Re: [Int-area] Discussion about Section 6.1 in draft-ietf-intarea-frag-fragile

"Templin (US), Fred L" <Fred.L.Templin@boeing.com> Fri, 13 September 2019 14:07 UTC

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From: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>
To: Ole Troan <otroan@employees.org>
CC: Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org>, "int-area@ietf.org" <int-area@ietf.org>
Thread-Topic: [Int-area] Discussion about Section 6.1 in draft-ietf-intarea-frag-fragile
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Date: Fri, 13 Sep 2019 14:07:49 +0000
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Subject: Re: [Int-area] Discussion about Section 6.1 in draft-ietf-intarea-frag-fragile
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Ole,

> -----Original Message-----
> From: Ole Troan [mailto:otroan@employees.org]
> Sent: Friday, September 13, 2019 5:00 AM
> To: Templin (US), Fred L <Fred.L.Templin@boeing.com>
> Cc: Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org>rg>; int-area@ietf.org
> Subject: Re: [Int-area] Discussion about Section 6.1 in draft-ietf-intarea-frag-fragile
> 
> Fred,
> 
> > Ron, it is just a drop in the bucket compared with the amount of discussion since
> > "Fragmentation Considered Harmful (1987)". But, I think we now clearly see a
> > case where  fragmentation is *required*.
> 
> Absolutely. As tunnels produce a new link-layer, that can (should) be a function of that link-layer.
> Network layer fragmentation is not needed for that.
> (For the purpose of making the point and to set future direction, ignoring existing IP tunnel mechanisms).

New tunnel protocols like GUE can specify their own link adaptation schemes in
an encapsulation sublayer above the outer IP layer. Section 5 of "GUE Extensions"
specifies exactly such a scheme:

https://datatracker.ietf.org/doc/draft-ietf-intarea-gue-extensions/

However, existing tunnel protocols like RFC2473 and RFC4213 do not have the
option of inserting an encapsulation sublayer and have no alternative but to
employ IP fragmentation.

Fred

> Cheers,
> Ole