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

Joe Touch <touch@isi.edu> Tue, 05 May 2015 18:26 UTC

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Date: Tue, 05 May 2015 11:26:09 -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 11:04 AM, Templin, Fred L wrote:
> Hi Joe,
> 
>> -----Original Message-----
>> From: Joe Touch [mailto:touch@isi.edu]
>> Sent: Tuesday, May 05, 2015 10:54 AM
>> To: Templin, Fred L; Xuxiaohu; Donald Eastlake; trill@ietf.org
>> Cc: nvo3@ietf.org; int-area@ietf.org; sfc@ietf.org
>> Subject: Re: [trill] Fwd: Mail regarding draft-ietf-trill-over-ip
>>
>>
>>
>> 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.
> 
> Not impossible - Tom Herbert provided the solution:
> 
> http://www.ietf.org/mail-archive/web/int-area/current/msg04593.html

That is allocating bits (or bit patterns) from the IP header.

The solution provided - to check for 0x01 - is incorrect. IP can have
versions that include 0x10 and 0x11.

The only solution would be to say that if the first three bits were 0,
then it's not an IP packet - but that would require reassigning 0x0000
and 0x0001 for GUE purposes.

Although that's possible, I don't see why we would allocate IP versions
to GUE message types.

Joe