Re: [Int-area] I-D Action: draft-ietf-intarea-tunnels-05.txt

Joe Touch <touch@isi.edu> Wed, 17 May 2017 18:57 UTC

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To: "Templin, Fred L" <Fred.L.Templin@boeing.com>
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From: Joe Touch <touch@isi.edu>
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Subject: Re: [Int-area] I-D Action: draft-ietf-intarea-tunnels-05.txt
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Hi, Fred,

Circling back to this item:


On 3/29/2017 2:18 PM, Templin, Fred L wrote:
> One other comment. I agree with figures 12 and 13 but (and I think this is
> a crucial point) I think they need a supporting sentence or two explaining
> why the procedure is "fragment then encapsulate" and not "encapsulate
> then fragment".
Will do.

> This is the difference between tunnel fragmentation
> and ordinary outer fragmentation, where your document is correctly
> advocating tunnel fragmentation.
Yeah, but I was unable to find definitive and RFC citations for those
terms ("inner fragmentation" and "outer fragmentation"). 4459 mentions
fragmentation of 'inner' and 'outer', but those terms go back to 2003
and before, and I'm not sure warrant a citation.

> To the best of my knowledge, this was
> first documented in Section 3.1.7 of RFC2764 and should be cited as such.
> At least, that is what Bob B. suggested to me about 10yrs ago.
The idea of differentiating inner and outer fragmentation goes back to
RFC2003 at least, AFAICT.

That section of RFC2764 mentions that outer fragmentation avoids
fragmentation inside the tunnel, but doesn't recommend it (it just says
"alternative"). Further, it claims that none of the existing tunneling
protocols support this (even though RFC2003 does).

I'm not convinced this is worth tracking down for its origins. Let me
know if you feel otherwise, but we'd need stronger evidence AFAICT.

Joe