Pointer Justification Count Reference - Cisco ONS 15327 User Documentation

Chapter 8 Performance Monitoring

Pointer Justification Count Reference

IPPM occurs only on STS paths that have IPPM enabled, and TCAs are raised only for PM parameters
on the selected IPPM paths. The monitored IPPMs are STS CV-P, STS ES-P, STS SES-P, STS UAS-P,
and STS FC-P. For more information about enabling IPPM, see Intermediate-Path Performance
Monitoring Reference, page 8-12.
The ONS 15327 performs IPPM by examining the overhead in the monitored path and by reading all of
the near-end path PMs in the incoming direction of transmission. The IPPM process allows the path
signal to pass bidirectionally through the node completely unaltered.
For detailed information about specific PMs, locate the card name in the following sections and review
the appropriate definition.

8.3 Pointer Justification Count Reference

Pointers are used to compensate for frequency and phase variations. Pointer justification counts indicate
timing errors on SONET networks. When a network is out of synchronization, signal jitter and signal
wander occur on the transported signal. Excessive wander can cause terminating equipment to slip. It
also causes slips at the SDH and PDH boundaries.
Slips cause different effects in service. Voice service has intermittent audible clicks. Compressed voice
technology has short transmission errors or dropped calls. Fax machines lose scanned lines or experience
dropped calls. Digital video transmission has distorted pictures or frozen frames. Encryption service
loses the encryption key, causing data to be retransmitted.
Pointers provide a way to align the phase variations in STS and VT payloads. The STS payload pointer is
located in the H1 and H2 bytes of the line overhead. Clocking differences are measured by the offset in
bytes from the pointer to the first byte of the STS synchronous payload envelope (SPE) called the J1
byte. Clocking differences that exceed the normal range of 0 to 782 can cause data loss.
Figure 8-9 shows pointer justification count parameters on the Performance Monitoring screen. You can
enable PPJC and NPJC performance monitoring parameters for LTE cards. See Table 8-2 on page 8-12
for a list of Cisco ONS 15327 LTE cards.
Cisco ONS 15327 User Documentation, R3.3
8-13
June 2002