RFC 6870 PW Preferential Forwarding Status Bit

This document describes a mechanism for signaling the active and standby status of redundant Pseudowires (PWs) between their termination points. A set of Redundant PWs is configured between Provider Edge (PE) nodes in single-segment pseudowire (SS-PW) applications or between Terminating Provider Edge (T-PE) nodes in Multi-Segment Pseudowire (MS-PW) applications. In order for the PE/T-PE nodes to indicate the preferred PW to use for forwarding PW packets to one another, a new status bit is defined. This bit indicates a Preferential Forwarding status with a value of active or standby for each PW in a redundant set. In addition, a second status bit is defined to allow peer PE nodes to coordinate a switchover operation of the PW. Finally, this document updates RFC 4447 by adding details to the handling of the PW status code bits in the PW Status TLV.