In BNG deployments, tunneled traffic is typically terminated on PW ports where the payload is extracted and processed by ESM on PW SAPs. There are two modes of operation for PW ports in SR OS:
When a PW port is bound to a specific physical port. A successful mapping between the tunnel and the PW port requires that the tunnel terminates on the same faceplate port (I/O port) to which the PW port is bound. In this mode of operation, PW ports do not support rerouting of tunnels between the I/O ports. For example, if a tunnel is rerouted to an alternate physical port because of a network failure, the PW port becomes non-operational. The only supported tunnel on a fixed PW port is an MPLS based PW.
When a PW port is independent of the faceplate port (I/O port) on which the tunnel is terminated. The PXC based PW port is anchored or bound on the termination side of a port cross connect PXC (which can be either a PXC sub-port or a PXC LAG) under an internally created forward path extension (FPE) PW. The benefit of this type of PW port is that it provides services where the tunnel is switched between the I/O ports because of a network failure.
For more information about PW ports, see the Pseudowire Ports section in the 7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 2 Services and EVPN Guide: VLL, VPLS, PBB, and EVPN.
The router supports the MPLS entropy label (as specified in RFC 6790, The Use of Entropy Labels in MPLS Forwarding) on fixed PW ports. This allows LSR nodes in a network to load-balance labeled packets in a more granular fashion than allowed by simply hashing on the standard label stack. For more information, see the 7450 ESS, 7750 SR, 7950 XRS, and VSR MPLS Guide, Entropy Label.