An Overview of VPLS Network Service
VPLS, also known as Virtual Private LAN Service, is a class of Layer 2 Ethernet VPN that allows for the connection of multiple Ethernet sites over MPLS private or metro networks. With a VPLS network, all customer sites appear to be on the same LAN regardless of their geographical location. Each customer site has its own private VPLS that is completely separated from other customers across the shared carrier network. The primary goal of Virtual Private LAN Service (VPLS) is to overcome the limitations posed by ATM and frame relay for providing a protocol-transparent, any-to-any, full-mesh service across a WAN.
VPLS networks are based on an Ethernet interface which simplifies the LAN/WAN boundary for service providers and customers. Therefore, Virtual Private LAN Service (VPLS) allows for rapid and flexible provisioning because the service bandwidth is not tied to the physical interface. For example, a 100Mb interface can support service level agreements with anywhere from 1Mb to 100Mb of customer traffic, typically in increments of 1Mb. Virtual Private LAN Service (VPLS) supports a wide range of bandwidth ranging from 1Mbps to 1Gbps.
A VPLS network utilizes edge routers that can learn, bridge and replicate on a per VPLS location basis. These VPLS edge routers are connected by a fully mesh MPLS Label Switch Path (LPS) tunnels, enabling any-to-any connectivity. With Virtual Private LAN Service (VPLS), multiple applications can be carried within each LPS tunnel. Similar to MPLS networks, all services in a VPLS network are identified by a unique virtual channel label, which is exchanged between each pair of edge routers. Label switch routers in the path switch traffic based on the label, so the virtual channel is only visible to the final edge router where the service terminates. Most companies currently use routers for their WAN connections and the edge routers in a VPLS network are exposed only to a single MAC address at each customer location. This means that each edge router within a VPLS network can scale to support thousands of VPLS services.
The benefits associated with VPLS networks are many. VPLS network technologies are transparent, protocol independent and offer a multipoint solution with shared bandwidth pool for remote locations that belong to a specific customer VPLS domain. With VPLS, customers maintain complete control over their own switching and routing between branch offices which allows for easier configuration and debugging. Virtual Private LAN Service (VPLS) eliminates Layer 2 protocol conversions between LAN and WAN. Ethernet LAN interfaces result in a lower total cost of ownership. With VPLS, there is no training required on WAN network technologies as the case with ATM and frame relay. VPLS services offer bandwidth provisioning on the fly for each subscriber independently per VPLS. VPLS networks utilize auto discovery to add new sites without requiring reconfiguration at existing sites.
