Re: [TERNLI] Forwarding corrupt packets
Michael Welzl <michael.welzl@uibk.ac.at> Mon, 04 September 2006 16:57 UTC
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Subject: Re: [TERNLI] Forwarding corrupt packets
From: Michael Welzl <michael.welzl@uibk.ac.at>
To: Joe Touch <touch@ISI.EDU>
In-Reply-To: <44FC4DF4.8090004@isi.edu>
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Joe, I couldn't agree more with everything you say here. Cheers, Michael On Mon, 2006-09-04 at 18:01, Joe Touch wrote: > Michael Welzl wrote: > >> The question is the impact of the bad packet. > ... > >> If the transport reacts to corrupt packets - as would be the case with > >> UDP-lite and some configs of DCCP - that would be very bad. The > >> difference is whether we're talking about corrupted data and corrupted > >> headers; corrupt data isn't too bad (that's what UDP-lite and DCCP are > >> designed for). Corrupt headers are VERY bad to forward. > > > > I still don't get it - no matter how you use them, the > > reaction of DCCP and UDP-Lite would always be to silently > > discard a packet if the transport header is wrong, so > > no harm is being done (except for the potential waste of > > bandwidth you mention above, but we agree that this isn't > > substantial). > > Bad body, good header: the harm is the bandwidth to the correct > endpoint; the benefit is that this endpoint knows something legitimate, > and the packet serves as its own corruption signal > > Bad header: the harm is the signal is sent to the WRONG endpoint. > > I reviewed the Feb 2005 discussion on this issue from End2end-interest. > > Here's the summary: > > - IPv6 does NOT, in RFC2640, require link checksums (as UDP-Lite does). > > The relevant text is: > > ------------------------------- > > Although IPv6 (at > > least as I recall) omits the IP checksum because of sufficient link > > checksums to detect corrupted packets, there's no requirement that link > > layers have such checksums (as hinted in the UDP-Lite RFC) - at least > > not in 2460 (anyone else know anywhere else a body is buried in this > > regard?) > ------------------------------- > > I saw no followup to that question. > > - I said that UDP-Lite's requirement of link checksums was an ugly layer > violation. I still think that's the case. > > As far as I can tell, UDP-Lite is relaxing a requirement in IPv6 - > allowing partial link checksums rather than full, but I can't locate > that requirement, as per above. > > --- > > I don't have a problem with forwarding the information to the wrong > place; I have a problem with the wrong place acting on it. You're > assuming that the UDP-Lite partial checksum is sufficient to avoid that; > for some reason, the UDP-Lite authors and WG clearly did not. > > It'd be useful to review the UDP-lite discussions as to why that text > was required so prominently. > > Joe -- Michael Welzl <michael.welzl@uibk.ac.at> University of Innsbruck
- [TERNLI] Forwarding corrupt packets Michael Welzl
- Re: [TERNLI] Forwarding corrupt packets Joe Touch
- Re: [TERNLI] Forwarding corrupt packets Michael Welzl
- Re: [TERNLI] Forwarding corrupt packets Joe Touch
- Re: [TERNLI] Forwarding corrupt packets alessandro salvatori
- Re: [TERNLI] Forwarding corrupt packets Michael Welzl
- Re: [TERNLI] Forwarding corrupt packets Joe Touch
- Re: [TERNLI] Forwarding corrupt packets Michael Welzl
- Re: [TERNLI] Forwarding corrupt packets Gorry Fairhurst
- Re: [TERNLI] Forwarding corrupt packets Michael Tuexen
- Re: [TERNLI] Forwarding corrupt packets Michael Welzl
- Re: [TERNLI] Forwarding corrupt packets Gorry Fairhurst
- Re: [TERNLI] Forwarding corrupt packets Gorry Fairhurst
- Re: [TERNLI] Forwarding corrupt packets Michael Tuexen
- Re: [TERNLI] Forwarding corrupt packets Gorry Fairhurst
- Re: [TERNLI] Forwarding corrupt packets Michael Tuexen
- Re: [TERNLI] Forwarding corrupt packets Joe Touch
- Re: [TERNLI] Forwarding corrupt packets Michael Welzl
- Re: [TERNLI] Forwarding corrupt packets Michael Welzl
- Re: [TERNLI] Forwarding corrupt packets Gorry Fairhurst
- Re: [TERNLI] Forwarding corrupt packets Michael Tuexen
- Re: [TERNLI] Forwarding corrupt packets Gorry Fairhurst
- Re: [TERNLI] Forwarding corrupt packets Michael Tuexen
- Re: [TERNLI] Forwarding corrupt packets Joe Touch
- Re: [TERNLI] Forwarding corrupt packets Michael Tuexen
- Re: [TERNLI] Forwarding corrupt packets Joe Touch
- Re: [TERNLI] Forwarding corrupt packets Michael Tuexen
- Re: [TERNLI] Forwarding corrupt packets Michael Welzl
- Re: [TERNLI] Forwarding corrupt packets Randall Stewart
- Re: [TERNLI] Forwarding corrupt packets Randall Stewart
- Re: [TERNLI] Forwarding corrupt packets Gorry Fairhurst
- Re: [TERNLI] Forwarding corrupt packets Gorry Fairhurst