[SIPForum-discussion] No Ring Back Tone Issue

[WIGNELL, CLIFFORD (CLIFFORD)]

Hi All,

 

Just a comment on 183 vs 180,

 

The reason early media is used when interconnecting with the PSTN/PLMN
is that the backwards audio path can carry more information than just
ringing, many times a call will be processed by a "Treatment" such as
playing an announcement such as "The number you have dialed is not
connected......". It is not normally the Gateway that plays these (MG)
although it is possible to play announcements and tones form the MG, it
is usually the Terminating PSTN Switch, but any Switch in the chain
could potentially Treat the call. It's important to note that not all
call Treatments end the call, there are such treatments as number
interceptions where the announcement will be something like "The number
you have dialed has been changed, the new number is......" and then the
call is forwarded to the new number.

 

Thus, in the case of a PSTN/PLMN you can't just play ringing from the
UE, information may be lost.

 

Best regards

 

Cliff Wignell

________________________________

From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Vivek Batra
Sent: Thursday, 28 August 2008 1:09 AM
To: ramon nolasco
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] No Ring Back Tone Issue

 

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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