Re: [MEXT] using MR-HA tunnel vs. combining BU // Re: WGLC for draft-ietf-mext-nemo-pd-01.txt

["fan zhao" <[e-mail]>]

Hi Alex,

Please see below.

On Thu, Dec 11, 2008 at 9:30 AM, Alexandru Petrescu
<[e-mail]> wrote:
> Ryuji Wakikawa wrote:
>>
>> Hi Julien and Yungui,
>>
>> Actually, it's not only 3 round trip and is not optimization problem..
>> This is a big issue of DHCP-PD.
>>
>> Let me explain the issue clearly.
>>
>> According to the NEMO-DHCP-PD spec, before receiving a prefix,
>> a mobile router must create a tunnel with its HA.
>
> Not sure about this necessity?  Where does this nemo-dhcp-pd draft say so?
Please see section 3.2.  Use of MR-HA tunnel for DHCPv6 messages.

>
> If one considers the MR to co-locate a DHCP Relay with a DHCP Client
> (section 3.3) then the Relay would unicast non-tunnelled with the
> HA-DHCPServer (not multicast, and not tunnel) the DHCP messages.
>
>> For this purpose, the mobile router needs to act as a RFC3775
>> compliant mobile host before starting DHCP-PD.  Why? If there is no
>> prefix, the mobile router cannot sends a NEMO-BU (i.e. R-flag set) to
>> its Home Agent.
>
> Well the MR can send a BU with R-flag set without having a prefix allocated
> to it via DHCP-PD, by considering the NEMO implicit mode.  IT is sufficient
> for the HA to know the prefix it is allocated to that MR.
I think Ryuji has addressed this in his previous emails.

>
> It is obvious that we disagree on the sequence of the exchanged messages
> (DHCP, BU/BAck) and I think we need to draw a diagram with the message
> exchanges that we consider.  I could draw mine.
Please do. Thanks a lot.

Sincerely,
fan

>
> Alex
>
>  If there is no valid prefix for the mobile router, HA
>>
>> returns BA with "Invalid Prefix" status value which is treated as the
>> fatal error in RFC3963.
>>
>> Well, RFC3963 allows for a mobile router to act as a mobile host, but
>> we didn't assume that a mobile router switches its mode between
>> RFC3775-mobile-host and RFC3963-mobile-router dynamically.
>>
>> For instance, RFC3963 said in section 6.2,
>> "If the Home Agent has a valid binding cache entry for the Mobile
>> Router, and if the Binding Update has the Mobile Router Flag (R) set
>> to a value different from that in the existing binding cache entry,
>> then the Home Agent MUST reject the Binding Update and send a Binding
>> Acknowledgement with status set to 139 (Registration type change
>> disallowed). However, if the Binding Update is a de-registration
>> Binding Update, the Home Agent ignores the value of the Mobile Router
>> Flag (R)."
>>
>> At the end, how the boostrapping goes?
>>
>> 1. MR acts as a MN and sends MIP6-BU (Rflag unset) to establish a
>>   tunnel for DHCP-PD
>> 2. MR starting DHCP-PD
>> 3. After DHCP-PD completion, MR de-registers the RFC3775-binding
>> 4. MR sends NEMO-BU (R-flag finally set) for its mobile network prefix
>>   acquired by DHCP-PD
>>
>> I don't think this is right way to go....
>>
>> I now changed my mind that the use of BU/BA is more straightforward
>> for NEMO prefix delegation.
>>
>> ryuji
>>
>>
>> On 2008/12/11, at 10:50, Julien Laganier wrote:
>>
>>> We had this discussion for a long time abd it has concluded some time
>>> ago already: WG consensus is to use DHCP PD.
>>>
>>> (w/o questioning the value of optimizing RTTs for a procedure which
>>> isn't in a critical path, e.g., handover)
>>>
>>> --julien
>>>
>>> On Thursday 11 December 2008, Yungui Wang wrote:
>>>>
>>>> Hello
>>>>
>>>> Here is one comment about using MR-HA tunnel for DHCP-PD.
>>>>
>>>> In this draft, the MR registration processing needs 3 round trip
>>>> between MR and HA. i. BU to HA; (getting and binding MR_HoA)
>>>> ii. DHCPv6 message over MR-HA tunnel. (getting MNP)
>>>> iii. BU to HA; (binding MNP)
>>>> While, if PD is combined within BU, it is only 1 round trip.
>>>>
>>>> From implementation of viewpoint, the later seems well done prior of
>>>> the former. Maybe I have lost something, can anyone tell me the story
>>>> why we gave up the latter in the new version? Thanks.
>>>>
>>>> B.R.
>>>> Yungui
>>>>
>>>>
>>>> ----- Original Message -----
>>>>  From: marcelo bagnulo braun
>>>>  To: mext ; Julien Laganier ; Ralph Droms
>>>>  Sent: Tuesday, November 04, 2008 8:02 PM
>>>>  Subject: [MEXT] WGLC for draft-ietf-mext-nemo-pd-01.txt
>>>>
>>>>
>>>>  Hi,
>>>>
>>>>  We now start the WGLC for:
>>>>
>>>>  DHCPv6 Prefix Delegation for NEMO
>>>>  draft-ietf-mext-nemo-pd-01.txt
>>>>
>>>>  http://www.ietf.org/internet-drafts/draft-ietf-mext-nemo-pd-01.txt
>>>>
>>>>
>>>>  Please send comments about the draft till the November 19.
>>>>
>>>>  Regards, Julien and marcelo
>>>>
>>>>
>>>>  _______________________________________________
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>>>>  https://www.ietf.org/mailman/listinfo/mext
>>>
>>>
>>>
>>> --
>>> --julien
>>>
>>> [ New email address: [e-mail] ]
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