Avaya CS 1000 - System Synchronization Analysis

All the degradations shown in Table 74: Performance impact of one slip on page 153 can be
controlled or avoided by proper clock (network) synchronization.
Table 74: Performance impact of one slip
Service Potential impact
Encrypted Text Encryption key must be resent.
Video Freeze frame for several seconds. Loud pop on
audio.
Digital Data Deletion or repetition of Data. Possible Misframe.
Facsimile Deletion of 4-8 scan lines. Drop Call.
Voice Band Data Transmission Errors for 0.01 to 2 s. Drop Call.
Voice Possible Click
Clock synchronization can be either tracking, on the primary or secondary reference clock, or
non-tracking (free-run). In LD 73 (prompts PREF and SREF), the 2.0 Mb PRI which supports
the clock controller is defined as the primary clock reference.
Another 2.0 Mb PRI (or DTI) may
be defined as the secondary clock reference. The clock controller synchronizes from the
incoming bit stream of the primary or secondary references. The clock controller in turn
supplies a synchronized reference for the rest of the system, including all 2.0 Mb PRIs and
DTIs.
The 2.0 Mb PRI card detects and reports frame slips (repetitions and deletions) to the system.
The count of slips is recorded (LCNT), printed out, and cleared at each midnight routine.
Frame slips have two alarm thresholds as defined in LD 73. They are as follows:
• Slip — out-of-service threshold. When this threshold (variable count versus variable time)
is reached, the PRI card is placed in an out-of-service state. The card automatically
returns to a normal state if the slip rate improves after the Group I OOS guard timer
expires.
• Slip — maintenance threshold. When this threshold is reached, the PRI card is placed in
a maintenance state that has no impact on call processing. The maintenance state is
simply an indication that a degraded condition exists. The card automatically returns to a
normal state if the slip rate improves after the Group I MAINT guard timer expires.
Define slip thresholds
To define the slip thresholds, use the following commands in LD 73. Times range from 1M to
24H (one 1 minute to 24 hours). Counts are 1 to 255.
Monitor system PRI operation
ISDN Primary Rate Interface Maintenance November 2011 153