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

[Haruki Izumikawa <[e-mail]>]

Dear Salvatore,

 > I completely agree with Paul, a SIP mobility solution should consider
 > also the MSRP and
 > in general TCP scenario.
 > In the voice or video scenario (using rtp) a few dropped packets could
 > be acceptable even
 > not noticed at all.
 > However using MSRP or in general TCP the scenario several issue should
 > be considered,
 > for example:
 > - the time to setup a new TCP connection (this especially in the
 > cellular world takes time several seconds)
 > - which messages or packets retransmit
 > - how avoid duplications or even retransmission of the same data

Thank you for pointing out the controversial issues. I have recognized 
the necessity and the importance of the support for the general TCP 
scenario (incl. the MSRP). I just think that make-before-break switching 
(handoff) can be one of the solutions to deal with duration taken to 
setup a new TCP connection...  The other two should be also solved in 
some way.

Rgds,

Haruki



Salvatore Loreto wrote:
> Paul Kyzivat wrote:
>> Haruki Izumikawa wrote:
>>   
>>>  > And related to that - what about non-RTP media?
>>>  > This same scenario is applicable to less conventional
>>>  > media, such as IM. While technically it is possible
>>>  > to follow the pattern you have outlined to establish
>>>  > bicast MSRP, the identification of duplicate messages
>>>  > will require a different solution.
>>>
>>> [HI] I think the bicasting solution is needed for realtime multimedia 
>>> streams in which re-transmission cannot be acceptable. Therefore, I 
>>> don't know some services such as IM or file transfer using MSRP need 
>>> bicasting support. In fact, I haven't considered the concern you pointed 
>>> out. I'm going to have to weigh this concern more carefully. Thank you 
>>> for bringing this matter up.
>>>     
>>
>> I guess it depends on what you mean by "acceptable".
>> If you move from wifi to cellular access while IMing, I will not be 
>> happy if some IMs from you are dropped or duplicated.
>>
>> In fact, I think this is more noticable for IM than for voice. With 
>> voice a few dropped packets may cause a "glitch" but probably will not 
>> create a significant loss of information. But a single dropped IM can be 
>> a large loss of information.
>>
>> And now people are talking about using MSRP for real time text as well.
>>
>> So while it is perhaps of lower priority and interest, I think media 
>> such as MSRP are worthy of some consideration.
>>   
> I completely agree with Paul, a SIP mobility solution should consider 
> also the MSRP and
> in general TCP scenario.
> In the voice or video scenario (using rtp) a few dropped packets could 
> be acceptable even
> not noticed at all.
> However using MSRP or in general TCP the scenario several issue should 
> be considered,
> for example:
> - the time to setup a new TCP connection (this especially in the 
> cellular world takes time several seconds)
> - which messages or packets retransmit
> - how avoid duplications or even retransmission of the same data
> 
> regards
> Sal

-- 
Haruki Izumikawa
KDDI R&D Laboratories

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