Subject: Re: [SIP] Proxy initiating a BYE

From: Dvir Oren <[email-masked]>
Date: Tue, 1 Aug 2000 12:10:43 +0300 (IDT)

Jonathan Rosenberg writes ("Re: [SIP] Proxy initiating a BYE"):

> application server acting as a B2BUA. See the 3pcc draft for some ideas
> on how this works.

I've readh through the 3pcc draft, and find that there is one
characteristic missing.  The second example (click-to-dial) assumes
sount out-of-band mechanism for a user to initiate a call using the
3pcc (in the example it was some HTTP application).  I'll quote:

   We assume for purposes of this discussion that the web server is             
   actually an applications server that contains an http interface. In          
   this case, when the user clicks on the URL, the application server           
   knows, through cookies or some other state mechanism, the addresses          
   of the participants to be connected.

How is this done using SIP?  I want UserA to send an INVITE to a 3pcc, 
to which it will send an INVITE to UserB.  This is why I wanted a
proxy.  A proxy will do exactly that.  However, I need some timing
capabilities (such as a calling card that is time limited).  This
means that the "man in the middle" will need to hang up.  An ideal
solution for me would be for the proxy to hang up.  Perhaps what I
need it to signal the UA that it should hang up, and then the end UA
will send the BYE, instead of the proxy.  This will require an
extension to SIP.

I think that for many QoS and similar applications, this issue should
be address more cleanly.

Suppose a proxy controls a firewall to open or close ports for the
RTP.  For some reason the proxy decides that this call should no
longer pass through the firewall.  A nice solution would have been for 
the proxy to somehow initiate the teardown of the call.  The tools
that the RFC provide seem to point to simply closing the RTP and
letting ICMP notify the parties that they can't be reached.

Am I missing something?

-- 
Dvir Oren               <[email-masked]>
Lucid VON Ltd.     <http://www.lucidvon.com>
9 Saloniki St.,        Tel-Aviv       Israel
Tel:  +972 3 644 3038  Fax:  +972 3 644 3039

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---

From: Hisham Khartabil <[email-masked]>
Date: Tue, 01 Aug 2000 16:01:26 +0300

> will send the BYE, instead of the proxy.  This will require an

I think what you are refering to is some sort of a SIP Controller
(Application Server with parlay interface, for example) that would have UA
capabilities (actually, it would have to be a UA).  As Jonathan said, proxies
don't initiate requests.

The SIP controller would have a timer and send BYEs to both parties once the
timer has expired.

> letting ICMP notify the parties that they can't be reached.

If you are tallking about a SIP Proxy, then I believe what you have described
above is not a function of it.

---

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 04 Aug 2000 03:16:05 -0400

Dvir Oren wrote:
> proxy.  A proxy will do exactly that.

No, a B2BUA will do exactly that. A proxy never *initiates* a new
request. The difference between initiate and proxy is that (1) the via
headers are reset, (2) the contact header is set to the initiator, (3)
possibly other things, but at least 1 and 2.

>  However, I need some timing
> means that the "man in the middle" will need to hang up.

Perfectly fine thing to do in a B2BUA. 

-Jonathan R.

-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
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