Subject: RE: [Sigtran] Re:n+k issue

From: "Ong, Lyndon" <[email-masked]>
Date: Thu, 26 Jun 2003 18:16:18 -0700

Hi Folks,

At the risk of blowing up the issue (although I think we
are there already), I would like to make the following
points:

-- the issue of n+k is in fact confusing in the RFC text
  - n+k as defined in the introduction is subject to multiple
    interpretations
  - n+k has the following procedure defined in 4.3.4.3 -
  "For the n+k redundancy case, ASPs which are in that AS should
   coordinate among themselves the number of active ASPs in the AS, and
   should start sending traffic only after n ASPs are active."
    This seems to imply that traffic should only be resumed after
    n ASPs are active, even if traffic is sent from the SG the ASPs
    should not reply.
  - the examples in 5.1.4 and 5.2.3 also appear to reflect this usage.
  - n+k is not clearly reflected in the current state diagrams

Given that this appears to be a valid issue with the RFC and
there seems to be a greater weight of opinion on the side of
the proposed text I believe that the rough consensus exists
supporting the proposed text in the M3UA implementor's guide draft.

However, I understand the concern on the part of some folks
that have interpreted n+k differently.  As a result I think
we also should add clarifying text to the n+k definition in
1.4.4.1 stating that in this definition, traffic is not sent
until "n" ASPs are active, and that the "k" ASPs may be either 
active at the same time as "n" or kept inactive until needed
due to a failed or unavailable ASP.  Hopefully that will 
cover other situations acceptably.

Cheers,

L. Ong

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