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Re: Use cases for PMTUD and PLPMTUD (was: RE: 6MAN: Adoption call on draft-hinden-6man-rfc1981bis-01)

Fernando Gont <fgont@si6networks.com> Fri, 05 February 2016 20:18 UTC

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Subject: Re: Use cases for PMTUD and PLPMTUD (was: RE: 6MAN: Adoption call on draft-hinden-6man-rfc1981bis-01)
To: "Templin, Fred L" <Fred.L.Templin@boeing.com>, "otroan@employees.org" <otroan@employees.org>
References: <2134F8430051B64F815C691A62D983183395EFC6@XCH-BLV-105.nw.nos.boeing.com> <56B4E91C.6090905@si6networks.com> <2134F8430051B64F815C691A62D983183395F14A@XCH-BLV-105.nw.nos.boeing.com>
From: Fernando Gont <fgont@si6networks.com>
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Date: Fri, 05 Feb 2016 17:15:55 -0300
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Cc: Bob Hinden <bob.hinden@gmail.com>, 6man WG <ipv6@ietf.org>, "Fred Baker (fred)" <fred@cisco.com>
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On 02/05/2016 04:00 PM, Templin, Fred L wrote:
> Hi Fernando,
> 
>> -----Original Message-----
>> From: Fernando Gont [mailto:fgont@si6networks.com]
>> Sent: Friday, February 05, 2016 10:26 AM
>> To: Templin, Fred L; otroan@employees.org
>> Cc: Bob Hinden; 6man WG; Fred Baker (fred)
>> Subject: Re: Use cases for PMTUD and PLPMTUD (was: RE: 6MAN: Adoption call on draft-hinden-6man-rfc1981bis-01)
>>
>> On 02/05/2016 03:13 PM, Templin, Fred L wrote:
>>> Starting this under a new thread, IMHO if we want to promote RFC1981 to standard
>>> we should understand its use cases as well as the use cases for RFC4821.
>>>
>>> First, it is reasonable to expect that paths that begin and end within the same
>>> well-managed administrative domain can be counted on to deliver the necessary
>>> ICMPs. An example is my employer's corporate network. In that case, traditional
>>> PMTUD per RFC1981(bis) can be applied alone w/o having to apply RFC4821.
>>>
>>> On the other hand, paths that lead to Internet destinations cannot be counted
>>> on to deliver the necessary ICMPs. In that case, RFC4821 provides a mitigation.
>>>
>>> But, if we do not believe that there are paths for which traditional PMTUD
>>> can still be used safely, then we should be working to deprecate RFC1981
>>> instead of making it a standard.
>>
>> Well, the thing here that you can do RFC1981-only, RFC4821-only, or
>> RFC1981/RFC4821 (should I say "dual stack"? :-) ).
>>
>> With that in mind, one could as well have both RFC1981 and RFC4821 as
>> standards, I guess...
>>
>> But yes, generally speaking, RFC1981-only is certaianly unreliable.
> 
> Except for within well-managed administrative domains where RFC1981-only
> is sufficient. They do exist; I am typing this message from within one right now.

I'd expect 6man to produce protocols that work everywhere, rather than
just on some subset scearios...

-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492

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