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

[Brian E Carpenter <[e-mail]>]

On 25/07/2018 11:46, Tom Herbert wrote:
> On Tue, Jul 24, 2018 at 3:54 PM, Templin (US), Fred L
> <[e-mail]> 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.

Those words are in RFC2119 already:

>> 4. SHOULD NOT   This phrase, or the phrase "NOT RECOMMENDED" mean that
>>    there may exist valid reasons in particular circumstances when the
>>    particular behavior is acceptable or even useful, but the full
>>    implications should be understood and the case carefully weighed
>>    before implementing any behavior described with this label.
   Brian

> Tom
> 
>> Thanks - Fred
>>
>>> -----Original Message-----
>>> From: Int-area [mailto:[e-mail]] On Behalf Of Wassim Haddad
>>> Sent: Tuesday, July 24, 2018 12:43 PM
>>> To: [e-mail] <[e-mail]>
>>> Cc: [e-mail]
>>> 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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