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 18:25 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>
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From: Fernando Gont <fgont@si6networks.com>
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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.

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