Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN

Application of Ethernet Pseudowires to MPLS Transport Networks

“…[RFC5085] specifies that the first nibble is set to 0x1 to indicate a channel associated with a pseudowire [RFC4385].…”

Encapsulation Methods for Transport of Asynchronous Transfer Mode (ATM) over MPLS Networks

“…The Control Words defined in this section are based on the Generic PW MPLS Control Word as defined in [RFC4385]. They provide the ability to sequence individual frames on the PW, avoidance of equal-cost multiple-path load-balancing (ECMP) [RFC2992], and OAM mechanisms including VCCV [VCCV].…”

“…[ RFC4385] states, "If a PW is sensitive to packet misordering and is being carried over an MPLS PSN that uses the contents of the MPLS payload to select the ECMP path, it MUST employ a mechanism which prevents packet misordering." This is necessary because ECMP implementations may examine the first nibble after the MPLS label stack to determine whether or not the labelled packet is IP.…”

“…For a given emulated VC and a pair of routers PE1 and PE2, if PE1 supports packet sequencing, then the sequencing procedures defined in [RFC4385] MUST be used.…”

Media Access Control (MAC) Address Withdrawal over Static Pseudowire

“…The lack of a reliable transport protocol for the in-band OAM necessitates a presence of sequencing and acknowledgement scheme so that the receiver can recognize newer message from retransmitted older messages. [RFC4385] describes the details of sequence-number handling, which includes overflow detection for a Sequence Number field size of 16 bits. This document leverages the same scheme with the two exemptions:…”