[6tisch] Proposed improvement in RH3-6LoRH

"Pascal Thubert (pthubert)" <pthubert@cisco.com> Mon, 18 January 2016 17:54 UTC

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From: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
To: "6lo@ietf.org" <6lo@ietf.org>
Thread-Topic: Proposed improvement in RH3-6LoRH
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Date: Mon, 18 Jan 2016 17:54:05 +0000
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Cc: "6tisch@ietf.org" <6tisch@ietf.org>, Routing Over Low power and Lossy networks <roll@ietf.org>
Subject: [6tisch] Proposed improvement in RH3-6LoRH
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Dear all

The picture below illustrates how the RH3 6LoRH works with draft 03 in a case like Root -> A -> B -> C -> leaf

[cid:image003.png@01D15221.72C5D060]

The first 6LoRH is expected to be a full address (128 bits) to set up a reference and the next 6LoRH are expected to be smaller and just override the rightmost bits which form the delta from the reference.

Proposal: we could consider that the 128bits source of the IP header before the RH3 is the reference to start with.

With that even the first hop could be compressed the same way as the other hops. With RPL, the root is the encapsulator if IP in IP in used. Good thing, in that case the root is totally elided with the IP-in-IP 6LoRH.

So this simple proposal saves up to 16 octets (that's in the case with a single subnet and all addresses differ only by the last 2 bytes). I'm willing to add it in the next revision.

Any opposition?

Pascal