Re: [Int-area] IPv6 fragmentation for IPv4

Tom Herbert <tom@herbertland.com> Tue, 23 May 2017 17:59 UTC

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From: Tom Herbert <tom@herbertland.com>
Date: Tue, 23 May 2017 10:59:06 -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 10:44 AM, Templin, Fred L
<Fred.L.Templin@boeing.com> wrote:
> Hi Tom,
>
> I am thinking about source-fragmentation only, then send all fragments with
> DF=1 so they won't be further fragmented in the network.
>
> One use case would be for IP-in-IPv4 tunneling when there is no GUE header.
> I haven't thought much about other use cases, but it should apply to any IP/X
> encapsulations (X could be TCP, for example).
>
Introducing extension headers in IPv4 might be opening a can of worms.
Could this be done in a new IPv4 option?

Tom

> Thanks - Fred
>
>> -----Original Message-----
>> From: Tom Herbert [mailto:tom@herbertland.com]
>> Sent: Tuesday, May 23, 2017 10:38 AM
>> To: Templin, Fred L <Fred.L.Templin@boeing.com>
>> Cc: int-area@ietf.org; Joe Touch <touch@isi.edu>
>> Subject: Re: [Int-area] IPv6 fragmentation for IPv4
>>
>> 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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>> > Int-area@ietf.org
>> > https://www.ietf.org/mailman/listinfo/int-area
>