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Cisco ONS 15310-MA SDH Reference Manual, Release 9.1 and Release 9.2
78-19417-01
Chapter 11 Performance Monitoring
Intermediate-Path Performance Monitoring
11.2 Intermediate-Path Performance Monitoring
Intermediate-path performance monitoring (IPPM) allows transparent monitoring of a constituent
channel of an incoming transmission signal by a node that does not terminate that channel. You can
program IPPM from the Provisioning > Optical > SDH VC high-order path tab in card view. Many large
ONS 15310-MA SDH networks only use line terminating equipment (LTE), not path terminating
equipment (PTE).
ONS 15310-MA SDH allows monitoring of near-end PM parameter data on individual VC high-order
path payloads by enabling IPPM. After enabling IPPM provisioning on the line card, service providers
can monitor large amounts of synchronous transport signal (VC high-order path) traffic through
intermediate nodes, thus making troubleshooting and maintenance activities more efficient.
IPPM occurs only on VC high-order path paths that have IPPM enabled, and TCAs are raised only for
PM parameters on the selected IPPM paths. The monitored IPPM parameters are VC high-order path
CV-P, VC ES-P, VC SES-P, VC UAS-P.
Note Far-end IPPM is not supported. However, SDH path PM parameters can be monitored by logging into
the far-end node directly.
The ONS 15310-MA SDH perform IPPM by examining the overhead in the monitored path and by
reading all of the near-end path PM parameters 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 PM parameters, locate the card name in the following sections
and review the appropriate definition.
11.3 Pointer Justification Count Performance Monitoring
Pointers are used to compensate for frequency and phase variations. Pointer justification counts indicate
timing errors on SDH networks. When a network is out of sync, jitter and wander occurs on the
transported signal. Excessive wander can cause terminating equipment to slip. It also causes slips at the
synchronous digital hierarchy (SDH) and plesiochronous digital hierarchy (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 transmitted again.
Pointers provide a way to align the phase variations in VC high-order path and VC low-order path
payloads. The VC high-order path 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 VC
high-order path synchronous payload envelope (SPE), called the J1 byte. Clocking differences that
exceed the normal range of 0 to 782 can cause data loss.
You can enable positive pointer justification count (PPJC) and negative pointer justification count
(NPJC) PM parameters for LTE cards. PPJC is a count of path-detected (PPJC-Pdet) or path-generated
(PPJC-Pgen) positive pointer justifications. NPJC is a count of path-detected (NPJC-Pdet) or
path-generated (NPJC-Pgen) negative pointer justifications, depending on the specific PM parameter.
A consistent pointer justification count indicates clock synchronization problems between nodes. A
difference between the counts means that the node transmitting the original pointer justification has
timing variations with the node detecting and transmitting this count. Positive pointer adjustments occur
when the frame rate of the SPE is too slow in relation to the rate of the VC3.