Re: [Roll] [6tisch] Support of flow label to carry the RPL information in data packets

Fernando Gont <fgont@si6networks.com> Thu, 17 April 2014 22:54 UTC

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Date: Thu, 17 Apr 2014 19:43:44 -0300
From: Fernando Gont <fgont@si6networks.com>
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To: Brian E Carpenter <brian.e.carpenter@gmail.com>, Fernando Gont <fernando@gont.com.ar>
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Cc: "6tisch@ietf.org" <6tisch@ietf.org>, "6man@ietf.org" <6man@ietf.org>, roll <roll@ietf.org>, Ines Robles <mariainesrobles@googlemail.com>
Subject: Re: [Roll] [6tisch] Support of flow label to carry the RPL information in data packets
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Hi, Brian,

On 04/17/2014 05:31 PM, Brian E Carpenter wrote:
>>
>> On 04/17/2014 11:27 AM, Pascal Thubert (pthubert) wrote:
>>> Considering the support we have at 6TiSCH and ROLL for the work, I
>>> published draft-thubert-6man-flow-label-for-rpl-00.txt to the 6MAN WG.
>>>
>>> The main discussion is probably to confirm whether our proposed use of
>>> the flow label inside the RPL domain is compatible with the goals that
>>> are achieved by RFC6437. Let us continue the discussion there from now on.
>>
>> I just skimmed through the I-D. Two quick questions:
>>
>> 1) Does your document propose/require that the Flow Label be rewritten
>> by some border router? -- I ask because, at the time, there was strong
>> opposition to this.
> 
> It was of course contested, but we have to remember that the flow label
> is an unauthenticated field, so our interpretation of it has to be
> robust against altered values. RFC 6437 indeed covers the case where a
> forwarding node sets the flow label.

FWIW, I was just asking to get an overall/quick understanding of where
they wanted to go, and contrast that where 6man seemed to want to go at
the time. Just that. IHMO, if the point/use case is valid, we should
"evaluate" their proposal (i.e., by no means I was meaning "6man doesn't
like that, forget it".)


>> 2) Does the algorithm/scheme with which you'll rewrite the Flow-Label
>> lead to predictable sequences? And/or, would the resulting values have a
>> uniform distribution?
> 
> The same part of RFC 6437 does RECOMMEND a uniform distribution.

Agreed. Again, I was checking the extent to which they might be
deviating from that was set here.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
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