Cisco Cisco IGX 8400 Modules Troubleshooting Guide

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

This error applies to the IGX Broadband Trunk Module (BTM) with a T3 backcard.

There are no specific requirements for this document.

This document is not restricted to specific software and hardware versions.

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

The 

C−bit Parity Errs

 counter indicates that in−service, end−to−end bit errors are received during

transmission. There are three C−bits (control bits) that control bit stuffing in each DS3 subframe. The BTM
only supports the DS3 C−bit parity−frame format, which does not require the 21 C−bits for bit−stuffing
control. The DS3−level C−bits are used for in−service, end−to−end path performance monitoring and in−band
data links. The three C−bits in subframe 3 are called CP (C−bit Parity) bits and are used for DS3 path parity.
At the DS3 transmitter, the CP−bits are set to the same value as the two P−bits and are not recomputed in the
network. Because CP−bits are not changed by transmission equipment, they provide end−to−end path
monitoring when evaluated at the receiver. DS3 C−bit parity frame−format offers significant advantages over
the M13 frame format. M13 only supports P−bit parity for local segment error detection.

The likely location of equipment errors is shown in yellow: