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

Carsten Bormann <cabo@tzi.org> Tue, 12 August 2014 08:40 UTC

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From: Carsten Bormann <cabo@tzi.org>
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Date: Tue, 12 Aug 2014 10:40:19 +0200
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To: Routing Over Low power and Lossy networks <roll@ietf.org>
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Cc: Michael Richardson <mcr+ietf@sandelman.ca>, Ole Troan <otroan@employees.org>, 6man WG <ipv6@ietf.org>
Subject: Re: [Roll] WGLC for draft-thubert-6man-flow-label-for-rpl-03
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On 12 Aug 2014, at 09:15, Ines Robles <mariainesrobles@googlemail.com> wrote:

> This technique saves bytes

Again, the straw man at http://tools.ietf.org/html/draft-bormann-6lo-rpl-mesh-00
saves the same number of bytes.  Actually, for common cases, it enables one additional optimization (saving one more byte) that is not available with the flow label hack.  (On the other hand, due to the way RFC 6282 works, the flow label hack saves one byte where both it and ECN are in use and the common case does not apply.)

The disadvantage of the RPL mesh header is that this approach is not available outside 6lo networks (i.e., networks employing adaptation layers that use RFC 6282).  I’m not aware yet of a use case where that is a problem.

In either encoding (RPL mesh header or flow label), it is probably a good idea anyway to unpack the compressed information back into the RPL IPv6 option when leaving the 6lo networks.

Grüße, Carsten