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Re: [trill] Fwd: Mail regarding draft-ietf-trill-over-ip

Joe Touch <touch@isi.edu> Tue, 05 May 2015 17:54 UTC

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Date: Tue, 05 May 2015 10:53:32 -0700
From: Joe Touch <touch@isi.edu>
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To: "Templin, Fred L" <Fred.L.Templin@boeing.com>, Xuxiaohu <xuxiaohu@huawei.com>, Donald Eastlake <d3e3e3@gmail.com>, "trill@ietf.org" <trill@ietf.org>
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Subject: Re: [trill] Fwd: Mail regarding draft-ietf-trill-over-ip
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On 5/5/2015 9:39 AM, Templin, Fred L wrote:
> Hi Joe,
..
>> IP in UDP adds only port numbers and an Internet checksum.
>>
>> That doesn't address fragmentation; if outer fragmentation is assumed,
>> IPv4 needs to be rate-limited to avoid ID collisions and the Internet
>> checksum is insufficient to correct those collisions.
> 
> Right - that is why we have GUE. But, when these functions are not
> needed GUE can perform header compression and the result looks
> exactly like IP in UDP.

That seems impossible.

The outer IP header indicates UDP as next-protocol, and GUE based on the
port number.

You can't then compress the GUE header to nothing. You still need at
least one bit somewhere to indicate "compressed GUE header", and there's
nothing left.

And no, I don't think "compressed GUE" qualifies as an independently
useful service that warrants a separate UDP port.

Joe

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