Nortel Networks R2MFC Manuel D’Utilisation

64 Chapter 6 R2MFC MBM maintenance

NN40010-300

Performance is monitored on both the internal (PRI) and external (MFC) links, but the actions 
when errors occur are different. Alarms and events handling include three types of actions:

1 Propagating Alarms:

a Alerts the far-end by transmitting remote alarm indication (RAI).

b Passes alarm conditions from link to link.

2 Reflecting alarm conditions on faceplate LEDs

3 Printing to error logs

This section describes the mechanism and terminology of alarms measurements, and the actions 
taken when alarms occur or stop. Several performance indicators are monitored in order to detect 
E1 signal degradation; these indicators are categorized into two groups:

•

Group I errors: These are events that can be counted, and are not continuous conditions. The 
number of events is counted, and is compared with thresholds (number of events in a specific 
time interval) used to evaluate the severity of the alarm condition.

•

Group II errors: These are continuous conditions. These indicators can turn on and off 
rapidly, or they can remain on or off.

Each group of performance indicators are handled differently.

Each error has two thresholds of error rate, which defines two levels of error severity:

•

Maintenance — error exists but acceptable (service available)

•

Out Of Service (OOS) — severe error (service not available)

Group I errors are the following:

1 Bipolar Violations (BPV) — Errors in the bits coding.

2 Frame Bit Error (FBER) — Errors in the frame alignment word.

3 SLIPs — The replication or deletion of the 256 payload bits of an E1 frame. This error 

indicates that the local E1 clock is not synchronized with the far end.

4 CRC-4 errors — Received CRC code is not identical to a locally calculated code. This alarm 

is only relevant when in CRC-4.

5 Far-end block error (FEBE) — Far end has detected a CRC-4 error. This alarm is only 

relevant when in CRC-4.