[asterisk-dev] 13.24.1 / PJSIP: early media via 180 Ringing containing SDP is ignored

[Joshua C. Colp]

On Fri, Jan 25, 2019, at 6:11 AM, Michael Maier wrote:
> On 24.01.19 at 12:08 Joshua C. Colp wrote:
> > On Thu, Jan 24, 2019, at 7:00 AM, Michael Maier wrote:
> >> Hello!
> >>
> >> Given is an outbound call to a callee via asterisk to the ISP. After 
> >> INVITE, the ISP sends 100 Trying and some time later 180 Ringing *w/* 
> >> SDP and the header
> >> "P-Early-Media: sendonly" (no 183 or any other thing until callee 
> >> responds). SDP in 180 contains media attribute *sendrecv* 
> >> (contradicting to the P-Early-Media header).
> >>
> >> Asterisk 13.24.1 sends PRACK to the ISP (w/o SDP) and the 180 to the 
> >> caller - but SDP is dropped and therefor no early media is possible!
> >>
> >> Is this behavior a bug or a feature?
> > 
> > It would be a bug. That's not a scenario that I think anyone has really tested or fully scoped out. Is media actually received while in the 180 with Ringing stage?
> > 
> 
> Just a quick thought:
> Would it be a valid workaround to enable inband_progress for the 
> calling extension? This ensures, that a media session is always 
> generated - especially for an incoming 180.
> The question now is: if the ISP sends media and asterisk creates media 
> itself (as it told) - which media is preferred? Will asterisk drop 
> ISP's media in favor of its own
> media? Or will it pass the ISP's media and drop own media?

I haven't touched this scenario so I don't know the ripples that may occur... but I believe Asterisk generated on the egress would overrule media received on the ingress.

-- 
Joshua C. Colp
Digium - A Sangoma Company | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
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