Alcatel-Lucent 7750 SR OS, Руководство по настройке интерфейса

Страница: 51 / 444

Interface Configuration
7750 SR OS Interface Configuration Guide Page 51
APS Far-End Protection Line Failure
An APS far-end protection line (APS-FEPL) failure corresponds to the receipt of a K1 byte in 3
consecutive frames that indicates a signal fail (SF) at the far end of the protection line. This forces
the received signal to be selected from the working line.
If the failure detected persists for 2.5 seconds, a far-end protection line failure alarm is raised.
When the failure is absent for 10 seconds, the alarm is cleared. This alarm can only be raised by
the active port operating in a bi-directional mode.
1+1 Switch Operation Example
Table 15 outlines the steps that a bi-directional protection switching process will go through
during a typical automatic switch.
Table 15: Actions for the Bi-directional Protection Switching Process
Status
APS Commands Sent in K1 and
K2 Bytes on Protection Line
Action
B -> A A -> B At Site B At Site A
No failure
(Protection line is not in use) No request No request No action No action
Working line
Degraded in direction A->B SD on working
channel 1 No request Failure
detected,
notify A and
switch to
protection
line. No action
Site A receives SD failure
condition Same Reverse
request No action Remote failure detected,
acknowledge and switch
to protection line.
Site B receives Reverse
request Same Same No action No action