Re: 6MAN Minutes, Actions, and Document Status

Fernando Gont <fgont@si6networks.com> Thu, 26 April 2012 23:55 UTC

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Date: Thu, 26 Apr 2012 17:53:28 -0300
From: Fernando Gont <fgont@si6networks.com>
Organization: SI6 Networks
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Subject: Re: 6MAN Minutes, Actions, and Document Status
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Cc: "ipv6@ietf.org Mailing List" <ipv6@ietf.org>, Bob Hinden <bob.hinden@gmail.com>
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Hi, Ole,

On 04/26/2012 08:50 AM, Ole Trøan wrote:
>> I think that draft-gont-6man-predictable-fragment-id is also ready 
>> for wg call for adoption as wg document -- I've rev'ed the
>> document since IETF 83 in response to the feedback received during
>> my presentation (i.e., just require the Frag ID to be
>> unpredictable, without mandating any particular algorithm).
> 
> the chairs have an action item on taking this to the mailing list. 
> there was an issue that I believe Bob raised, if we were going to 
> have publish RFCs on every field in TCP/IP protocols that should
> have unpredictable values, or if we should have a generic
> recommendation applying to protocol design in general.

I believe that a generic document about protocol design that discusses
this issue would be valuable, such that *new* protocols and protocol
implementations do not incur into this problem. However, in this
particular case (Fragment ID), the IPv6 standard itself is suggesting
to use a counter, and hence the spec should be fixed.

That aside, different fields have different requirements. For example,
the constraints for randomizing the transport protocol ports are
different from those of producing unpredictable IDs, and different from
those of say, randomizing the TCP sequence numbers, or randomizing the
IPv6 Flow Label. The consequences of the particular approach that you
follow vary quite a bit in each case.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492