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

Ryuji Wakikawa <ryuji.wakikawa@gmail.com> Tue, 14 April 2009 05:46 UTC

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From: Ryuji Wakikawa <ryuji.wakikawa@gmail.com>
To: "Koodli, Rajeev" <rkoodli@starentnetworks.com>
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Date: Tue, 14 Apr 2009 01:47:32 -0400
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Cc: netlmm@ietf.org
Subject: Re: [netlmm] Consensus call: RFC5107 based DHCP message interceptat MAG
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Hi Rajeev,

On 2009/04/10, at 17:50, Koodli, Rajeev wrote:

>
> Thanks.
>
> I think it is better to keep the LMA solely in charge of the DHCP,  
> and use LMA - MAG signaling for state updates. It also simplifies  
> the matter during handovers (how does the new MAG get the state  
> synchronized, without MN involving in signaling? Does the MN have to  
> send DHCP messages at each handover?).

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).

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:vidyan@qualcomm.com]
> Sent: Thu 4/9/2009 11:11 PM
> To: Koodli, Rajeev; netlmm@ietf.org
> 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: netlmm-bounces@ietf.org [mailto:netlmm-bounces@ietf.org] On
>> Behalf Of Koodli, Rajeev
>> Sent: Thursday, April 09, 2009 10:51 PM
>> To: netlmm@ietf.org
>> 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: netlmm-bounces@ietf.org on behalf of Narayanan, Vidya
>> Sent: Thu 4/9/2009 9:48 PM
>> To: netlmm@ietf.org
>> 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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>
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