Re: [Int-area] Alissa Cooper's No Objection on draft-ietf-intarea-frag-fragile-16: (with COMMENT)

Fernando Gont <fgont@si6networks.com> Thu, 05 September 2019 00:34 UTC

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From: Fernando Gont <fgont@si6networks.com>
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Subject: Re: [Int-area] Alissa Cooper's No Objection on draft-ietf-intarea-frag-fragile-16: (with COMMENT)
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On 4/9/19 16:46, Templin (US), Fred L wrote:
> Hi Fernando,
> 
>> -----Original Message-----
>> From: Fernando Gont [mailto:fgont@si6networks.com]
>> Sent: Tuesday, September 03, 2019 2:45 PM
>> To: Templin (US), Fred L <Fred.L.Templin@boeing.com>om>; Tom Herbert <tom@herbertland.com>om>; Bob Hinden
>> <bob.hinden@gmail.com>
>> Cc: int-area@ietf.org; IESG <iesg@ietf.org>rg>; Joel Halpern <joel.halpern@ericsson.com>om>; draft-ietf-intarea-frag-fragile@ietf.org;
>> intarea-chairs@ietf.org
>> Subject: Re: [Int-area] Alissa Cooper's No Objection on draft-ietf-intarea-frag-fragile-16: (with COMMENT)
>>
>> On 4/9/19 00:02, Templin (US), Fred L wrote:
>>> Fernando,
>>>
>>>> -----Original Message-----
>>>> From: Fernando Gont [mailto:fgont@si6networks.com]
>>>> Sent: Tuesday, September 03, 2019 1:49 PM
>>>> To: Tom Herbert <tom@herbertland.com>om>; Bob Hinden <bob.hinden@gmail.com>
>>>> Cc: Templin (US), Fred L <Fred.L.Templin@boeing.com>om>; int-area@ietf.org; IESG <iesg@ietf.org>rg>; Joel Halpern
>>>> <joel.halpern@ericsson.com>om>; draft-ietf-intarea-frag-fragile@ietf.org; intarea-chairs@ietf.org
>>>> Subject: Re: [Int-area] Alissa Cooper's No Objection on draft-ietf-intarea-frag-fragile-16: (with COMMENT)
>>>>
>>>> On 3/9/19 23:33, Tom Herbert wrote:
>>>>> Bob,
>>>>>
>>>>> I agree with Fred. Note, the very first line of the introduction:
>>>>>
>>>>> "Operational experience [Kent] [Huston] [RFC7872] reveals that IP
>>>>> fragmentation introduces fragility to Internet communication".
>>>>>
>>>>> This attempts to frame fragmentation as being generally fragile with
>>>>> supporting references. However, there was much discussion on the list
>>>>> about operational experience that demonstrates fragmentation is not
>>>>> fragile.
>>>>
>>>> Discussion is not measurements. Do you have measurements that suggest
>>>> otherwise?
>>>>
>>>> We did separate measurements, with different methodologies, and they
>>>> suggest the same thing. You can discuss as much as you want. But that
>>>> will not make fragmentation work.
>>>>
>>>>
>>>>
>>>>> In particular, we know that fragmentation with tunnels is
>>>>> productively deployed and has been for quite some time. So that is the
>>>>> counter argument to the general statement that fragmentation is
>>>>> fragile. With the text about tunneling included in the introduction I
>>>>> believe that was sufficient balance of the arguments, but without the
>>>>> text the reader could be led to believe that fragmentation is fragile
>>>>> for everyone all the time which is simply not true and would be
>>>>> misleading.
>>>>
>>>> "fragile" means that it fails in an uncceptably large number of cases.
>>>> ~30 failure rate is not acceptable. ~20% isn't, either.
>>>
>>> What if we fragment the payload packet instead of the delivery packet?
>>> Wouldn't that give a 0% failure rate?
>>
>> Sure. At which point you are using ip fragmentation in a limited domain,
>> and that's *not* the case this document is addressing, right?
> 
> As I just answered to Ole, it is not only for limited domains but also for over
> the open Internet. The fragmentation footprint is the same as the tunnel
> footprint.

Sorry, maybe I'm missing something: If you fragment the outeer packet,
you better don't because fragmentation is fragile. If you fragment the
inner packet, the the outer packet is not fragmented, so from the pov of
the Internet you're not generating fragmented traffic.

Am I missing something?

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
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