[SIPForum-discussion] FAKE RBT Scenarios

[ashish rawat]

Hello Shah,

I suggest you take packet capture and see when do you get the actual ring-back from the far end. If you see RTP packets right after 180 then probably it might be delay by your client to cut through the audio.

Moreover you can also have a look at "o" field in the sdp. If the version number in the "o" field in the sdp of 180 and 183 are same , then an endpoint might also choose to ignore the sdp in 183.


o=<username>
<sess-id> <sess-version> <nettype> <addrtype>
       
<unicast-address>
 
<sess-version>
is a version number for this session description.  Its
     
usage is up to the creating tool, so long as <sess-version> is
     
increased when a modification is made to the session data.  Again,
     
it is RECOMMENDED that an NTP format timestamp is used
 
https://www.ietf.org/rfc/rfc3264.txt
 
  
Nearly all aspects of the session can be modified.  New streams can
  
be added, existing streams can be deleted, and parameters of existing
  
streams can change.  When
issuing an offer that modifies the session,
   the "o=" line of
the new SDP MUST be identical to that in the
   previous SDP, except that
the version in the origin field MUST
   increment by one from the
previous SDP. 
If the version in the origin
  
line does not increment, the SDP MUST be identical to the SDP with
  
that version number
Thanks,
Ashish Rawat




On Friday, 31 January 2014 12:59 AM, Stephen James <sjames_1958 at yahoo.com> wrote:
 
This is pretty normal for early media such as custom ringback or announcement from the far end. 
Since the 183 doesn't have 100rel/PRACK then sending SDP twice is ok. If the 183 is sent reliably there shouldn't be SDP is later responses.


 
Stephen James 
sjames_1958 at yahoo.com
 
We are not princes of the earth, we are the descendants of worms, and any nobility must be earned.



________________________________
 From: Shah Hussain Khattak <shahhusayn at msn.com>
To: "discussion at sipforum.org" <discussion at sipforum.org> 
Sent: Tuesday, January 28, 2014 12:19 PM
Subject: [SIPForum-discussion] FAKE RBT Scenarios
 


 
Hello All SIP Experts, 

Can you guys please confirm me is below scenario normal:

Call Invite ---------------->

183 session in progress without SDP <----------------------------
183 session in progress with SDP      <----------------------------

then

180 ringing with SDP <---------------------------------------------

i just want to know is above call flow normal? 

2nd thing, is 180 ringing with SDP creating fake RBT for calling party side? 


Regards, 
Shah Hussain 







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