The "control plane" is the means by which provider edge (PE) routers communicate for auto-discovery and signalling.
An advantage to using PWs as the underlying technology for the data plane is that in the event of failure, traffic will automatically be routed along available backup paths in the service provider's network.
Customers benefit because they can connect all of their sites to an Ethernet VPN that provides a secure, high speed and homogenous network.
Moreover, VPLS provides a logical next step in the continuing evolution of Ethernet from a 10 Mbit/s shared LAN protocol to a multi-Gbps global service.
PEs participating in a VPLS-based VPN must appear as an Ethernet bridge to connected customer edge (CE) devices.
Ethernet does not have a time to live (TTL) field in its frame header, so loop avoidance must be arranged by other means.
The use of a full mesh combined with split horizon forwarding guarantees a loop-free broadcast domain.
For BGP, the control plane scaling issue has long been addressed, through the use of route reflectors (RRs).
To scale the data plane for multicast and broadcast traffic, there is work in progress to use point-to-multipoint LSPs as the underlying transport.
For LDP, a method of subdividing a VPLS VPN into two or three tiered hierarchical networks was developed.
Called hierarchical VPLS (HVPLS), it introduces a new type of MPLS device: the multi-tenant unit (MTU) switch.
This switch aggregates multiple customers into a single PE, which in turn needs only one control and data plane connection into the mesh.
This can significantly reduce the number of LDP sessions and LSPs, and thus unburden the core network, by concentrating customers in edge devices.
Techniques such as redundant pseudowires can provide resiliency in case of failures at the interconnection points.
PE devices may also be equipped with content-addressable memory (CAM), similar to high-end Ethernet switches.
In a VPLS-based VPN with a large number of sites, manually configuring every participating PE does not scale well.