Cisco Cisco IGX 8400 Modules Troubleshooting Guide

Introduction
 Prerequisites
      Requirements
      Components Used
      Conventions
 Error Definition
 Error Example
 Troubleshooting
 Related Information

This document discusses the Broadband Trunk Module (BTM) parity bit (P−bit) error and provides steps to
troubleshoot this error message.

There are no specific requirements for this document.

The information in this applies to the Cisco IGX" BTM with a T3 interface card.

The information in this document was created from the devices in a specific lab environment. All of the
devices used in this document started with a cleared (default) configuration. If your network is live, make sure
that you understand the potential impact of any command.

For more information on document conventions, refer to the Cisco Technical Tips Conventions.

The 

P−bit Parity Errs

 counter indicates that in−service bit errors have been received during

transmission. There are two P−bits that contain parity information in the digital signal level 3 (DS3) frame.
The P−bits are located in the first bit position in block 1 of subframes 3 and 4. The DS3 source computes
parity over all DS3 information bits after the first X−bit in a DS3 frame. The computed parity information is
inserted in the two P−bits of the subsequent frame. The value of both P−bits is always the same. Both P−bits
are set to 1, if the previous DS3 frame contained an odd number of ones; both P−bits are set to 0, if the
previous DS3 frame contained an even number of ones. Because P−bits are recomputed by each facility
section of the DS3 path, they do not provide a way to monitor the path from end−to−end.