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Re: [6tisch] [Roll] [6lo] FW: New Version Notification for draft-thubert-6lo-rpl-nhc-02.txt

Carsten Bormann <cabo@tzi.org> Fri, 14 November 2014 16:05 UTC

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From: Carsten Bormann <cabo@tzi.org>
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Date: Fri, 14 Nov 2014 06:05:23 -1000
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To: robert.cragie@gridmerge.com, Routing Over Low power and Lossy networks <roll@ietf.org>
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Cc: Pascal Thubert <pthubert@cisco.com>, "6tisch@ietf.org" <6tisch@ietf.org>, "6lo@ietf.org" <6lo@ietf.org>
Subject: Re: [6tisch] [Roll] [6lo] FW: New Version Notification for draft-thubert-6lo-rpl-nhc-02.txt
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On 14 Nov 2014, at 05:46, Robert Cragie <robert.cragie@gridmerge.com> wrote:
> 
> Question - any reason the value 010001XY was chosen for the escape code?

Note that the escape space is not taken just for RFC 6553 compression; it can be used for encoding other NHCs as well.

The idea was to reserve some space around that so if we want to extend the escape space for some future NHC, we can do so while keeping it contiguous.

Note also that RFC 6282 already has variable length processing for hop limit and address compression, so the impact of adding a third instance is going to be limited.  (I need to write that up some more in draft-*-lwig-6lo.)

Since just about every data packet in a RPL network will carry an RPI, saving a single byte is worth quite some effort.

Grüße, Carsten

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