A PW port is primarily used to provide PW termination with the following characteristics:
Provide access (SAP) based capabilities to a PW which has traditionally been a network port based concept within SR OS. For example, PW payload can be extracted onto a PW-port-based SAPs with granular queuing capabilities (queuing per SAP). This is in contrast with traditional PW termination on network ports where queuing is instantiated per physical port on egress or per MDA on ingress.
Lookup dot1q and qinq VLAN tags underneath the PW labels and map the traffic to different services.
Terminate subscriber traffic carried within the PW on a BNG. In this case PW-port-based SAPs are instantiated under a group interface with Enhanced Subscriber Management (ESM). In this case, a PW-port-based SAP is treated as any other regular SAP created directly on a physical port with full ESM capabilities.
The PW-port coverage expands beyond the TLDP-signaled pseudowires and encompass termination of all tunnel types (MPLS, GRE, VXLAN, L2oGRE, SRv6, and so on) and signaling methods (TLDP, BGP-EVPN, BGP-VPSW, and so on) that can be configured under an Epipe service.
Mapping between PWs and PW ports is performed on one-to-one basis.
There are two modes in which PW port can operate:
a PW port bound to a specific physical port (I/O port)
A successful mapping between the PW and PW port requires that the PW terminates on the same physical port (I/O port) to which the PW port is bound. In this mode of operation, PW ports do not support re-routing of PWs between the I/O ports. For example, if a PW is rerouted to an alternate physical port because of a network failure, the PW port becomes non-operational.
a PW port independent of the physical port (I/O port) on which the PW is terminated
This capability relies on FPE functionality, therefore, the name FPE based PW port. The benefit of such PW port is that it can provide services in cases where traffic within PW is rerouted between I/O ports because of a network failure.
When the PW port is created, the mapping between the PW port and PW depends on the mode of operation and application.
PW port creation:
configure
pw-port <id>
encap-type {dot1q|qinq}
Similar to any other Ethernet-based port, the PW port supports two encapsulation types, dot1q and qinq. Ether-type on a PW port is not configurable and it is set to a fixed value of 0x8100 for dot1q and qinq encapsulation.