asterisk users - Dec 2018 - Outbound call: caller gets no ringback on session progress

On 12.12.18 at 19:43 Joshua C. Colp wrote:
> On Wed, Dec 12, 2018, at 12:31 PM, Michael Maier wrote:
> 
> <snip>
> 
>>
>> The problem: The extension doesn't create a ringback locally,
because
>> it most probably expects it to
>> be sent by the callee - but the callee doesn't send anything (not 
>> surprising, because there has been
>> no SDP).
>>
>> Or should Asterisk create the ringback (Asterisk doesn't send any
RTP
>> package)? Or should the phone
>> create the ringback itself because there is a 180 Ringing (even if it 
>> contains SDP)?
>>
>> I'm wondering: Why does Asterisk create a 183 to the extension 
>> containing SDP if the callee didn't
>> provide any SDP?
>>
>>
>> So many questions ... . Could somebody please shine some light on it? 
>> What's going wrong here?
> 
> The core doesn't communicate whether progress includes media or not, so
the PJSIP channel driver (and even chan_sip) assumes media is there.
Another question: is there any use case for 183 Session Progress w/o SDP? IOW:
Is a 183 Session
Progress just a bug of the ISP? If so, problem could be solved by dropping each
183 package w/o SDP.


Thanks,
Michael

On Sun, Dec 16, 2018, at 4:43 AM, Michael Maier wrote:

<snip>
> 
> Another question: is there any use case for 183 Session Progress w/o 
> SDP? IOW: Is a 183 Session
> Progress just a bug of the ISP? If so, problem could be solved by 
> dropping each 183 package w/o SDP.
Nothing really comes to mind that would be accomplished by sending a 183 without
SDP but there may be cases on the internet.

-- 
Joshua C. Colp
Digium - A Sangoma Company | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org

On 17.12.18 at 11:52 Joshua C. Colp wrote:
> On Sun, Dec 16, 2018, at 4:43 AM, Michael Maier wrote:
> 
> <snip>
> 
>>
>> Another question: is there any use case for 183 Session Progress w/o 
>> SDP? IOW: Is a 183 Session
>> Progress just a bug of the ISP? If so, problem could be solved by 
>> dropping each 183 package w/o SDP.
> 
> Nothing really comes to mind that would be accomplished by sending a 183
without SDP but there may be cases on the internet.
> 
As long as [1] aren't fixed, the attached patch could be used as workaround.
This workaround drops 183 Session Progress w/o SDP.

The attached workaround assumes, that 183 Session Progress w/o SDP is followed
by 180 Ringing. If there isn't any 180 Ringing following, this patch
won't fix anything. In
the latter case, it would be necessary to generate inband ringing by asterisk or
send 180 Ringing instead of the broken 183 Session Progress.

The workaround applies to 13.24.1.



Caller		Asterisk				ISP
-----------------------------------------------------------------------------
Invite -------->
...
			<-----------------------	183 Session Progress w/o SDP
			<-----------------------	180 Ringing
<---------------180 Ringing
...



Another 183 Situation with *P-Early-Media* header
================================================
Caller		Asterisk			ISP
-----------------------------------------------------------------------------
Invite -------->
...
		    <--------------------------		183 Session Progress w SDP /
P-Early-Media:sendonly
<-------------	183 Session Progress w SDP sendrecv
<-------------  RTP
--------------> RTP
		    <--------------------------		180 Session Progress w/o SDP /
P-Early-Media:sendonly
		    <--------------------------		RTP (inband ringback)
...

=> the sendonly-value of P-Early-Media seems to be ignored. Asterisk
doesn't apply the sendonly value of the P-Early-Media header of the 183
Session Progress package
received from the ISP to the 183 Session Progress sent to the caller.
But this is not a problem, as the ringback can still be transferred.


Regards,
Michael


[1] https://issues.asterisk.org/jira/browse/ASTERISK-28208,
https://issues.asterisk.org/jira/browse/ASTERISK-27994
-------------- next part --------------
A non-text attachment was scrubbed...
Name: res_pjsip_session.c.diff
Type: text/x-patch
Size: 934 bytes
Desc: not available
URL:
<http://lists.digium.com/pipermail/asterisk-users/attachments/20190122/4ef72bf6/attachment.bin>