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Status: Verified (1)

RFC4385, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", February 2006

Source of RFC: pwe3 (int)

Errata ID: 1743

Status: Verified
Type: Technical

Reported By: Yaakov (J) Stein
Date Reported: 2009-03-26
Verifier Name: Adrian Farrel
Date Verified: 2011-08-03

Section 4, 4.1, 4.2 says:

The sequence number mechanism described here uses a circular unsigned
16-bit number space that excludes the value zero.
...
o The sequence number that follows 65535 (maximum unsigned 16-bit
  number) is one.
...
o If the sequence number on the packet is zero, the sequence
  integrity of the packets cannot be determined.  In this case, the
  received packet is considered to be in order.

It should say:

The sequence number mechanism for all PW types except the TDM PWs 
SAToP [RFC4335], CESoPSN [RFC5086], and TDMoIP [RFC5087] use a 
circular unsigned 16-bit number space that excludes the value zero. 
The sequence numbers for TDM PWs include the value zero.
...
o For all non-TDM PWs the sequence number that follows 65535 
(maximum unsigned 16-bit number) is one.
...
o If the sequence number on a non-TDM-PW packet is zero, the sequence
  integrity of the packets cannot be determined.  In this case, the
  received packet is considered to be in order.

Notes:

The fact that the TDM PWs always require sequence number and do not give a zero value special meaning was well-known and documented in the relevant RFCs. However, this was forgotten in this document and has caused confusion to implementers.


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