Configuring Frame Format - HP ProCurve Secure 7000dl Series Basic Management And Configuration Manual

Configuring the E1 + G.703 and T1 + DSX-1 Modules
Configuring the E1 + G.703 Module
9-8
AMI uses alternating positive and negative voltage (referred to as alternating
polarity, or bipolarity) to represent logical ones, and zero voltage to represent
logical zeros. Because AMI uses zero voltage for logical zeros, it can cause
synchronization loss between peers at each end of a WAN connection when
a data stream contains a long string of logical zeros.
Although HDB3 is based on AMI, HDB3 prevents synchronization loss by
limiting the number of consecutive zeros in a data stream to four. HDB3
replaces the zeros with three logical zeros and a violation bit with the same
polarity as the last AMI logical one detected.
HDB3 is the most common line-coding scheme used in E1-carrier lines and is
the default setting for all E1 interfaces on the ProCurve Secure Router.
To configure the line coding, use the following command:
Syntax: coding [ami | hdb3]
For example, to configure the coding option to ami, you would enter:
ProCurve(config-e1 1/2)# coding ami
Because HDB3 is the default setting, you do not have to enter the coding
command if your PBX uses HDB3.

Configuring Frame Format

E1 interfaces on the ProCurve Secure Router support two frame formats:
E1
Cyclic Redundancy Check 4 (CRC4)
In the E1 frame format, a channel (or timeslot) is called a TS, and the 32
channels are numbered TS0 to TS31. Two channels are used to establish and
maintain synchronization and signaling; specifically, TS0 is used for synchro-
nization, error detection, and alarms, and TS16 is used for signaling. The other
channels are used to transmit data or voice.
CRC4 is based on the E1 frame format but includes additional error detection.
A checksum bit is included in all even E1 frames with CRC4 format: frame
numbers 0, 2, 4, 6, 8, 10, 12, and 14. A total of 8 checksum bits are used.