementation also provides the revertive and non-revertive modes with non-revertive
switching as the default option. In revertive switching, the activity is switched back to the working
port after the working line has recovered from a failure (or the manual switch is cleared). In non-
revertive switching, a switch to the protection line is maintained even after the working line has
recovered from a failure (or if the manual switch is cleared).
A revert-time is defined for revertive switching so frequent automatic switches as a result of
intermittent failures are prevented. A change in this value takes effect upon the next initiation of
the wait to restore (WTR) timer. It does not modify the length of a WTR timer that has already
been started. The WTR timer of a non-revertive switch can be assumed to be infinite.
In case of failure on both working and the protection line, the line that has less severe errors on the
line will be active at any point in time. If there is signal degrade on both ports, the active port that
failed last will stay active. When there is signal failure on both ports, the working port will always
be active. The reason is that the signal failure on the protection line is of a higher priority than on
the working line.
Bidirectional 1+1 Switchover Operation Example
Table 22
during a typical automatic switchover.

Table 22: Actions for the Bi-directional Protection Switching Process

Status
No failure
(Protection line is not in use)
Working line
Degraded in direction A->B
Site A receives SD failure
condition
Site B receives Reverse
request
Page 84
outlines the steps that a bi-directional protection switching process will go through
APS Commands Sent in K1 and
K2 Bytes on Protection Line
B -> A
No request
SD on working
channel 1
Same
Same
A -> B At Site B
No request No action
No request Failure
detected,
notify A and
switch to
protection
line.
Reverse No action
request
Same No action
7750 SR Interface Configuration Guide
Action
At Site A
No action
No action
Remote failure detected,
acknowledge and switch
to protection line.
No action