[SIPForum-techwg] Question about early dialog

[Robert Sparks]

Yes, you create an early dialog for each of the remote tags you receive.

Each of these early dialogs may be involved in subsequent signaling  
or media
before a 200 OK happens (preconditions or early media). You don't  
know until
you get that 200 which one will ultimately complete, so you must keep  
them all
going.

And you may well get more than one 200 (its a race condition, but it  
can occur).

RjS

On Nov 7, 2007, at 9:51 AM, mike xu wrote:

> Hi,
>
> In RFC3261 section 13.2.2.1, it said
>    "Zero, one or multiple provisional responses may arrive before  
> one or
>    more final responses are received.  Provisional responses for an
>    INVITE request can create "early dialogs".  If a provisional  
> response
>    has a tag in the To field, and if the dialog ID of the response  
> does
>    not match an existing dialog, one is constructed using the  
> procedures
>    defined in Section 12.1.2."
>
> So, does it mean that when receive multiple 1xx response (with
> different to-tag), I shall create multiple early dialog for each 1xx
> response? Since only one 200 OK will be accepted in the end, are these
> early dialogs really necessary?
>
> Thanks,
> Mike
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