yer 2 information (e.g., ATM virtual path identifiers and virtual circuit identifiers, or Ethernet MAC addresses, or Frame Relay DLCIs). This is beneficial for organizations that need legacy protocol support and those that feel they can efficiently and cost-effectively manage their own routing environment. They are, in effect, purchasing bandwidth, not the additional services offered by a Layer 3 MPLS VPN. Customers still have the PVC mesh, provisioning, and routing issues, as before, and there may be limitations on what interfaces a carrier will sup- port. Carriers that are evaluating Layer 2 VPNs are challenged by the interconnec- tivity issues associated with Layer 2 VPNs. Support for any-to-any connectivity over Layer 2 MPLS backbones is not widely deployed by any of the major carriers. In most instances, the customer edge routers require common access types, such as Frame Relay-to-Frame Relay or ATM-to-ATM. Ultimately, however, Layer 2 MPLS VPNs will allow customers to attach any Layer 2 access circuit to the MPLS cloud, allowing for diverse and cost-effective interface options. Multiple Layer 2 VPN service models are being analyzed in the industry and by the Provider Provisioned Virtual Private Networking (PPVPN) working group and the Pseudo-Wire Emulation Edge-to-Edge (PWE3) working group. The PPVPN group is working on the Kompella draft, named after Cureda Kompella. The Kompella draft makes use of BGP to allow provider edge routers to communicate with one another about their customer connections. The PWE3 group is working on a draft named the Martini draft, after Luca Martini. The Martini draft makes of the Label Distribution Protocol (LDP) between provider edge routers. Two of the most important Layer 2 VPN models, VPWS and VPLS, are described in the follow- ing sections. VPWS VPWS VPNs are also known as point-to-point pseudo-wires. A pseudo- wire emulates a point-to-point link and provides a single service perceived by its user as an unshared link or circuit of the chosen service. Using encapsulated pse