Subject: [SIP] DTMF/voice forking using Join.

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Fri, 13 Apr 2001 05:45:00 -0700

While I'm on a roll ....

Have people thought about using the soon-to-be-proposed Join to replace the
current DTMF/voice forking model (which still has a number of problems in my
mind). 

For example, UA A calls UA B through proxy/B2BUA C. The application server
at C needs to receive a copy of any DTMF/voice sent from UA A (in addition
to the DTMF/voice being sent from A directly to B). An example would be UA A
pressing "#" three times to return to a calling card server application. C
would simply send a Join to UA A such that UA A sends a copy of voice to C.
This would also allow C to easily play messages to A (eg "You have 1 minute
remaining."). 

To work properly, this would require that the Join mechanism allows the
Joiner to specify whether full or only local-mixing is to be performed by
the joinee. In other words, whether the joinee mixes media only to/from the
local terminal (with the joiner), or whether the joinee mixes media between
all parties (conference bridge style). 

Could not Join also be used to easily meet regulatory eavesdropping
requirements? 

Where is status of Join at the moment?

Regards,

Robert.

---

From: "Rosen, Brian" <[email-masked]>
Date: Mon, 16 Apr 2001 09:17:12 -0400

>Could not Join also be used to easily meet regulatory eavesdropping
requirements? 
I doubt it.  One of the more interesting aspects of legal intercept is that
neither party, NOR ANY NORMAL TEST TECH, WITH NORMAL TEST EQUIPMENT, can
detect the presence of a tap.  That means that, unless completely encrypted,
with no observable difference in message length, you can't have any
signalling difference anywhere between a tapped and an untapped call.
It probably means that no signalling mechanism can be helpfull in any
way to legal intercept. It's always possible to employ a whole lot of
mechanism to get around this issue, but I suspect it won't be worth it,
as there are more straightforward ways to achieve the goals.

Brian

_______________________________________________
This list is for continuing development of the SIP protocol.
The sip-implementor's list is the place to discuss implementation,
and to receive advice on understanding existing sip.
To subscribe to it, send mail to 
[email-masked] with "subscribe" in the body.

---

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Mon, 16 Apr 2001 06:27:32 -0700

HI Brian,

That does not preclude this being performed on a SIP-PSTN gateway where the
PSTN subscriber (and the remote SIP subscriber) will be unable to detect the
tap. However, I take you point Brian. Does anyone know if there are any
current legal requirements to tap pure IP-only calls? If not, its probably
only a matter of time before some silly country requires this.

Robert.

-----Original Message-----
From:	Rosen, Brian [mailto:[email-masked]]
Sent:	Monday, April 16, 2001 2:17 PM
To:	'Fairlie-Cuninghame, Robert'; [email-masked]'
Subject:	RE: [SIP] DTMF/voice forking using Join.

requirements? 

Brian

---

From: "Rosen, Brian" <[email-masked]>
Date: Mon, 16 Apr 2001 09:53:37 -0400

Sure, but you can't depend on all calls going through such a gateway.
 
I believe there are places that can tap an IP stream.  I think it's just a
matter of time
before that will be legal everywhere.  I also think we will have increased
use of
encryption, which will make it hard (for most LEAs, probably impossible) to
tap.
The observation that we probably WILL have to deal with IP taps leads me to
believe that the tap point is probably the access router.  That idea gives a
lot
of people the willies, but it's the most practical answer.  Among other
things,
if a residential gateway calls another residential gateway, the only place
you 
COULD tap would be the access router.  Better not, for example, see any
IP address difference, any signalling difference, or any management stream
difference in the gateway (which is on the suspect's premises, and thus
assumed to be compromised). 
 
Having said that, I remind everyone that the IETF will not support protocol
mechanisms 
whose only purpose is legal intercept, of any kind. 
 
Brian

-----Original Message-----
From: Fairlie-Cuninghame, Robert [mailto:[email-masked]]
Sent: Monday, April 16, 2001 9:28 AM
To: 'Rosen, Brian'; [email-masked]'
Subject: RE: [SIP] DTMF/voice forking using Join.

HI Brian, 

Robert. 

BM__MailData-----Original Message----- 
From:   Rosen, Brian [ mailto:[email-masked]
<mailto:[email-masked]> ] 
Sent:   Monday, April 16, 2001 2:17 PM 
To:     'Fairlie-Cuninghame, Robert'; [email-masked]' 
Subject:        RE: [SIP] DTMF/voice forking using Join. 

requirements? 

Brian

---

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Mon, 16 Apr 2001 06:58:10 -0700

Agreed. This was only an afterthought I had for the usage of Join and not
the main thrust of my email (hence the title of the email). 
 
Regards,
 
Robert.

-----Original Message-----
From: Rosen, Brian [mailto:[email-masked]]
Sent: Monday, April 16, 2001 2:54 PM
To: 'Fairlie-Cuninghame, Robert'; [email-masked]'
Subject: RE: [SIP] DTMF/voice forking using Join.

 
 
Brian

-----Original Message-----
From: Fairlie-Cuninghame, Robert [mailto:[email-masked]]
Sent: Monday, April 16, 2001 9:28 AM
To: 'Rosen, Brian'; [email-masked]'
Subject: RE: [SIP] DTMF/voice forking using Join.

HI Brian, 

Robert. 

requirements? 

Brian