Re: [netlmm] Consensus call: RFC5107 based DHCP message interceptat MAG

[Sri Gundavelli <[e-mail]>]

On Tue, 14 Apr 2009, Koodli, Rajeev wrote:

>
> Hi,
>
> there seem to be some loose ends here. The reasoning given for the need to intercept DHCP messages at MAG was to allow for the state consistency between LMA and MAG. Your e-mail below suggests no such actions are necessary (at least for the DHCP-relay functionality). Sri's e-mail (as a reply to my previous e-mail) suggests using DNAv4 on the MN so that the MAG can synchronize the state:
>

Ok. Probably the way we both said it. Lets look at what we both said.

1. About DNAv4. The mobile node's typically apply DNAv4 for detecting
on-link presence. If DNAv4 procedure is trigerred, the MN will detect
the same link and will not perform DHCP specifically due to handoff
event. If DNAv4 procedure is not used, still the link that we present
from the perspective of layer-2, DHCP, default-router is consistent
and the MN will not detect a change. This is also the HO transparency
that Ryuji was talking about, it needs to be looked at in the context
of the DNA used or not used.

2. DNAv4 procedure has no bearing on the network. Its for the MN
to detect a link change. On the network, for the MAG to trigger
PMIP signaling, the MN-Attach, acces auth, a trigger from the network,
or even a CT from the prev MAG wil trigger the MAG to perform PMIP
signaling.

3. MAG will certainly synchroized the state from LMA through PMIP
signaling, only after each handoff. The MAG will not be in path for
subsequent DHCP events after handoff. This option will enable the MAG
to register itself to be in path for all messages. If a MN releases
an address, if the LMA recycles the address and allocates to some
other node. We will have two host routes one from the MAG1 to LMA,
LMA to MAG2. The kind of inconsistent states can be avoided, by
ensuring the node that created the routing state is aware of all
the DHCP transactions.



Sri




> "The mobile after handoff should trigger DNAv4 procedures for detecting
> onlink presence. MAG would complete the PMIP signaling and obtain all
> the state from the LMA, during this time."
>
> If we need DNAv4 for MAG and LMA synchronization, why could we not rely on LMA - MAG signaling in the first place?
>
> It would be good to have some clarity (and the corresponding text for revision) :-)
>
> Regards,
>
> -Rajeev
>
>
> ________________________________
>
> From: Ryuji Wakikawa [mailto:[e-mail]]
> Sent: Tue 4/14/2009 9:01 AM
> To: Koodli, Rajeev
> Cc: [e-mail]
> Subject: Re: [netlmm] Consensus call: RFC5107 based DHCP message interceptat MAG
>
>
>
> Hi Rajeev,
>
> On 2009/04/14, at 11:23, Koodli, Rajeev wrote:
>
>>
>> Hi Ryuji,
>>
>>> MN does not send any DHCP messages at handover, because HO is
>>> transparent to MN.
>>> When MN renew the  IP address, the new MAG (DHCP-relay) will
>>> intercept
>>> the packets with RFC5107 or promiscuous interception to sync the
>>> state
>>> (verify the IPv4 leasing time. DHCP relay does not maintain any
>>> states
>>> of DHCP clients).
>>
>> Until the MN sends any DHCP messages, the new MAG will not have the
>> consistent DHCP state then right?
>
> The general DHCP relay does not keep any states of MN. All the states
> are managed at DHCP server.
> We don't need to introduce any new states on DHCP relay for PMIP.
>
> In PMIP, we have decided to manage the address assignment by LMA
> (PMIP) and use DHCP to deliver the assigned address to MN.
> To co-operate DHCP and PMIP, we don't need any MN's actions to keep
> consistency of DHCP states.
>
>> Also, all the MAGs should be configured with this support.
>
> Yes, all the MAGs has to be either DHCP relay or server.
>
> regards,
> ryuji
>
>>
>>
>> Thanks,
>>
>> -Rajeev
>>
>>
>> regards,
>> ryuji
>>
>>
>>
>>
>>> Having said that, I am okay with keeping the optional mechanism, *as
>>> long as*
>>>
>>> 1. we describe the two choices we have - LMA being the sole DHCP
>>> node on the network side, which is mandatory, and the optional
>>> mechanism of MAG-on-path for DHCP
>>>
>>> 2. Clearly state what needs to be done for handovers for the
>>> optional mechanism, in addition to what is the purpose of the
>>> optional mechanism (it could not be just informative).
>>>
>>> These have to be captured, say in separate paragraphs.
>>>
>>> -Rajeev
>>>
>>>
>>>
>>> ________________________________
>>>
>>> From: Narayanan, Vidya [mailto:[e-mail]]
>>> Sent: Thu 4/9/2009 11:11 PM
>>> To: Koodli, Rajeev; [e-mail]
>>> Subject: RE: [netlmm] Consensus call: RFC5107 based DHCP message
>>> interceptat MAG
>>>
>>>
>>>
>>> Hi Rajeev,
>>> If the MAG does not intercept DHCP messages, it will be unaware of
>>> any DHCP state changes (e.g., lease termination, IP address change/
>>> release, etc.) for the MN.  We don't have mandatory defined behavior
>>> in the LMA to avoid such potential state changes.  So, short of
>>> using RFC5107, the MAG needs to intercept DHCP messages to figure
>>> this out.
>>>
>>> I also want to highlight the difference between using and not using
>>> RFC5107 behavior.  The use of RFC5107 will allow the MAG to do
>>> normal forwarding.  If not, the MAG will need to inspect on the
>>> {destination IP address, protocol, port} tuple to trap the DHCP
>>> packets destined to the server.
>>>
>>> Vidya
>>>
>>>> -----Original Message-----
>>>> From: [e-mail] [mailto:[e-mail]] On
>>>> Behalf Of Koodli, Rajeev
>>>> Sent: Thursday, April 09, 2009 10:51 PM
>>>> To: [e-mail]
>>>> Subject: Re: [netlmm] Consensus call: RFC5107 based DHCP message
>>>> intercept at MAG
>>>>
>>>>
>>>> Hi Vidya,
>>>>
>>>> question for my clarification: why does the MAG need to intercept
>>>> DHCP
>>>> messages?
>>>>
>>>> Thanks,
>>>>
>>>> -Rajeev
>>>>
>>>>
>>>> ________________________________
>>>>
>>>> From: [e-mail] on behalf of Narayanan, Vidya
>>>> Sent: Thu 4/9/2009 9:48 PM
>>>> To: [e-mail]
>>>> Subject: [netlmm] Consensus call: RFC5107 based DHCP message
>>>> intercept
>>>> at MAG
>>>>
>>>>
>>>>
>>>> An issue has been raised on the inclusion of the DHCP Server
>>>> Identifier
>>>> Override sub-option (specified in RFC5107) as a means for the MAG to
>>>> intercept the MN's DHCP messages sent to the DHCP server.  This
>>>> option
>>>> allows the relay (MAG) to act like the DHCP server and more directly
>>>> get the MN to even address the RENEW DHCP requests to itself, so
>>>> that
>>>> the MAG can include the Relay Agent option in those messages as
>>>> well.
>>>> Without this option, the relay in the MAG would need to intercept
>>>> all
>>>> DHCP messages.
>>>>
>>>> In PMIPv6, all packets from the MN will go through the MAG - from an
>>>> implementation perspective, my interpretation is that the use of
>>>> RFC5107 is likely to make a difference in the extent of hardware
>>>> based
>>>> forwarding that is made feasible in the MAG.  Otherwise,
>>>> functionally,
>>>> the MAG should be able to intercept all DHCP messages even without
>>>> this
>>>> option.
>>>>
>>>> The issue raised is primarily from an IPR perspective - please see
>>>> the
>>>> following link for the IPR terms associated with RFC5107:
>>>>
>>>> https://datatracker.ietf.org/ipr/124/
>>>>
>>>> I would like to hear WG input on whether you prefer to keep the
>>>> option
>>>> in the document or take it out.  If you can provide an explanation
>>>> for
>>>> the choice you make (IPR and/or technical), it will be useful.
>>>>
>>>> Please respond to the list by April 15th, 2009.
>>>>
>>>> Thanks,
>>>> Vidya <as co-chair>
>>>> _______________________________________________
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>>>>
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