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Re: [Roll] [6lo] Call for advice on the RFC 6553 6lo encoding

Carsten Bormann <cabo@tzi.org> Wed, 15 October 2014 07:59 UTC

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From: Carsten Bormann <cabo@tzi.org>
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Date: Wed, 15 Oct 2014 09:59:26 +0200
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To: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
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Cc: Routing Over Low power and Lossy networks <roll@ietf.org>, "6tisch@ietf.org" <6tisch@ietf.org>, "6lo@ietf.org" <6lo@ietf.org>
Subject: Re: [Roll] [6lo] Call for advice on the RFC 6553 6lo encoding
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On 15 Oct 2014, at 09:52, Pascal Thubert (pthubert) <pthubert@cisco.com> wrote:

> b) Conservative. RPL would only consume a very limited NHC space, at the expense of one extra octet in each packet.

No, that’s not how it [1] works.

There is no extra byte except if the R or F flags in the RPL Packet Information (RPI) are non-zero.

It appears to me that those flags are an infrequent occurrence, so the total expense in bytes sent should be near zero.  There *is* expense in code size (complexity), though.

I have not been able to obtain any real world numbers on the frequency of non-zero R bits in real life RPL traffic.
(I have no idea whether non-zero F bits actually exist in real life at all.)
Those would be questions that people with more RPL experience than I have can answer.

Grüße, Carsten

[1] http://tools.ietf.org/html/draft-bormann-6lo-rpl-mesh-02

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