Re: [Int-area] IPv6 fragmentation for IPv4

Tom Herbert <tom@herbertland.com> Tue, 23 May 2017 17:38 UTC

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From: Tom Herbert <tom@herbertland.com>
Date: Tue, 23 May 2017 10:38:12 -0700
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To: "Templin, Fred L" <Fred.L.Templin@boeing.com>
Cc: "int-area@ietf.org" <int-area@ietf.org>, Joe Touch <touch@isi.edu>
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Subject: Re: [Int-area] IPv6 fragmentation for IPv4
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On Tue, May 23, 2017 at 9:17 AM, Templin, Fred L
<Fred.L.Templin@boeing.com> wrote:
> Joe, I wanted to run an idea by you. We all know that IPv4 fragmentation has
> problems because of the 16-bit ID field. So, why not insert an IPv6 Fragment
> Header between the IPv4 header and the upper layer protocol data, then
> use IPv6-style fragmentation instead of IPv4 fragmentation?
>
Hi Fred,

What is the use case for this? Unlike IPv6, IPv4 fragmentation can be
done a routers so this technique wouldn't work in that case. If the
fragmentation is occurring at tunnel ingress its probably just as easy
to fragment as part of the encapsulation like we do in GUE.

Tom

> So, the IPv4 Protocol field would be set to '44', the IPv4 header would be
> followed by an IPv6 Fragment Header, and the "Next Header" field in the
> IPv6 Fragment Header would be set to the Protocol Number for the upper
> layer protocol. Then, upon fragmentation, each fragment would have an
> IPv4 header followed by an IPv6 Fragment Header.
>
> This format is shown in Figure 6 in Appendix A of the AERO draft:
>
> https://datatracker.ietf.org/doc/draft-templin-aerolink/
>
> Does this look like something that should be broken out and put into a
> little standalone document?
>
> Thanks - Fred
>
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