Forking INVITE SIP message - regarding

Hello,
   
  Consider the following situation.
   
              Adam wants to call Bob, let’s say that Bob is
registered at three locations, that is, at home, at head
office and at his branch office. Hence, when Adam makes a
call, INVITE request is forked by the proxy and it reaches
all the three destinations. Hence, three 200 OK SIP response
will be sent back to Adam. 
   
              Consider the situation, when Bob’s friends
answer the call at all the three locations at the same time,
what will happen? Either three media channel will be
established between them or which two will be discarded.
   
              Can anyone please clear this?
   
  With regards
  Raj.

 
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Raj wrote:
> Hello,
>    
>   Consider the following situation.
>    
>               Adam wants to call Bob, let’s say that
Bob is registered at three locations, that is, at home, at
head office and at his branch office. Hence, when Adam makes
a call, INVITE request is forked by the proxy and it reaches
all the three destinations. Hence, three 200 OK SIP response
will be sent back to Adam. 
>    
>               Consider the situation, when Bob’s
friends answer the call at all the three locations at the
same time, what will happen? Either three media channel will
be established between them or which two will be discarded.
>    
>               Can anyone please clear this?

While all three locations may ring at once, its unlikely
that all three 
with answer at exactly the same time. As long as one answers
first be a 
second of so, the proxy will cancel the others and they
won't send a 200 
response.

Its only when multiple phones are answered in the small time
window 
where they can't be canceled that you get multiple 200
replies. If that 
happens, its up to Adam's UA to decide what to do. While it
*could* 
conference them all together, a common strategy is simply to
send a BYE 
to all except the first.

	Paul
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