Subject: [PWE3] Sequence number simpler test

From: Stewart Bryant <[email-masked]>
Date: Fri, 23 Sep 2005 14:47:18 +0100

As part of the IESG review process it has been requested that we
move the sequence number description for the skip zero case to
the CW draft, and to include an appendix with a pseudo-code
description.

In tidying up the wording of the sequence number description
and getting the text reviewed by a collegue, it was pointed
out that there is a much simpler check.

I think that we need to keep the algorithm that we have used
for so long (which BTW is a SHOULD, not a MUST even for the
skip zero cases).

However I am considering adding the following text at the end
of the non-normative pseudo-code section.

+++++++
The algorithm described above is the algorithm that has been used
through-out the development of PWE3 and by other standards development
organisations. However a simplified test in which the frame is
considered in order if

(unsigned16)((unsigned16)RECEIVED – (unsigned16)EXPECTED))
<= 32768)

produces the same result except in some cases where the difference
between the frame sequence number and the expected sequence number
is 32768, and should be considered an equivalent test.

+++++++

What do others think? Is it useful to include this, or is it
just baggage?

I will submit the revised CW draft to WG LC when I have some
feedback on this point.

Thanks

Stewart

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