On Thu, 2009-11-19 at 11:49 +0530, hanifa.mohammed wrote:
> Hi all,
> 
>     It is very common that a single UA stack, in a device, shall be used by 
> many users. In that case,
> shall all users use a common instance-id? Will it give any trouble, in real 
> time?
> 
> Pl clarify whether instance-id is an user configuration or UA configuration.
> 
> Below is an excerpt from RFC5626, that says that instance ID is device 
> specific and not user specific.
> 
> "The instance ID MUST NOT change as the device moves from one network to 
> another."

First, note that the sentence you quoted does not refer to "user" at
all.

The central question is what is a "device", from the point of view of
the user.  A simple case is a desk telephone, which may have several
"lines", each with a different AOR.  Because the user *thinks* of the
telephone as a single device, the registrations and other operations it
carries out should use a single instance-id.

A software-based telephone application running on a single-user computer
is in a similar situation; the user thinks of it as a single "device",
so it uses one instance-id.

Now consider two different software-based telephone applications running
on a computer.  If they serve two different people, or if they are in
now way coordinated with each other, they must use two different
instance-ids.

It is also conceivable that a single software application could function
as *two* telephones, one for each of two different users (given the
necessary hardware devices).  In that case, the application needs to
partition its activities into two groups, one for each user, and use a
separate instance-id for each group.

Dale


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