outbound ring tone
NoelB:
Quote from: ianobi on August 06, 2015, 09:27:24 am
@ drgeoff
Attached is a Wireshark trace of a call I have just made from my OBi1032 using sipgate to my mobile. I did not answer the call. Times show:
1643:17 - RTP established in both directions (early media).
I now hear ring back tone.
I can only comment from an Au viewpoint ( and just forget the cricket :(
Most of what you describe is the same here but the only time we see a 180 ringing is when a local sip client sends it in response to an incoming call to alert the sip proxy that the invite has been received. All the vsps here use a 183 Session Progress to initiate early media and only on a rare occasion have I seen an incoming 180 ringing --never both. A 180 will have been generated by the remote UA but not passed on by the sip proxy if a 183 has been sent. The 183 is generated at the sip/PSTN gateway and sent via the sip proxy server to the sip client and 2 way early media commences. This is also important as it gives the sip media server a chance to adjust the rtp destination port if it has been fooled by the clients napt
In your wireshark ladder map I cant understand how you can hear ring back tone unless our definition is different to yours . With the 183 and early media we would hear the actual pstn ring tone or engaged tone not a generated ring back tone.
ianobi:
@ NoelB
Quote
I cant understand how you can hear ring back tone unless our definition is different to yours . With the 183 and early media we would hear the actual pstn ring tone or engaged tone not a generated ring back tone.
I agree. That's exactly what I meant. The early media allows the tones from POTS / PSTN / cellular to be routed back through the sip proxy to sip client to caller. I have modified my post to make that more clear.
Your good description of how early media works using 183 Session Progress by itsps / vsps is the most usual way of doing things. However, if you follow the link provided by drgeoff above you will see that the rfc standard does describe how user clients (such as OBi devices) should react to receiving 180 ringing messages. I think we are pretty much in agreement here!
I promise not to mention the cricket more than once a day for the next few weeks :D
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