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 14:37 UTC

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To: Tom Herbert <tom@herbertland.com>
Cc: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>, Ole Troan <otroan@employees.org>, Bob Hinden <bob.hinden@gmail.com>, Joel Halpern <joel.halpern@ericsson.com>, "draft-ietf-intarea-frag-fragile@ietf.org" <draft-ietf-intarea-frag-fragile@ietf.org>, "int-area@ietf.org" <int-area@ietf.org>
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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 5/9/19 17:31, Tom Herbert wrote:
> On Wed, Sep 4, 2019 at 5:34 PM Fernando Gont <fgont@si6networks.com> wrote:
>>
>> On 4/9/19 18:26, Templin (US), Fred L wrote:
>>> Hi Ole,
>>>
>>>> -----Original Message-----
>>>> From: Ole Troan [mailto:otroan@employees.org]
>>>> Sent: Wednesday, September 04, 2019 7:37 AM
>>>> To: Templin (US), Fred L <Fred.L.Templin@boeing.com>
>>>> Cc: Bob Hinden <bob.hinden@gmail.com>om>; Tom Herbert <tom@herbertland.com>om>; Joel Halpern <joel.halpern@ericsson.com>om>; draft-
>>>> ietf-intarea-frag-fragile@ietf.org; int-area@ietf.org
>>>> Subject: Re: [Int-area] Alissa Cooper's No Objection on draft-ietf-intarea-frag-fragile-16: (with COMMENT)
>>>>
>>>> Fred,
>>>>
>>>> I removed the IESG from this list, as we seem to have drifted into a more general fragmentation discussion as opposed to discussing
>>>> the exact changes to this draft.
>>>>
>>>>>>>> Why is that more useful than what is in 3.5? If it’s not making a recommendation, why call this out in the introduction.  There are
>>>> lot
>>>>>> of
>>>>>>>> other things it doesn’t make recommendations about that aren’t in the Introduction either.
>>>>>>>
>>>>>>> Because it sets a more appropriate tone and lets the reader know from the onset that
>>>>>>> fragmentation and encapsulation go hand in hand. And tunnel fragmentation avoids the
>>>>>>> issues raised by others in this thread.
>>>>>>
>>>>>> While inner fragmentation ensures the fragment will reach the tunnel tail end, a tunnel endpoint will typically not reassemble that
>>>>>> fragment, so will generate fragments after the tunnel hop.
>>>>>> Inner fragmentation is only available on IPv4.
>>>>>
>>>>> Not true. For IPv6 packets, simply insert a GUE header or an RFC2473 header and
>>>>> fragment on that. The fragments will be reassembled by the tunnel tail end, then
>>>>> passed to the next hop as a whole IPv6 packet. The fragmentation footprint is
>>>>> therefore the same as the tunnel footprint.
>>>>
>>>> Is that not the exact definition of outer fragmentation?
>>>
>>> No. I am talking about outer header (OH) followed by tunnel header (TH) followed
>>> by inner packet (IP). Recipe:
>>>
>>>   1) wrap the IP in a TH to create a tunnel packet (TP)
>>>   2) fragment the TP
>>>   3) encapsulate each tunnel fragment in an independent OH
>>>   4) send each outer packet (OP). These will look like ordinary
>>>        unfragmented IP packets, but will contain a tunnel fragment
>>
>> This looks like a recent claim from the IAB that QUIC has shown that it
>> is possible to deploy new transport protocols on the Internet. -- when
>> quick employs UDP, and hence from the pov of the Internet, UDP is the
>> transport protocol.
>>
>> Same with your example: you are tunneling your fragments. The Internet
>> will not see fragments. *That* is why it would work.
>>
>> i.e., if you want fragmentation to not be fragile on the Internet, the
>> trick is that packets shouldn't look like fragmens ;-)
>>
> Fernando,
> 
> Sure, if we dress up protocols in UDP there is a greater probability
> they can traverse the Internet. But this doesn't always work and it's
> fallacious to think that unbiquitously solves the problem of protocol
> ossification.

I fully agree with that. In fact, encapsulating transport protocols in
UDP *circumvents* the problem -- it doesn't actually fix it.



>  I really wish the IAB would look at the issues of wide
> spread middlebox non-conformance-- this is the root problem and a
> fundamental deterrent to evolving the Internet IMO.

FWIW, I did ask about this in the context of EH-insertion on the IAB's
architecture list.

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