Frame Slip - Nortel Communication Server 1000S Maintenance Manual

Page 60 of 210 Primary Rate Interface maintenance
Table 10
BIPV thresholds
Level
least tolerant
1
2
3
4
most tolerant

Frame slip

553-3001-517 Standard 2.00
For example, if the default BIPV thresholds are used, DTA011 is output when
the number of errors exceed 15.4 per second. DTA012 is output when the
number of errors exceeds 154 per second.
When the error rate improves two levels, the PRI is restored to service unless
the 24-hour out-of-service counter was exceeded.
Error rate
>10-3 (1544 BPV per s)
>10-4 (154 BPV per s)
>10-5 (15.4 BPV per s)
>10-6 (1.54 BPV per s)
Digital signals must have accurate clock synchronization for data to be
interleaved into or extracted from the appropriate timeslot during
multiplexing and demultiplexing operations. Frame slip monitoring detects
frame deletion and repetition errors in clock synchronization. See Figure 5 on
page 61.
Clock synchronization can be either tracking, on the primary or secondary
reference clock, or free run (non-tracking). In LD 73 (prompts PREF and
SREF), one PRI may be defined as the primary clock reference. Another may
be defined as the secondary clock reference. All others are defined as free run.
PRI hardware detects frame slips in tracking and free run modes. For tracking
mode, running the midnight routines prints the number of overflows and
clears the counter. For free run mode, running the midnight routines prints the
number of frame deletions and repetitions and clears the counters.
September 2004
Elapsed time Number of BPV allowed
(seconds)
0.6639
6.639
66.39
663.9
during elapsed time
1025
1025
1025
1025