[Serusers] RE: Transfer and Conferencing - Please help!

[Bob Carlson]

Thanks a lot for the pointer to Sip Scenario.  It looks like a fantastic
tool.  I will take a look at Asterisk.

Thanks again, Bob

-----Original Message-----
From: Greg Fausak [mailto:greg at addabrand.com] 
Sent: Thursday, November 04, 2004 3:23 PM
To: Bob Carlson
Cc: 'SerUsers'
Subject: Re: [Serusers] RE: Transfer and Conferencing - Please help!

Bob,

I can offer some ideas that might help.
I certainly don't intend to be condescending...

Many of my questions are answered with call traces.
For example, I worked on a bug with REINVITES today.

	http://www.addaline.com/traces/andy_index.html

This is created by using a :

1) switch with port monitoring
2) ethereal (or tcpdump) to grab data
3) sipscenario to format the data into the call trace

A transfer can be done in a few different ways, especially when
you get an IP-PBX involved.  There is a popular one called
Asterisk that can do transfers between extensions.  If you built
it, get phones to register with it, and connected the outside with
a SIP provider you could do some call traces and see how Asterisk
makes it happen.

A conference is a different animal.  I don't think there is any
SIP call per se to build a conference.  Some UAs have the
function built in, and they actually create more than one phone call
and mix the sound internally.  For example, the Cisco 7960 IP
phone does that.

  I guess the basic problem is that SIP is a protocol, transfer is
a feature that is implemented with the SIP protocol. There are
quite a few ways to skin that cat :-)

-g


On Nov 4, 2004, at 4:46 PM, Bob Carlson wrote:

> I sent this earlier and got no responses.  Perhaps this is not the 
> right
> forum to ask this question.  Can any one suggest a better place to go 
> for
> this information?
>
> Thanks, Bob
>
> -----Original Message-----
> From: Bob Carlson
> Sent: Wednesday, November 03, 2004 3:22 PM
> To: 'SerUsers'
> Subject: Transfer and Conferencing
>
> Let me apologize in advance for my question, which is a little 
> rudimentary.
> We are just starting a project that will use SER and I am being forced 
> to
> document right now how transfer and conferencing will be handled.  I 
> have
> spent a lot of time looking for definitive information on the subject 
> with
> no luck.  Well, maybe too much luck.  There seem to be many proposals 
> and
> models and so on, but it is not clear to me what is actually being 
> done in
> practice.  I have downloaded all the RFCs and proposal papers on the
> subject.  I am still reviewing them, but I think the folks on this 
> forum can
> help me a lot.
>
> I need to know the SIP message sequences for performing a call 
> transfer and
> a blind call transfer and for constructing a conference.  I have found
> information in proposals, but I need to know what actual, available SIP
> phones can do.  We have some phones that we will test, but I do not 
> know
> what they do when you press their transfer and conference buttons.  
> Pardon
> me again for my impatience in asking before I have tried this out.
>
> The Transfer models are straightforward, but conferencing is more
> complicated.  We must construct a simple conferencing model where the
> conferencing is performed by a central server, a SIP IPX.  Only 
> conferences
> of 3 participants need to be supported.  We want it to look exactly 
> like
> 3-way calling on your home phone.  During a call, put the call on hold 
> with
> a conference button, call another phone, hit conference button, the two
> calls are joined in a 3-way conference.
>
> The document draft-ietf-sipping-service-examples-07.txt seems to be 
> very
> helpful on the subject, but all examples are in the form of 3 or more 
> UAs
> and do not address any examples from the point of view of a PBX.  I 
> can see
> how to extend the examples to a PBX case, except for one aspect.  If 
> the
> IP-PBX is to perform the action as a proxy, what does the phone send 
> the
> IP-PBX to indicate the steps in the process.  Put more plainly, what 
> happens
> when the user hits the Transfer or Conference button on the phone?  
> What
> message is sent to the IP-PBX?
>
> Can anyone tell me where else I should be looking?  Is the service 
> examples
> draft the best base document to work from?
>
> Thanks in advance, Bob Carlson
>
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>
>
Greg Fausak
www.AddaBrand.com
(US) 469-546-1265