Re: [MEXT] GRE support in DSMIPv6 - AD review

[Henrik Levkowetz <henrik at levkowetz.com>]

Hi,

On 2009-01-15 19:32 Vijay Devarapalli said the following:
> Hi Pasi, Hesham,
> 
> The TLV header was specified in the DS-MIPv6 document after rather a
> long and acrimonious debate on the former MIP6 mailing list. There were
> atleast two consensus calls that were run at that time. Anytime you have
> a UDP header with IPv4/IPv6/GRE header following it, you need the TLV
> header. At that time, there were folks arguing for using GRE
> encapsulation with MIPv6 also. PMIPv6 IPv4 support was not the only
> scenario for the TLV header. We are overturning that consensus now.
> Maybe folks who were arguing for the TLV header with DS-MIPv6, are
> either busy/not looked at this thread yet/or not on the MEXT mailing
> list/etc.. :)
> 
> Moving the TLV header into a separate document at this point would
> impact draft-ietf-netlmm-pmip6-ipv4-support. I don't think the TLV
> header document can be standardized fast enough for
> draft-ietf-netlmm-pmip6-ipv4-support to advance. One option would be to
> move the TLV header and the text that describes how to negotiate it, to
> either draft-ietf-netlmm-pmip6-ipv4-support or
> draft-ietf-netlmm-grekey-option. 
> 
> My suggestion would be to leave the TLV header in the DS-MIPv6 document.
> Have some text that says the following. If UDP encapsulation is used
> with DS-MIPv6 port, there could be IPv4, IPv6, GRE or some other header
> that might follow the UDP header. If there is anything other than the
> IPv4 or IPv6 header, the TLV header would be required. The use of GRE or
> some other protocol after the TLV header is not specified and is out of
> scope in the DS-MIPv6 document.

That would work for me.  I'd very much like to see the TLV header itself
kept; the reason is that if something else (GRE or whatever) than an IP
header follows the UDP header, there isn't a clear and obvious way of
dynamically distinguishing *what* that something else is, unless the
TLV header is there.  Ripping it out completely would leave the
specification less ready for extension than otherwise, which would be
unfortunate if we already know that there are needs for extension.

One thing in the -05 and -06 drafts which surprised me when looking at
them now was the value assignments for the TLV type field -- I'd expected
the use of already-defined protocol numbers here, in a similar manner to
what's in Section 3.3 of RFC 3519, rather than a new registry.  But there
are maybe things I've forgotten from our earlier discussion which makes
a new type number space necessary.


	Henrik



> 
> Vijay 
> 
> 
>> -----Original Message-----
>> From: mext-bounces at ietf.org [mailto:mext-bounces at ietf.org] On 
>> Behalf Of Pasi.Eronen at nokia.com
>> Sent: Thursday, January 15, 2009 3:54 AM
>> To: hesham at elevatemobile.com; mext at ietf.org
>> Subject: Re: [MEXT] GRE support in DSMIPv6 - AD review
>>
>> Hesham,
>>
>> I would strongly suggest moving the whole TLV header text to the
>> separate GRE document.
>>
>> In particular, if you assign a number for GRE in this document,
>> you either need to describe how it works here, or have a normative
>> reference to the NETLMM spec.
>>
>> Best regards,
>> Pasi
>>
>>> -----Original Message-----
>>> From: ext Hesham Soliman [mailto:hesham at elevatemobile.com] 
>>> Sent: 14 January, 2009 14:23
>>> To: mext at ietf.org
>>> Cc: Eronen Pasi (Nokia-NRC/Helsinki)
>>> Subject: GRE support in DSMIPv6 - AD review
>>>
>>> Folks, 
>>>
>>> Part of Pasi's review for DSMIPv6 was a comment on the lack of
>>> specification for GRE support in the spec. He said it was vastly
>>> under-specified, no details on the tunnelling, setting of different
>>> parts of the GRE header ...etc.
>>>
>>> I suggested that we don't explicitly mention GRE in the spec but we
>>> keep the TLV tunnelling format and reserve the numbers for NETLMM to
>>> specify exactly how it will be used in a separate document. I think
>>> you would agree that this is largely driven by NETLMM needs and we
>>> shouldn't specify the details in MEXT. Pasi was ok with that.
>>>
>>> Please express your opinion on this soon because Pasi's comments are
>>> the last comments for the draft and I want to handle them by Monday
>>> at the latest.
>>>
>>> Please avoid discussing the merits of GRE....etc, the question is:
>>>
>>> Are there any objections to removing explicit references to GRE
>>> while reserving the numbers in the TLV header for it to be specified
>>> clearly in NETLMM?
>>>
>>> Thanks,
>>>
>>> Hesham
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