Re: [tcpm] comments on draft-ietf-tcpm-icmp-attacks-05

Joe Touch <touch@ISI.EDU> Sun, 14 June 2009 14:57 UTC

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Date: Sun, 14 Jun 2009 07:56:51 -0700
From: Joe Touch <touch@ISI.EDU>
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To: Florian Weimer <fw@deneb.enyo.de>
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Cc: "tcpm@ietf.org" <tcpm@ietf.org>, Fernando Gont <fernando@gont.com.ar>, Fernando Gont <fernando.gont@gmail.com>
Subject: Re: [tcpm] comments on draft-ietf-tcpm-icmp-attacks-05
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Florian Weimer wrote:
> * Fernando Gont:
> 
>>> For instance, I'm not certain that setting the DF bit is only
>>> possible for hosts that support PMTUD ... is there a reference for
>>> that?
>> What's the reason for setting the DF flag for IP packets carrying TCP
>> segments if you don't implement PMTUD?
> 
> You don't have to put randomness into the IP ID field (at least in
> theory; in practice, DF=1 packets get fragmented, too).

Technically, you do regardless of whether the bit is set or not right
now. Hopefully that requirement will change, but only when we change the
standards.

See draft-touch-intarea-ipv4-unique-id-01

Joe
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