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

Tom Herbert <tom@herbertland.com> Tue, 24 July 2018 23:46 UTC

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From: Tom Herbert <tom@herbertland.com>
Date: Tue, 24 Jul 2018 16:46:16 -0700
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To: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>
Cc: Wassim Haddad <wassim.haddad@ericsson.com>, "internet-area@ietf.org" <int-area@ietf.org>, "intarea-chairs@ietf.org" <intarea-chairs@ietf.org>
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Subject: Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
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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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>> Int-area@ietf.org
>> https://www.ietf.org/mailman/listinfo/int-area
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