Frame slip monitoring detects frame deletion and repetition errors in clock synchronization.
See Figure 5: DTA messages on page 49.
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.
Tracking mode There are two thresholds set in LD 73. When a threshold is reached, a DTA
message is, as follows:
DTA015: Maintenance limit for frame slips in tracking mode.
DTA016: Out-of-service limit for frame slips in tracking mode.
Figure 5: DTA messages
Free run (non-tracking) mode
A maintenance threshold and an out-of-service threshold are
set in LD 73. When these thresholds are reached, DTA messages are output. An option in LD
73 can enable automatic recovery after the out-of-service limit has been reached. Related DTA
messages are described below. See
Figure 6: DTA thresholds on page 50.
DTA017: Maintenance limit for frame slips in free run (non-tracking) mode.
The default is 10 slips in 15 seconds.
DTA018: Out-of-service limit for frame slips in free run (non-tracking) mode
without automatic recovery selected. The default is 10 slips in three
seconds.
DTA026: Non-tracking frame slip out-of-service threshold reached while
monitoring frame slip rate for improvement. Trunks remain out of
service. Reset improvement timer.
DTA028: Slip rate improvement criterion is met. Trunks are brought back into
service. Reset improvement timer. (Duration of timer selected in LD
73.)
PRI error detection
ISDN Primary Rate Interface Maintenance November 2011 49
To Next Page
Loading...
Need help?
General
