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

[Joe Touch <[e-mail]>]

On 5/5/2015 11:53 AM, Tom Herbert wrote:
> On Tue, May 5, 2015 at 11:47 AM, Templin, Fred L
> <[e-mail]> wrote:
>> Hi Joe,
>>
>>> -----Original Message-----
>>> From: Joe Touch [mailto:[e-mail]]
>>> Sent: Tuesday, May 05, 2015 11:26 AM
>>> To: Templin, Fred L; Xuxiaohu; Donald Eastlake; [e-mail]
>>> Cc: [e-mail]; [e-mail]; [e-mail]
>>> Subject: Re: [trill] Fwd: Mail regarding draft-ietf-trill-over-ip
>>>
>>>
>>>
>>> On 5/5/2015 11:04 AM, Templin, Fred L wrote:
>>>> Hi Joe,
>>>>
>>>>> -----Original Message-----
>>>>> From: Joe Touch [mailto:[e-mail]]
>>>>> Sent: Tuesday, May 05, 2015 10:54 AM
>>>>> To: Templin, Fred L; Xuxiaohu; Donald Eastlake; [e-mail]
>>>>> Cc: [e-mail]; [e-mail]; [e-mail]
>>>>> 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 version field in both IPv4 and IPv6 have that bit set to 1. If GUE
>> then deems that bit to indicate "direct IP encapsulation, then there
>> is no need for a GUE header of length greater than 0.
>>
>> You may say that future IP protocol versions might not have that bit
>> set in the version field. But, the version bits for IPv4 and IPv6 will
>> never change (by definition) and we do not see a new IP protocol
>> version replacing IPv4 or IPv6 on the near-term horizon.
>>
>> Even if a new IP protocol version emerged with the "direct IP
>> encapsulation" bit set to 0, that version can still be accommodated
>> by GUE. It's just that direct encapsulation cannot be used and a
>> non-zero-length GUE header is needed.
>>
> Or just define a simple version translation as part of encapsulation.
> So for IPv8:
> 
> 0x1000->0x0101 on encapsulation
> 0x0101->0x1000 on decapsualtion

And what happens to 0x0101 WHEN it shows up?

You need more patterns than you have because IP is allowed to use any of
them.

That's why you need an extra bit, and that's why you can't assume these
bits are "yours".

Joe