"The purpose of this document is to define a BGP-based auto-discovery mechanism for Layer-1 VPNs (L1VPNs). The auto-discovery mechanism for L1VPNs allows the provider network devices to dynamically discover the set of Provider Edges (PEs) having ports attached to Customer Edge (CE) members of the same VPN. That information is necessary for completing the signaling phase of L1VPN connections. One main objective of a L1VPN auto-discovery mechanism is to support the ""single-end provisioning"" model@ where addition of a new port to a given L1VPN would involve configuration changes only on the PE that has this port and on the CE that is connected to the PE via this port."