Subject: [AVT] line tones usage in RTP traffic

From: "Murat Artun" <[email-masked]>
Date: Tue, 10 Oct 2006 17:00:29 +0300

Hello,

I have searched AVT for the line tone usage. I have found this post of
Tom-PT Taylor which was posted one year ago:

http://www1.ietf.org/mail-archive/web/avt/current/msg05937.html

In this post, it was stated that line events other than DTMF events
are only needed "for interworking with legacy lines". In addition, it
was stated that "there was no evidence they were actually implemented
by anyone".

I want to ask what the possible scenarios could be "for interworking
with legacy lines".

In addition, I want to learn if there was evidence that line events
defined in RFC2833 were implemented by someone in the past one year.

Another point is that it seems as if line events will be out of use
with the RFC2833 by a new draft. Because, I found that codes for line
events are marked to be deprecated on page 55 of
draft-ietf-avt-rfc2833bis-15.txt. However, this draft gives more
details about "RTP Payload Format for Telephony Tones" compared to
current RFC2833. This draft also gives details about the SDP
specification about "RTP Payload Format for Telephony Tones" which was
missing in RF2833. Does this mean that with the update to RFC2833 line
tones will be used only as "RTP Payload Format for Telephony Tones"?
Or, this payload type definition is also kept only for interworking
with legacy lines, and no implementation is currently found?

In addition, considering that SIP is used as a signaling protocol,
what could be a scenario for the need for interworking with legacy
lines?

Thanks ...

-- 
M u r at  A r t u n, MSc.
   Software Engineer

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

---

From: "Tom-PT Taylor" <[email-masked]>
Date: Tue, 10 Oct 2006 14:16:48 -0400

Hi. See below marked with [PTT].

> I want to ask what the possible scenarios could be "for interworking
[PTT]Imagine an architecture like this. I don't know of any implementation.

   __                ____                   ____
  |  |               |  |                   |  |
   --  --------------|  |-------------------|  |
Analogue            ----    IP connection  ----
Telephone         RFC 2833                 Call
                   gateway                  Server

The signals to and from the analogue telephone are converted at the RFC 
2833 gateway along with the voice or other content of the ensuing 
conversation. The IP connection carries RFC 2833 line events as well as 
packetized voice.

I suspect this architecture may have been in someone's mind when RFC 
2833 was defined, but got overtaken by the popularity of MGCP and 
Megaco/H.248. As a result, no implementations (that I know of) reached 
the market. Certainly no one responded when we asked during the process 
of creating the update to RFC 2833. Within the past few months, however, 
Aleksandar Lebl ([email-masked], note) expressed an interest in having 
such events defined. If you have an use for them, perhaps you could work 
with Aleksandar on a new Internet Draft for the purpose.

---

From: [email-masked]
Date: Wed, 11 Oct 2006 16:43:59 +0200

Tom,
I know such (early) "NGN" implementations, but without RFC2833 mode, i.e.
line tones were carried within the RTP voice packet (pass-through mode).
- Albrecht

                      "Tom-PT Taylor"                                                                                                 
                      <[email-masked]         To:      Murat Artun <[email-masked]>                                            
                      om>                      cc:      [email-masked]                                                                  
                                               Subject: Re: [AVT] line tones usage in RTP traffic                                     
                      10.10.2006 20:16                                                                                                

   __                ____                   ____
  |  |               |  |                   |  |