The FPE based PW-port is primarily used to extract a PW payload onto an access based PW-port SAP, independent of the network I/O ports. FPE uses Port Cross-Connect (PXC) ports and provides an anchoring point for PW-port, independent of I/O ports, the term anchored PW-port can be interchangeably used with the term FPE based PW-port. The following are examples of applications which rely on FPE based PW-port:
ESM over PW where MPLS/GRE based PW can be rerouted between I/O ports on an SR OS node without affecting ESM service
Granular QoS per PW because the PW payload is terminated on an access based PW-port SAP → ingress/egress queues are created per SAP (as opposed to per network port on egress and per MDA on network ingress)
PW-SAP with MPLS resiliency, where the LSP used by the PW terminated on a PW Ports is protected using MPLS mechanisms such as FRR and could therefore use any port on the system
PW-port using LDP-over-RSVP tunnels
A PW Port using a BGP VPWS
Although the primary role of FPE based PW-port is to terminate an external PW, in certain cases PW-port can be used to terminate traffic from regular SAP on I/O ports. This can be used to:
Separate service termination point from the SAPs which are tied to I/O ports.
Distribute load from a single I/O port to multiple line cards based on S-Tag (traffic from each S-tag can be mapped to a separate PW associated with different PXCs residing on different line cards).