Multi-Chassis Automatic Protection Switching Overview

Automatic protection switching (APS) is a linear protection scheme designed to protect VLAN-based Ethernet networks.

With APS, a protected domain is configured with two paths: a working path and a protection path. Both working and protection paths can be monitored. Normally, traffic is carried on the working path (that is, the working path is the active path), and the protection path is disabled. If the working path fails, its protection status is marked as degraded (DG) and APS switches the traffic to the protection path, then the protection path becomes the active path.

APS uses two modes of operation: linear 1+1 protection switching architecture and linear 1:1 protection switching architecture. The linear 1+1 protection switching architecture operates with either unidirectional or bidirectional switching. The linear 1:1 protection switching architecture operates with bidirectional switching.