[PWE3] [Technical Errata Reported] RFC4385 (1743)

[RFC Errata System <rfc-editor at rfc-editor.org>]

The following errata report has been submitted for RFC4385,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN".

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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=4385&eid=1743

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Type: Technical
Reported by: Yaakov (J) Stein <yaakov_s at rad.com>

Section: 4, 4.1, 4.2

Original Text
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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.

Corrected Text
--------------
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 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
-----
While the fact that the TDM PWs always require the sequence number and thus 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 is causing confusion to implementers.

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RFC4385 (draft-ietf-pwe3-cw-06)
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Title               : Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN
Publication Date    : February 2006
Author(s)           : S. Bryant, G. Swallow, L. Martini, D. McPherson
Category            : PROPOSED STANDARD
Source              : Pseudo Wire Emulation Edge to Edge
Area                : Internet
Stream              : IETF
Verifying Party     : IESG