Re: Dual registration without Outbound

Dean Willis wrote:
> 
> On Oct 15, 2008, at 3:51 AM, Elwell, John wrote:
> 
>>
>> "Instance ID MUST NOT change as the device moves from one network to
>>   another."

I've always viewed this as one worthwhile objective, but that there may 
be conflicting objectives that lead to multiple instance ids.

For instance, if I sell my device to Dean, he may not want it to have 
the same instance id it had when it was mine.

Or I may want to change ids so that it appears to others that I have two 
devices rather than one. (Maybe someone will try to correlate my 
location to the device I am using, and I want to throw them off.)

And with soft devices it is very subjective when what I have is one 
logical device or several.

I think all we can do is hope that the same instance id is used when the 
user is willing for some continuity of device identity to be perceived.

Trying to register the "same UA" concurrently with two different 
instance ids in an attempt to get parallel forked call attempts via 
different networks is creative but a bit ugly. For one thing its hard in 
general to guarantee that the two will be parallel forked. And the UA 
will have to attempt to correlate the two in order to realize they are 
the same and so process correctly. An SBC between the forking proxy and 
the UA is likely to disturb the CallID, the From, and the caller's 
Contact address. With those messed up the correlation will get difficult.

	Thanks,
	Paul
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