A single-homed BGP VPWS service is implemented as an Epipe connecting a SAP or static GRE tunnel (a spoke-SDP using a GRE SDP configured with static MPLS labels) and a BGP signaled pseudowire, maintaining the Epipe properties such as no MAC learning. The MPLS pseudowire data plane uses a two-label stack; the inner label is derived from the BGP signaling and identifies the Epipe service while the outer label is the tunnel label of an LSP transporting the traffic between the two end systems.
Figure 1 shows how this service would be used to provide a virtual leased line service (VLL) across an MPLS network between sites A and B.
An Epipe is configured on PE1 and PE2 with BGP VPWS enabled. PE1 and PE2 are connected to site A and B, respectively, each using a SAP. The interconnection between the two PEs is achieved through a pseudowire that is signaled using BGP VPWS updates over a specific tunnel LSP.