Christer,
Sorry, when I said "mis-interpret what they see as forking" I meant to
refer to serial forking, which is of course a form of forking. So
there's no mis-interpretation (except mine!).
But anyway the thought was that by providing a way to explicitly release
an early media stream the 199 could enable a "middle box" (SBC) that
today blocks serial forking, to support it. This is one of the use
cases Hadriel mentioned.
tim
________________________________
From: Christer Holmberg [mailto:[EMAIL PROTECTED]
Sent: Tuesday, November 18, 2008 4:14 PM
To: Dwight, Timothy M (Tim); IETF SIP List
Subject: RE: [Sip] 199 Open Issue: UAS sending 199
Hi Tim,
>My opinion is that 199 shouldn't be restricted to cases
involving forking, since some of its utility lies in
>mitigating the behavior of middle boxes that mis-interpret what
they see as forking.
I am not sure I understand. Could you please clarify?
>Is it possible to define a simpler version of alternative #4,
giving general guidance as to when a 199 may be issued
>and being prescriptive about what the recipient is to do upon
its receipt?
Personally I think it would be very difficult to come up with
something general and useful.
Regards,
Christer
________________________________
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Christer Holmberg
Sent: Tuesday, November 18, 2008 1:17 PM
To: IETF SIP List
Subject: [Sip] 199 Open Issue: UAS sending 199
Hi,
The main open issue in the 199 draft at the moment is
when a UAS sends 199 - IF a UAS sends 199.
The alternative proposals I have at the moment are
described below (can also be found in the slides I was supposed to
present yesterday).
1. UAS never sends 199:
In this case only forking proxies/B2BUA would send 199.
2. UAS always sends 199:
The issue with this alternative is that 199 would be
sent even if no forking has occurred - which can be assumed to be the
case in a large percentage of all calls.
3. UAS sends 199 if forking proxy does not support
199:
With this alternative the forking proxy would have to
insert an indicator that it supports 199.
Also, the UAS may not know whether it is the forking
proxy closest to the UAS that has inserted the indicator. This may not
be a big issues, since I assume in most forking cases there will only be
one forking proxy in the signalling path.
4. UAS sends 199 once procedures have reached a
certain state
With this alternative 199 would not be sent until
certain actions have taken place on an early dialog
Example: preconditions have been indicated as met
Example: SDP answer has been sent
The issue is that one would always have to specify at
what point of different procedures 199 would be sengt.
5. UAC and UAS negotiate sending of 199 once the
early dialog has been established:
With this alternative that UAC would tell the UAS that
forking has occurred (could this be useful information also for non-199
procedures?), and that it wants 199 to be sent.
The issues with this alternative is that it may require
additional signalling (unless PRACK/UPDATE won't be sent for other
reasons) to inform the UAS that forking has occurred.
Other alternatives?
NOTE: Robert S also raised an issue on what Require: 199
means. But, I think that outcome of that issue may depend on what way
forward we choose for the issue in this mail.
Regards,
Christer
_______________________________________________
Sip mailing list https://www.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [EMAIL PROTECTED] for questions on current sip
Use [EMAIL PROTECTED] for new developments on the application of sip
