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Re: [Roll] [6lo] RPL artifact compression discussion

Michael Richardson <mcr+ietf@sandelman.ca> Tue, 24 March 2015 14:26 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: robert.cragie@gridmerge.com
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Date: Tue, 24 Mar 2015 10:26:38 -0400
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Cc: "roll@ietf.org WG" <roll@ietf.org>, "6lo@ietf.org" <6lo@ietf.org>
Subject: Re: [Roll] [6lo] RPL artifact compression discussion
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Robert Cragie <robert.cragie@gridmerge.com> wrote:
    > 0000 63 04 00 01 00 02 c.....
    > IPv6 extension header
    > 1110 .... = Pattern: IPv6 extension header (0x0e)
    > .... 111. = Header ID: IPv6 header (0x07)
    > .... ...0 = Next header: Inline

What I see here is that when EID=7, that the thing following
is a compressed IPHC.  Is it even possible to have a non-compressed IPv6
header?  Maybe one can do NH=1, and then have an explicit NH=41 byte?

    > This allows IP-in-IP using IPHC compression.

So, in the NHC+ case, we could just define a way to compress RH3, which would
consume the remaining EID value (along with using EID=5 for RPI).  That would
result in a chain of four seperately compressed artifacts.
In my view, the ideal NHC++ proposal (not yet described), might compress all
of the artifacts in a single pass, potentially saving many more bytes.

-- 
Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-

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