Service providers (SPs) are seeking to replace their synchronous optical networking (SONET) gear. Traditionally, the current widely adopted solution for offering access ring dual-homing for Ethernet line (E-Line) services involves configuring a service using virtual private LAN service (VPLS) on provider edge (PE) nodes. This ensures that both PE nodes terminating the access ring are meshed with remote PE node(s) and ready for forwarding upon any failure. This solution, however, has several shortcomings. First, this approach has scalability implications, as a bridge-domain may be required on the PE node for every point-to-point (p2p) service. A majority of platforms are not capable of scaling bridge-domains as high as the number of p2p services required in many cases. Second, media access control (MAC) address learning may be required even though the service is p2p, hence wasting platform resources. Third, flooded traffic (unknown unicast, broadcast, and multicast) may be delivered from the core to both PE nodes, only to have one of the two copies be dropped at the port that is blocking on the ring.
Another solution is to use a virtual private wire service (VPWS) on the PE nodes complemented with multiple VLAN registration protocol (MVRP) (IEEE 802.1ak) running on all the access ring switches, as well as the PE nodes. The disadvantage of this mechanism is that MVRP (and MRP in general) use a ‘stop and forward’ paradigm, where the MVRP messages need to be stopped and processed by the switch control plane on a hop-by-hop basis upon failure. Therefore, with this solution it is unlikely to be possible to meet the key 50 msec failover time requirement.