Subject: [Sipping] SIP method for sending telephony signals

From: "Mohana Sundaram" <[email-masked]>
Date: Thu, 3 May 2007 21:42:12 +0530

Hi All,

Is there any standard for sending telephony signals(like onhook/offhook )
and telephony tones through SIP.

A quick look at kpml standard RFC4730 seems to me like it is only for
sending DTMF digits.

Thanks,
Mohan.

-- 
The expert at anything was once a beginner.
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---

From: "Gaurav Kheterpal" <[email-masked]>
Date: Fri, 4 May 2007 12:33:07 +0530

Refer to RFC 2833 - Section 3.12 & 3.14.

RFC 2833 allows sending DTMF Digits, Telephony tones & signals as RTP
payload in a SIP call.

My 2 cents,
Gaurav

  _____  

From: Mohana Sundaram [mailto:[email-masked]] 
Sent: Thursday, May 03, 2007 9:42 PM
To: [email-masked]
Subject: [Sipping] SIP method for sending telephony signals

Hi All,

Thanks,
Mohan.

---

From: Gunnar Hellström <[email-masked]>
Date: Fri, 4 May 2007 13:01:05 +0200

RFC 2833 is now replaced by RFC 4733 and RFC 4734.

Together they will take care of all telephone tones you want to transfer.

But they do not handle the on hook – off hook events. I think that might be
defined in some event package, but I have not found it.

Gunnar

  _____  

From: Gaurav Kheterpal [mailto:[email-masked]] 
Sent: Friday, May 04, 2007 9:03 AM
To: 'Mohana Sundaram'; [email-masked]
Subject: RE: [Sipping] SIP method for sending telephony signals

Refer to RFC 2833 – Section 3.12 & 3.14.

My 2 cents,
Gaurav

  _____  

Hi All,

Thanks,
Mohan.

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Detta meddelande dr genomsvkt av NOD32 Antivirus.
http://www.nod32.com

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From: "Bischoff, Brent \(Brent\)** CTR **" <[email-masked]>
Date: Thu, 3 May 2007 11:22:36 -0500

Mohan,
 
Take a look at RFC 4733 and see if that meets your requirements.
 
Regards,
Brent

________________________________

From: Mohana Sundaram [mailto:[email-masked]] 
Sent: Thursday, May 03, 2007 12:12 PM
To: [email-masked]
Subject: [Sipping] SIP method for sending telephony signals

Hi All,

Is there any standard for sending telephony signals(like onhook/offhook
) and telephony tones through SIP.

Thanks,
Mohan.

---

From: "Steve Langstaff" <[email-masked]>
Date: Fri, 4 May 2007 04:30:36 -0700

*Assuming* that you are using SIP to place calls using the INVITE method, you (Mohana) might want to consider how your user interface is going to distinguish an on-hook that is meant to CANCEL/BYE an INVITE, from an on-hook that is not. 

	From: Gunnar Hellström [mailto:[email-masked]] 
	Sent: 04 May 2007 12:01
	To: 'Gaurav Kheterpal'; 'Mohana Sundaram'; [email-masked]
	Subject: RE: [Sipping] SIP method for sending telephony signals

	But they do not handle the on hook - off hook events. I think that might be defined in some event package, but I have not found it.

	Gunnar

	RFC 2833 allows sending DTMF Digits, Telephony tones & signals as RTP payload in a SIP call.

	My 2 cents,
	Gaurav

	

	Hi All,
	
	Is there any standard for sending telephony signals(like onhook/offhook ) and telephony tones through SIP.
	
	A quick look at kpml standard RFC4730 seems to me like it is only for sending DTMF digits.
	
	Thanks,
	Mohan.

---

From: Dean Willis <[email-masked]>
Date: Mon, 7 May 2007 14:47:56 -0500

On May 3, 2007, at 11:12 AM, Mohana Sundaram wrote:

> Hi All,
>
> Is there any standard for sending telephony signals(like onhook/ 
> offhook ) and telephony tones through SIP.
>

Nope. It does suggest mapping flash to R.

But in my experience, if you think you need to send "flash" over SIP,  
then you probably shouldn't be using SIP. You should be using MGCP or  
some other stimulus-response protocol.

The hook operation should change state in the local user interface,  
not communicate a state change to a remote softswitch.

Why do people keep trying to slavishly replicate PSTN behavior using  
SIP? Can't they just use the PSTN if that's what they want?

--
Dean

---

From: "VAN TILBURG Rudi" <[email-masked]>
Date: Tue, 8 May 2007 13:58:25 +0200

IMHO,

Keep in mind that the all the standards are currently moving to a
SIP-centric call control core. So one way or the other. And depending on
where you want to position your Application Server functionality you
maybe have to transport a line signal in SIP.

Indeed kpml maps the flash-hook in an active call on the R. The
intention is that the call control Layer requests via KPML a reporting
of the "HookFlash or recall event" (during a session) at the POTS phone
connected to the GW. 
In principle the Keypress markup language should cover all the possible
"key-events" that can be expected from a POTS phone. Since the Recall
button is a known button on a POTS phne also the line-event (Hookflash)
is included. 

RFC4733 (obsoletes RFC2833) it's purpose is to pass in a "compressed
way" the Telephone/event signals via the RTP channel to the peer side,
It is NOT defining the reporting of the telephone/events to the call
control layer. At session setup the peer GWs are informed about the
RFC4733 capabilities via SDP offer/answer.

Some SIP implementors choose for using the SIP-INFO method to report
"Line-Signals" in a proprietary way. The KPML standard is the first
standard that materializes the reporting of the line-signal
(Hookflash/Recall event).

Kind Regards,
Rudi

-----Original Message-----
From: Dean Willis [mailto:[email-masked]] 
Sent: maandag 7 mei 2007 21:48
To: Mohana Sundaram
Cc: [email-masked]
Subject: Re: [Sipping] SIP method for sending telephony signals

--
Dean

---

From: Eric Burger <[email-masked]>
Date: Mon, 14 May 2007 12:55:46 -0400

You have seen a few postings about the availability of RFC 4733, the R
symbol in KPML, and the use of command/control protocols like H.248.

I am curious, what is the use case driving you to ask?  From the use case,
you should be able to determine the approach best for you.

One thing that deserves clarification is that R is the register recall
*KEY*.  It is a button found on many European phones.  KPML does say, " the
device MAY report a hook flash as an R character" because many PBXen do that
today.  However, what RFC 4730 reports is not "the user did a hook flash,"
but "the user emulated pressing the R key [by doing a hook flash]."

What user signaling are you looking for that is not covered by the user
signaling apparatus available to the user, a.k.a. the telephone key pad?
Remember that off-hook is not user signaling; on-hook is user signaling,
a.k.a. BYE or CANCEL; and hook-flash is in never-never land, but covered by
Register Recall.

> SIP? Can't they just use the PSTN if that's what they want?

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From: "Steve Langstaff" <[email-masked]>
Date: Tue, 15 May 2007 02:01:49 -0700

> From: Eric Burger [mailto:[email-masked]] 
> Sent: 14 May 2007 17:56
> To: Mohana Sundaram
> Cc: [email-masked]

> I am curious, what is the use case driving you to ask?  From the use
case, you should be able to determine the approach best for you.

> Remember that off-hook is not user signaling; on-hook is user 
> signaling, a.k.a. BYE or CANCEL

Except that:
  off-hook *can* lead to user signaling when doing some of the BLA
stuff,
And
  on-hook does not lead to user signaling if there was no INVITE to BYE
or CANCEL (e.g. I go off-hook, and then change my mind).

But yes, knowledge of the use case would help in determining whether the
original poster should even be looking for a method of signalling
on/off-hook or not.

---

From: Eric Burger <[email-masked]>
Date: Tue, 15 May 2007 09:25:43 -0400

Why would you want to know when someone picks up a hand set and drops it
off?  If you are trying to replicate the flash-flash-flash means place an
emergency call, I would offer the phone does that itself, or you really want
H.248.