A PW port represents an extraction point of a payload carried within a tunnel. This payload is extracted onto a PW SAP within a service context (such as a Epipe, VPRN or IES). Various types of tunnels can be supported and the details of each tunnel type whose payload is terminated on a PW port is described in the following sections.
The entry point of a tunnel depends on the routing conditions in the network. To make a distinction between a PW port with a fixed connection to a physical port (a virtual port in the VSR), and a PW port that is free to switch between the ports, the latter is referred to as a Flex PW port.
A Flex PW port is bound to a list of ports, and the tunnel associated with the Flex PW port can be routed (and rerouted) through any port in that list. If traffic is re-routed through a different port because of the failure in the network, the Flex PW port continues to be the terminating point of the tunnel, with minimal packet loss incurred during the switchover. See Figure: Flex PW port.
