Hi Brett,

Since RFC gives first reliable response special treatment (due to
initial RSeq value).
Can we say:
If first reliable response of a dialog is not acknowledged then we can't
send any provisional/final response to UAC even if they are part of
different dialog.
Once the first reliable provisional response is PRACK'd then B2BUA/Proxy
can send subsequent reliable responses of same or different
dialog(provided another dialog's first reliable response is already
complete).

Another question:
When we say reliable responses are acknowledged then do we just meant
PRACK or PRACK & its 200OK ?

Thanks,
Puneet

-----Original Message-----
From: Brett Tate [mailto:[email protected]] 
Sent: Friday, June 29, 2012 4:59 PM
To: Kumar, Puneet (Puneet); [email protected]
Subject: RE: RFC 3262 + Forking

> So as per above 3262 text shown above :
> 
> Can B2BUA send the second reliable 180(as shown 
> in red above) to UA-A even though this second 180 
> will be part of different dialog ?

Yes.  The following section 3 quote explains why the special treatment
applies to the first reliable response for each dialog.  From a UAC
perspective since the UAC received 180 responses for different dialogs,
it is irrelevant if the actual forking occurred because of a B2BUA or
proxy.  Note that the initial sequence number is unique to each dialog.

"The first reliable provisional response receives special treatment
because it conveys the initial sequence number.  If additional reliable
provisional responses were sent before the first was acknowledged, the
UAS could not be certain these were received in order."


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