Re: [Sipping] Request for Open discussion about SIP mobility

[Stefano Salsano <[e-mail]>]

Elwell, John wrote:
> [JRE] This is just another instance of the general problem of B2BUAs
> (e.g. SBCs) providing functionality to compensate for endpoints that do
> not fully support fairly basic mechanisms in SIP, namely re-INVITE in
> this particular case. It is a fact that such middleboxes do exist, and
> we can argue about whether they exist for good reasons or not. However,
> does the IETF really want to specify such work-arounds for these
> problems, rather than trying to address the fundamental problem?
> 

Dear John,

it is not only a problem of specifying a work-around for "basic" 
endpoints (though this may be a useful "side-achievement"...)

In my opinion there are some conceptual reasons why we should provide 
the possibility to handle terminal mobility on the side of the Mobile 
Device, rather then on the side of the correspondant node. The user of 
the Mobile Device has a strong interest in the reliability and 
performance of this mobility, and may want to control it better than 
relying on the CN capabilities.

And as I pointed out, there are some performance issues that may require 
an improvement with respect to the curent re-INVITE mechanisms.

Best regards,
Stefano

> John
> 
>> 2) Performance issues: the current solution is not very well 
>> suited for 
>> a seamless handover, comparable in performance with cellular 
>> networks. 
>> Mechanisms like bi-casting could improve the performance.
>>
>> Comments are welcome!
>>
>> Best regards,
>> Stefano
>>
>>> Ashutosh Dutta wrote:
>>>> Haruki,
>>>>        I would actually put Shacham et al.'s draft into 
>> session mobility 
>>>> category rather than service mobility since it involves 
>> transferring an 
>>>> existing session from one device to another device. While 
>> there is a 
>>>> need for fast session transfer between devices, fast-handoff for 
>>>> SIP-based terminal mobility needs to be looked into as 
>> well, where the 
>>>> existing session continues on the same device after the 
>> handoff (the 
>>>> device could be single homed or multi-homed).
>>>>
>>>> Realizing the need for fast-handoff for SIP-based terminal 
>> mobility, 
>>>> subsequent to the paper that you had cited below, we did 
>> publish few 
>>>> other papers later on that looked into some possibilities 
>> of supporting 
>>>> fast-handoff for SIP-based terminal mobility. Let me cite 
>> those below. I 
>>>> am also aware of few other papers supporting SIP-based 
>> terminal mobility 
>>>> and fast-handoff as well.
>>>>
>>>> 1) A. Dutta, S.Madhani, H. Schulzrinne, O. Altintas, W. 
>> Chen, "Optimized 
>>>> Fast-handoff Schemes for Application Layer Mobility 
>> Management,"  ACM 
>>>> MC2R November 2002
>>>>
>>>> 2) P-Y Hsieh, A. Dutta, H. Schulzrinne,  "Application 
>> Layer Mobility 
>>>> Proxy for Real-time communication," 3G Wireless 2003, San 
>> Francisco, CA
>>>> 3) A. Dutta, S. Madhani, W. Chen, O. Altintas, H. Schulzrinne, 
>>>> "Fast-handoff Schemes for Application Layer Mobility 
>> Management," PIMRC 
>>>> 2004, Barcelona, Spain
>>>>
>>>>
>>>> While there are variations of fast-handoff techniques for 
>> network layer 
>>>> mobility (e.g., FMIPV6, HMIPv6, FPMIPv6), I think it is 
>> probably a good 
>>>> idea to investigate if existing techniques can support 
>> fast-handoff for 
>>>> SIP-based terminal mobility. This need becomes more apparent if a 
>>>> carrier or any application service provider does not want 
>> to deploy any 
>>>> MIP variants to support purely SIP-based applications.
>>>>
>>>> Regards
>>>> Ashutosh


-- 
*******************************************************************
Stefano Salsano
Dipartimento Ingegneria Elettronica
Universita' di Roma "Tor Vergata"
Via del Politecnico, 1 - 00133 Roma - ITALY

http://netgroup.uniroma2.it/Stefano_Salsano/

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