Re: [pmtud] Draft-ietf-pmtud-method-05
Gorry Fairhurst <gorry@erg.abdn.ac.uk> Thu, 10 November 2005 16:15 UTC
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Date: Thu, 10 Nov 2005 08:14:02 -0800
Subject: Re: [pmtud] Draft-ietf-pmtud-method-05
From: Gorry Fairhurst <gorry@erg.abdn.ac.uk>
To: John Heffner <jheffner@psc.edu>
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Cc: Matt Mathis <mathis@psc.edu>, pmtud@ietf.org
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On 8/11/05 10:19 am, "John Heffner" <jheffner@psc.edu> wrote: >> --- >> At the end of section 8.7, the document concludes the minimum safe packet >> size for IPv4 is 68 bytes - why not 576 bytes - some explanation seems to be >> needed. > > From RFC 791: > > Every internet module must be able to forward a datagram of 68 > octets without further fragmentation. This is because an internet > header may be up to 60 octets, and the minimum fragment is 8 octets. > > Every internet destination must be able to receive a datagram of 576 > octets either in one piece or in fragments to be reassembled. > > I'll add a citation. > OK >> --- >> Section 10.1, para 2 >> - I disagree that limiting the largest probe size offers any guarentee that >> TCP FR will not be triggeered. FR *can* still be triggered by packet >> re-ordering (which is why we have a DupACK threshold) - so this doesn't >> eliminate this, but it does mitigate the probability that FR is triggeered. > > I guess what we should say is that if your probe is a full cur_mss > larger than the dupack threshold * cur_mss, a successful probe *will* > trigger fast retransmit (unless you have DSACK), so you don't want to do > that. :) > Yep :-) > I'm tempted to pull the description of this method from the draft since > it's not clear to me it has any benefits over the other way. > > >> --- >> In section 10.2, the I-D seems to advocate using any unassigned Type as >> padding, whilst this is true, it seems to be bad IETF practice to advocate >> this, can we simply request an type to do this instead, it seems clean and >> guards against use of the option for two different purposes. > > We're working on trying to get a PAD chunk type defined. > OK. > >> Security Considerations: >> - I think this section should highlight again the PMTUD DoS vulnerabilbity >> when used in multicast (and refer back to the earlier section. > > Do you mean joining a multicast group doing PMTUD, and reporting a small > MTU? > Yes - although that's not very profound, I think it is very worth stating with a section ref to the text. > Thanks, > -John > _______________________________________________ pmtud mailing list pmtud@ietf.org https://www1.ietf.org/mailman/listinfo/pmtud
- [pmtud] Draft-ietf-pmtud-method-05 Gorry Fairhurst
- Re: [pmtud] Draft-ietf-pmtud-method-05 John Heffner
- Re: [pmtud] Draft-ietf-pmtud-method-05 Gorry Fairhurst