Specifications

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Cisco MGX 8230 Edge Concentrator Installation and Configuration

Release 1.1.31, Part Number 78-11215-03 Rev. B0, May 2001

Chapter2 Module and Service Descriptions

Service Resource Module

A service resource module (SRM) provides three main functions for the service modules:

• Bit Error Rate Testing

• 1:N Service Module Redundancy

• Bulk Distribution Mode

See Figure 2-9 for an illustration of the MGX-SRM-3T3/C front card and the MGX-BNC-3T3-M back

card.

Bit Error Rate Testing

After a service module line or port is put into loopback mode, the SRM can generate a test pattern over

the looped line or port, read the received looped data, and report on the error rate. This operation can be

performed on a complete T1 or E1 line, on a fractional T1 or E1 line, on a SD0 bundle (N x DS0), or on

a single DS0 channel. The SRM can support BERT only one line or channel at a time. BERT is capable

of generating a variety of test patterns, including all ones, all zeros, alternate one zero, double alternate

one zero, 223-1, 220-1, 215-1, 211-1, 29-1, 1 in 8, 1 in 24, DDS1, DDS2, DDS3, DDS4, and DDS5.

1:N Service Module Redundancy

Service module redundancy provides 1:N redundancy for multiple groups of service modules (a

group consists of N active and one standby service module). The redundant service module in a

group must be a superset (with respect to functionality) of the cards. Upon the detection of a failure

in any of the service modules, the packets destined for the failed service module are carried over the

CellBus to the SRM in its chassis. The SRM receives the packets and switches them to the backup

service module via the CellBus.

Bulk Distribution Mode

Each of the T3 ports can be used to support up to 28 multiplexed T1 lines, which are distributed to T1

service module ports in the switch. Called bulk distribution, this feature is performed when the SRM is

in “bulk mode.” The purpose of this feature is to allow large numbers of T1 lines to be supported over

T3 lines rather than over individual T1 lines.

Any T1 channel in a T3 line can be distributed to any eight port service module in any slot . Each

MGX 8230 shelf can support up to 64 T1 lines.

The SRM-3T3 can also be operated in “nonbulk mode” on a port-by-port basis. For a port configured in

nonbulk mode, bulk distribution is disabled and the SRM provides BERT and 1:N redundancy functions

only.

Linking the MGX-SRM-3T3/C to a destination card causes the switch to take CPE traffic through the

MGX-SRM-3T3/C rather than the T1 card’s line module. Linkage is a card-level condition. If you link

just one T1 channel on a service module to the MGX-SRM-3T3/C, the back card on the service module

becomes inoperative, so you must link all other T1 ports on that service module to the MGX-SRM-3T3/C

if you want them to operate.