Re: [Roll] WGLC for draft-thubert-6man-flow-label-for-rpl-03

Brian E Carpenter <brian.e.carpenter@gmail.com> Wed, 30 July 2014 01:36 UTC

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Date: Wed, 30 Jul 2014 13:36:44 +1200
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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To: Philip Levis <pal@cs.stanford.edu>
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Cc: Brian Haberman <brian@innovationslab.net>, "ipv6@ietf.org" <ipv6@ietf.org>, Michael Richardson <mcr+ietf@sandelman.ca>, roll <roll@ietf.org>, Ines Robles <mariainesrobles@googlemail.com>, Bob Hinden <bob.hinden@gmail.com>, Ole Troan <otroan@cisco.com>
Subject: Re: [Roll] WGLC for draft-thubert-6man-flow-label-for-rpl-03
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On 30/07/2014 12:02, Philip Levis wrote:
...
> "This specification suggests that energy-saving is another
> compelling reason for a violation to the aforementioned
> rule."
> 
> makes the assumption that the energy saving is significant.
> Breaking the end-to-end nature of the flow label for some
> tiny saving seems like a mistake. 

I can't evaluate whether the energy saving is significant.
However, I don't have any deep faith in the e2e-ness of the
flow label. The reality (as RFC 6437 tries to recognise)
is that it's a mutable field, and is therefore untrustworthy
for e2e use. It has value for load balancing if all packets
of a given flow have the same label, whether the label is
set by the source or by a border device. For that reason,
I think the usage proposed in this draft is OK.

However, I do agree that at least a hand-waving estimate of
the % energy saving would be useful.

    Brian Carpenter