Pseudowire redundancy provides the ability to protect a pseudowire with a preprovisioned pseudowire and to switch traffic over to the secondary standby pseudowire in case of a SAP or network failure condition. Pseudowires are redundant by the virtue of the SDP redundancy mechanism. For instance, if the SDP is an RSVP LSP and is protected by a secondary standby path, Fast-Reroute paths, or both, the pseudowire is also protected. However, there are a couple of applications in which SDP redundancy does not protect the end-to-end pseudowire path:
There are two different destination PE nodes for the same VLL service. The main use case is the provision of dual-homing of a CPE or access node to two PE nodes located in different POPs. The other use case is the provision of a pair of active and standby BRAS nodes, or active and standby links to the same BRAS node, to provide service resiliency to broadband service subscribers.
The pseudowire path is switched in the middle of the network and the 7210 SAS pseudowire switching node fails.
Pseudowire and VPLS link redundancy extends link-level resiliency for pseudowires and VPLS to protect critical network paths against physical link or node failures. These innovations enable the virtualization of redundant paths across the metro or core IP network to provide seamless and transparent fail-over for point-to-point and multi-point connections and services. When deployed with multi-chassis LAG, the path for return traffic is maintained through the pseudowire or VPLS switchover, which enables carriers to deliver ‟always on” services across their IP/MPLS networks.