MPLS VPN
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MPLS VPN is a family of methods for harnessing the power of Multiprotocol Label Switching (MPLS) to create Virtual Private Networks (VPNs). MPLS is well suited to the task as it provides traffic isolation and differentiation without substantial overhead.
A layer 3 MPLS VPN, also known as L3VPN, combines enhanced BGP signaling, MPLS traffic isolation and router support for VRFs (Virtual Routing/Forwarding) to create a virtual network.
This solution is more scalable and less costly than classic provider-based frame relay or ATM-based networks, or IPsec-based VPNs. Layer 3 MPLS VPNs also support Quality of Service.
A layer 2 MPLS VPN, also known as L2VPN, is a point-to-point pseudowire service. It can be used to replace existing physical links. The specification is based on the Martini drafts, which define methods to transport layer 2 packets across MPLS networks, and methods to encapsulate transport protocols such as ATM, Ethernet, and SONET.
The primary advantage of this MPLS VPN type is that it can transparently replace an existing dedicated facility without reconfiguration, and that it is completely agnostic to upper-layer protocols. By contrast, in a layer 3 VPN the hosts must speak IP.
A multipoint layer 2 VPN for Ethernet, can be implemented using Virtual Private LAN Service (VPLS) and MPLS pseudo wires (ATOM).
It builds on the foundation of point-to-point layer 2 MPLS VPNs to extend an ethernet broadcast domain across multiple sites. The VPLS network appears as a private ethernet switch to the attached MPLS end site.