Re: [Sipping] Liaison Statement on offer/answer procedures

[Paul Kyzivat <pkyzivat at cisco.com>]

John,

This is a good point.

It does expose a potentially long window when address changes are 
problematic. I guess if a quick address change is necessary then the 
INVITE, or reINVITE, can be CANCELed.

IMO this is starting to identify an area that could stand to have more 
specification. I guess this sounds like a best practices draft, but its 
still a little fuzzy to me. And I am far from clear whether this is 
tightly connected to the o/a rollback issue.

	Thanks,
	Paul

Elwell, John wrote:
> Paul,
> 
> 
>> -----Original Message-----
>> From: sipping-bounces at ietf.org 
>> [mailto:sipping-bounces at ietf.org] On Behalf Of Paul Kyzivat
>> Sent: 15 May 2008 14:48
>> To: Christer Holmberg
>> Cc: sipping List
>> Subject: Re: [Sipping] Liaison Statement on offer/answer procedures
>>
>> Christer,
>>
>> Saying "you shouldn't do it" to changing contact address or media 
>> address ignores facts of life that may require doing it. This 
>> overlaps 
>> strongly with the session mobility discussion that is 
>> currently going on.
>>
>> Specifically, if a UA is losing possession of its address, or 
>> connectivity via that address, then it will have to do 
>> *something*. If 
>> we are going to say that you shouldn't change the contact 
>> address in a 
>> dialog, and shouldn't change the media address in a media 
>> session, then 
>> we need to specify some alternative.
>>
>> Clearly there are at least two distinct cases here:
>>
>> - there is a desire to switch to a new address, but the old address
>>    can continue to be supported until and unless use of the new one
>>    can be established
> [JRE] So if the contact address changes and we successfully conclude the
> UPDATE transaction, and then the old contact address disappears, it is
> likely that the Via list on the re-INVITE request will have become
> invalidated too, so the final response will not reach the UAC. Correct?
> 
> John
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