VPLS as described in RFC 4905, Encapsulation methods for transport of layer 2 frames over MPLS, is a class of virtual private network service that allows the connection of multiple sites in a single bridged domain over a provider-managed IP/MPLS network. The customer sites in a VPLS instance appear to be on the same LAN, regardless of their location. VPLS uses an Ethernet interface on the customer-facing (access) side, which simplifies the LAN/WAN boundary and allows for rapid and flexible service provisioning.
VPLS offers a balance between point-to-point Frame Relay service and outsourced routed services (VPRN). VPLS enables each customer to maintain control of their own routing strategies. All customer routers in the VPLS service are part of the same subnet (LAN), which simplifies the IP addressing plan, especially when compared to a mesh constructed from many separate point-to-point connections. The VPLS service management is simplified because the service is not aware of nor participates in the IP addressing and routing.
A VPLS service provides connectivity between two or more SAPs on one (which is considered a local service) or more (which is considered a distributed service) service routers. The connection appears to be a bridged domain to the customer sites so protocols, including routing protocols, can traverse the VPLS service.
Other VPLS advantages include:
VPLS is a transparent, protocol-independent service.
There is no Layer 2 protocol conversion between LAN and WAN technologies.
There is no need to design, manage, configure, and maintain separate WAN access equipment, which eliminates the need to train personnel on WAN technologies such as Frame Relay.