Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile

"Templin (US), Fred L" <Fred.L.Templin@boeing.com> Wed, 25 July 2018 14:34 UTC

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From: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>
To: Tom Herbert <tom@herbertland.com>
CC: Wassim Haddad <wassim.haddad@ericsson.com>, "internet-area@ietf.org" <int-area@ietf.org>, "intarea-chairs@ietf.org" <intarea-chairs@ietf.org>
Thread-Topic: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
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Date: Wed, 25 Jul 2018 14:34:26 +0000
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Subject: Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
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Hi Tom,

You are right that I have been experimenting with iperf3 in a closed network, but
it would work just fine (and exhibit the same behavior) on the open Internet.

The thing about iperf3 is that it sends random data that is simply recorded for
performance metric purposes and then dropped. So, iperf3 doesn't care if it
is causing IP reassembly-related packet loss or even corruption.

So, there is a class of applications that knowingly engage IP fragmentation
without fear of what might go wrong during the subsequent reassembly. 
This class of applications might bear mention in the draft.

Thanks - Fred

> -----Original Message-----
> From: Tom Herbert [mailto:tom@herbertland.com]
> Sent: Tuesday, July 24, 2018 4:46 PM
> To: Templin (US), Fred L <Fred.L.Templin@boeing.com>
> Cc: Wassim Haddad <wassim.haddad@ericsson.com>om>; internet-area@ietf.org <int-area@ietf.org>rg>; intarea-chairs@ietf.org
> Subject: Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
> 
> On Tue, Jul 24, 2018 at 3:54 PM, Templin (US), Fred L
> <Fred.L.Templin@boeing.com> wrote:
> > I have an observation that I would like to see addressed in the document. Some applications
> > (e.g., 'iperf3' and others) actually leverage IP fragmentation to achieve higher data rates than
> > are possible using smaller (but unfragmented) whole packets.
> >
> > Try it - by default, iperf3 sets an 8KB UDP packet size and allows packets to fragment across
> > paths that support only smaller MTUs. I have seen iperf3 exercise IP reassembly at line rates
> > on high-speed links, i.e., it shows that reassembly at high rates is feasible.
> >
> > We know from RFC4963 that there are dangers for reassembly at high rates, but there are
> > applications such as iperf3 that ignore the "SHOULD NOT" and leverage IP fragmentation
> > anyway. So, should the "SHOULD NOT" have an asterisk?
> >
> Fred,
> 
> My reading of the draft is that IP fragmentation is fragile on the
> open Internet and should be avoided for applications that run over the
> Internet. That doesn't mean that fragmentation should be avoided in
> all use cases. In particular, if fragmentation is used in a closed
> network with low loss and has appropriate security measures in place,
> then it can be beneficial. I suspect that describes the network that
> your're running iperf in. If this interpretation of the draft's intent
> is correct, maybe there could be some words to clarify that.
> 
> Tom
> 
> > Thanks - Fred
> >
> >> -----Original Message-----
> >> From: Int-area [mailto:int-area-bounces@ietf.org] On Behalf Of Wassim Haddad
> >> Sent: Tuesday, July 24, 2018 12:43 PM
> >> To: internet-area@ietf.org <int-area@ietf.org>
> >> Cc: intarea-chairs@ietf.org
> >> Subject: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
> >>
> >> Dear all,
> >>
> >> We would like to start a WG adoption call for draft-bonica-intarea-frag-fragile (“IP Fragmentation Considered Fragile”).
> >>
> >> https://www.ietf.org/id/draft-bonica-intarea-frag-fragile-03.txt
> >>
> >>
> >> Please indicate your preferences on the mailling list. The deadline is August 10th.
> >>
> >>
> >> Thanks,
> >>
> >> Juan & Wassim
> >> _______________________________________________
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