Hello Arun,
A pseudowire is a point-to-point bearer service capable of carrying Layer2 frames across a network between two defined endpoints. A pseudowire can be likened to a direct point-to-point connection between two endpoints - these endpoints consider themselves to be directly interconnected, even though in reality, there is a service provider that interconnects them.
There are various technologies that can be used to provide pseudowire services. One of them is the Any Transport over MPLS, or more recently, the Pseudo Wire Emulation End to End (PWE3), that uses MPLS labeling to create a label switched path over the provider that will carry the frames between two defined endpoints. AToM an PWE3 depend on MPLS being present and run in the service provider's network. Another technology used to provide pseudowire service is the L2TP protocol which is basically a protocol that encapsulates (tunnels) Layer2 frames into new IP packets that are routed over the service provider's network to the endpoints where they are decapsulated and the tunneled Layer2 frames are forwarded further. L2TP is a pure IP-based solution.
Frankly, I do not know what a routed pseudowire is. I haven't heard that term before.
All pseudowire technologies described so far emulate only a point-to-point direct connection. If more than two locations have to be interconnected, more pseudowires are needed. In general, if a full direct connectivity between N locations is necessary, you need to create N*(N-1)/2 pseudowires which is clearly not a scalable approach. Often, however, customers have many locations and request a kind of "Ethernet-alike" connection between them that behaves simply like an Ethernet switch that interconnects all these locations together, allowing immediate direct connectivity between these locations. The pseudowire as a point-to-point service clearly does not fit in here.
This is where Virtual Private LAN Service comes in. The VPLS allows you to interconnect multiple customer locations using an MPLS-based service provider network that emulates an Ethernet switch interconnecting all customer's locations. Apart from allowing all locations to communicate directly to each other, VPLS also takes care of replicating unknown unicast, multicast and broadcast traffic coming from a particular location to all other customer's locations, like a normal Ethernet switch would. VPLS network itself is based on routers running IP and MPLS and all operations are performed over MPLS label switched paths.
Best regards,
Peter
