Cisco Systems MGX 8230 manual Circuit Emulation Service Module for T3 and E3, Features

Chapter 6 Card and Service Configuration

Circuit Emulation Service Module for T3 and E3

Circuit Emulation Service Module for T3 and E3

The main function of the Circuit Emulation Service Module (CESM) is to provide a constant bit rate (CBR) service. The CESM converts data streams into CBR AAL1 cells according to the CES-IS specifications of the ATM Forum for unstructured transport across an ATM network. Unstructured transport means the CESM does not interpret or modify framing bits, so a high-speed CESM creates a single data pipe The most common application is legacy support for digitized voice from a PBX or video from a codec. Using circuit emulation, a company can expand its data communication network without specific voice or video cards to meet its voice or teleconferencing requirements.

The higher speed CESM uses a T3 or E3 line. The card set consists of an MGX-CESM-T3 or MGX-CESM-E3 front card and either a BNC-2T3 or BNC-2E3 back card. In this CESM application, only one line on the two-port back card is operational. Furthermore, it supports one logical port and one logical connection (as a data pipe) on the line and runs at the full T3 or E3 rate. Although the typical connection setup is the three-segment connection across an ATM network, the CESM can support a DAX connection. Up to 26 CESM card sets can operate in an MGX 8230 shelf.

Features

The MGX-CESM-T3 or MGX-CESM-E3 provide the following:

•Unstructured data transfer at 44.736 Mbps (1189980 cells per second) for T3 or 34.368 Mbps (91405 cells per second) for E3

•Synchronous timing by either a local clock sourced on the PXM1 or loop timing (transmit clock derived from receive clock on the line)

•1:1 redundancy is through a Y-cable

•Programmable egress buffer size (in the form of cell delay variation)

•Programmable cell delay variation tolerance (CDVT)

•Per VC queuing for the transmit and receive directions

•An idle code suppression option

•Bit count integrity when a lost AAL1 cell condition arises

•Alarm state definitions per G.704

•Trunk conditioning by way of framed AIS for T3 and unframed, alternating 1s and 0s for E3

•On-board bit error rate testing (BERT)

Cell Delay Treatment

You can configure a tolerable variation in the cell arrival time (CDVT) for the receive buffer. After an underrun, the receiver places the contents of the first cell to arrive in a receive buffer then plays it out at least one CDVT value later. The maximum cell delay and CDVT (or jitter) are:

•For T3

–Cell delay of 4 msec

–CDVT of 1.5 msec in increments of 125 microseconds

	Cisco MGX 8230 Edge Concentrator Installation and Configuration
6-38	Release 1.1.31, Part Number 78-11215-03 Rev. B0, May 2001