[SIPForum-discussion] No Ring Back Tone Issue

Wed Sep 3 01:20:33 UTC 2008

Dear VB, Raghul, Cliff, Torstein, Vijay, Shyw13, Raghavendra and All, 

Thanks and appreciate so much in sharing your know how, comments and tips, which all are based on the existing standards and solid experience and background.

One most important thing I need to clarify....

"As per standard, should our 183 response to the callee, SHOULD already have SDP? For them then to play the ring back tone locally? Though we have the SDP on our 180 response, but they can't consider processing it somehow" 

Below is the email explanation of our partner on how their SIP system handles our 183 and 180 responses. And with this, they wanted us to embed SDP in our 183 message. Is their request to us still standard for SIP?

SIP Partner wrote:
 With regarding on mentioned packet data SDP(Session Description Protocol RFC2327) Yes, that should be the important keywords and necessary packet in the sip connection for figure out this case .
We think following matter is the highlighted point which is complicating.
------------------------------------------------------------------------
1)
Our source device can accept the alerting message "only one time". but your destination device didn't have SDP packet data when you advertise us the "FIRST"alerting message.
That is why we couldn't realize the ring tone , even though your destination device prepared the SDP packet data on the second exchange of alerting. 
(Our source device cannot accept second contact for alerting from destination device.)
2)
So ,we 'd like you to figure out the cause of missed SDP data on your first alerting message. 
We believe so that our source device can realize the ring tone sounds, 
if we receive your SDP on your first contact for Alerting message.
------------------------------------------------------------------------
Point)
"Alerting message & SDP which you have prepared are correct", but our source device need you to succeed it on the "the first time" of 
alerting negotiation.

Sorry for my poor explanation , but i hope it can be your good help...

Thank you

I wish that you all say and comment, for it's in the standard, that SDP in 183 SHOULD NOT be the basis for playing the ring back tone for it's the SDP in the 180 that SHOULD be the basis.

Regards,
Mon

----- Original Message ----
From: Torstein Knutsen <torstein.knutsen at gmail.com>
To: "WIGNELL, CLIFFORD (CLIFFORD)" <cwignell at alcatel-lucent.com>
Cc: discussion at sipforum.org
Sent: Friday, August 29, 2008 2:46:59 PM
Subject: Re: [SIPForum-discussion] No Ring Back Tone Issue

Hi there

Beware that most operators do not allow early media as a default configuration. Especially if you have an ISDN interconnect, it's not usual enabled from the operators side. Meaning that "you" cannot send early media back to the operaor.
Meaning that if a call flows trough your net like this : (A-sub->PSTN->SBC1->...internet...->SBC2->PSTN->B-sub) Then early media(ringtones, announcements etc) from B-subs "PSTN" will not reach A-subs PSTN if SBC1's interconnect stops early-media...

regards
Torstein

On Fri, Aug 29, 2008 at 12:39 AM, WIGNELL, CLIFFORD (CLIFFORD) <cwignell at alcatel-lucent.com> wrote:

Hello Raghul,

Look at RFC3666, it describes the SIP<->PSTN call flows, by contrast RFC3665 provides "normal" SIP flows; good places to start.

Best regards

Cliff Wignell

________________________________

From:discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Raghul Prasanna
Sent: Friday, 29 August 2008 5:33 AM
To: Vivek Batra
Cc: discussion at sipforum.org 

Subject: Re: [SIPForum-discussion] No Ring Back Tone Issue

HI Vivek,

 From your explanation I can understand that 183 with SDP result in early media, but incase of 180 with or without SDP with no 183, will reult in UA playing local ringback tone..

Just want to know is there any RFC that says the above point...

Thanks,
Raghul

--- On Wed, 27/8/08, Vivek Batra <vivek7683 at gmail.com> wrote:
From: Vivek Batra <vivek7683 at gmail.com>
Subject: Re: [SIPForum-discussion] No Ring Back Tone Issue
To: "ramon nolasco" <rpnolasco at yahoo.com>
Cc: discussion at sipforum.org
Date: Wednesday, 27 August, 2008, 4:09 PM
Comments inline in RED.

--VB
On Wed, Aug 27, 2008 at 9:23 AM, ramon nolasco <rpnolasco at yahoo.com> wrote:
Hi All,

Greetings and a good day to all of you! I have this and quite a rare one to me of "no ring back tone" problem with one of our interconnecting partners. Partner claims that our system normally sends "183 Session Progress" and "180 Ringing". That we are sending "183 Session Progress" without the ringtone data though our "180 Ringing" has a ringtone data. That their system looks for the ringtone data to process from the first received message response, which is our "183 Session Progress" and afterward disregards our "180 Ringing" response that followed, wherein the ringtone data is indeed present,  thus resulting to a successfull call but without ringback tone. 

My questions are, per standard:
	1. When and why does "183 Session Progress" is being sent as a response?
 '183 Session Progress' or referred as Early Media is generally sent when media (RTP) is required within early dialog. 
Media is required in the early dialog when the call is placed from IP to PSTN. 
When ITSP/ Gateway routes the call from IP to PSTN, it generally sends the 183 response with SDP body and all the tones/ message are played by gateway to UA. However in case of 180 Ringing, RBT is played by local UA itself.
	1.  
	2. Should "183 Session Progress" sometimes also can replace "180 Ringing", thus have the ringtone data? or
Yes. It depends on the local policy of UA whether it wants to stop the media created with 183 Session Progress and start playing local RBT or discards the 180 Ringing (recieved after 183 Session Progress) and remains connect the media till the final response. 
You will found lot of UA in the marked having both type of implementations. 

	1.  
	2. or it's always "180 Ringing" that has the ringtone data?
I am not sure what you are referring as Ringtone data. I believe that you are referring whether 180 Ringing has SDP or not.
If you are referring the same, my answer would be Yes. 180 Ringing can have SDP body but this is not used to connect early media. 180 Ringing with SDP refers the Offer-Answer model as per RFC 3262.
Only 183 Session Progress is sent as response to connect early media.
	1.  
	2. Our setup is SBC-to-SBC, Huawei Eudemon 2300-to-Mediaring Voizbridge, is it us who really has the problem or who needs then to adjust? Adjust what?
In the above statements, you are referring that 183 Session Progress has no ringtone data. What actually you are referrig? You want to say that 183 Session Progress has no SDP? 
Can you provide us the complete call flow?
	1.  
	2. Is my partner's claim of "the should be system flow and process" standard?
Appreciate any of your solution advice and many thanks in advance :)

Best regards,

Mon

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