APS overview

Overview
CAUTION 

CAUTION

Service Disruption

An NE transmits data only on the working line.

For a single failure, this configuration can cause a delay of up to 100 ms during an APS switch.

On the NFM-P, the main APS elements are the following:

Table 38-1, Events affecting 1+1 protection The following table describes the events that affect 1+1 protection and their relative priority.

Table 38-1: Events affecting 1+1 protection

Priority

Event

Event type

1

Lockout of protection

User initiated

2

Signal failure on protection line

Automatically initiated

3

Forced switch

User initiated

4

Signal failure on working line

Automatically initiated

5

Signal degradation

Automatically initiated

6

Manual switch

User initiated

7

WTR time (revertive switching only)

User initiated (state request)

8

No reversion (non-revertive switching only)

User initiated (state request)

Consider the following when configuring APS:

Bidirectional mode

In 1+1 system bidirectional mode, a signal failure in either direction causes both the near-end and far-end NEs to switch to the protection channels. The highest-priority local request is compared with a remote request; the request that has the greater priority is selected. See Table 38-1, Events affecting 1+1 protection for the list of events that affect 1+1 protection.

Unidirectional mode

In a 1+1 system unidirectional mode, the working interface switches to the protection interface only for the direction in which a signal failure occurs. For example, if there is a signal failure in the transmit direction, the working interface switches to the protection interface for transmission but not for the receipt of data.