Cisco Systems MGX 8230 manual Automatic Protection Switching on the PXM1, APS Requirements

Chapter 6 Card and Service Configuration

The Processor Switching Module

UNI cell headers typically apply where a workstation connects through a line to a PXM1 UNI port (rather than a SLIP-based port on the PXM1-UI card). Such an implementation is not common, so cnfatmln usually is not necessary.

Automatic Protection Switching on the PXM1

Automatic Protection Switching (APS) provides redundancy for an OC-3 or OC-12 line on the PXM1 (if a failure occurs someplace other than the PXM1 front card). The failure can originate on the daughter card, uplink card, or any part of the physical line.

With APS, the active PXM1 remains active and passes the cells from the failed line-path through the redundant line. The advantage of APS is that a line switchover requires significantly less time than a full PXM1 switchover.

Note A failure of the PXM1 front card in a redundant system causes the entire PXM1 card set to switch over.

As defined in GR-253, a variety of APS modalities are possible (see the command summaries that follow).

APS Requirements

The current requirements for APS service on an MGX 8230 shelf are:

•Redundant PXM1s (currently, the PXM1 does not support an APS configuration where the working and protection lines on the same uplink card).

•A “B” version of an OC-3 or OC-12 back card (SMLR-1-622/B, and so on).

•The connected network shelf or CPE must also support APS.

APS Configuration

Initial APS specification consists of the working and protection slot and line and the mode for APS. After the initial APS specification, you can configure additional APS parameters, give commands for switching lines, and display the APS configuration. The CiscoView application and CLI provide access to the APS feature. For detailed descriptions of the CLI commands, see the Cisco MGX 8230 Wide Area Edge Switch Command Reference. Note that APS is available for only the “B” versions of the SONET cards—SMLR-1-622/B, and so on. The applicable CLI commands are:

•addapsln to specify the lines and mode for APS

•cnfapsln to modify the following details of APS operation:

–error thresholds

–wait period before the PXM1 restores the working line after errors clear

–unidirectional or bidirectional switchover, which specifies whether one or both directions of a line are switched when the criteria for a hard or soft failure are met for one direction

–revertive recovery, where the working line automatically returns to operation after errors clear and any wait period has elapsed

	Cisco MGX 8230 Edge Concentrator Installation and Configuration
Release 1.1.31, Part Number 78-11215-03 Rev. B0, May 2001		6-9