Locate Alarm Indication Signal Alarms

Purpose

An alarm indication signal (AIS) is sent downstream to signal an error condition. There are two types of AIS alarms:

• Alarm indication signal path (AIS-P) is sent by an LTE to a downstream PTE when an LOS or LOF is detected on a upstream SONET section.
• Alarm indication signal line (AIS-L) is sent by an STE to a downstream LTE when an LOS or LOF is detected on an incoming SONET section.

1. Example of a Router Receiving Only an AIS-P Alarm
2. Example of a Router Receiving Both an AIS-L and AIS-P Alarm

Example of a Router Receiving Only an AIS-P Alarm

Problem

Figure 15 shows a router receiving only an AIS-P alarm. The X indicates that the LOS or LOF occurs in the section between Router 1 and Repeater 1.

Solution

All diagnostics are from the perspective of Router 2 (the Juniper Networks router).

Figure 15: Example of a Router Receiving Only an AIS-P Alarm

Meaning

In Figure 15, the progression of events occurring after the failure is as follows:

1. Repeater 1 detects an LOS or LOF on an incoming SONET section.
2. Repeater 1 sends an AIS-L downstream to ADM1 (LTE).
3. ADM 1 sends an AIS-P to Router 2 (PTE).
4. The only alarm that Router 2 receives is the AIS-P alarm from ADM 1.

Example of a Router Receiving Both an AIS-L and AIS-P Alarm

Problem

Figure 16shows a router receiving both an IS-L and AIS-P Alarm. The X indicates that the LOS or LOF occurs in the section between ADM 2 and Repeater 2.

Solution

All diagnostics are from the perspective of Router 2 (the Juniper Networks router).

Figure 16: Example of a Router Receiving Both an AIS-L and an AIS-P Alarm

What It Means

In Figure 16, the progression of events occurring after the failure is as follows:

1. Repeater 2 detects an LOS or LOF on the incoming section.
2. Repeater 2 sends an AIS-L and AIS-P downstream to Router 2.
3. Router 2 receives both an AIS-L and an AIS-P from Repeater 2.