Aaron, thank you. Was a little bit tricky to install it as our slapd isnt in the right version.. But it seems to work now.. Error messages no longer appear. Now the message is quiet better: 9(9381) INFO: rtpengine [rtpengine.c:1627]: rtpp_test(): rtp proxy <udp:127.0.0.1:22222> found, support for it enabled Again, thank you! ? ________________________________ Von: sr-users &lt;sr-users-bounces(a)lists.sip-router.org&gt; im Auftrag von Aaron Hamstra &lt;ahamstra(a)carnegietechnologies.com&gt; Gesendet: Donnerstag, 28. Januar 2016 21:14 An: Kamailio (SER) - Users Mailing List Betreff: Re: [SR-Users] P-CSCF Fred, I think you would need to use rtpengine instead of rtpproxy. https://github.com/sipwise/rtpengine -Aaron From: sr-users [mailto:sr-users-bounces@lists.sip-router.org] On Behalf Of Fred Schulz Sent: Thursday, January 28, 2016 1:24 PM To: sr-users(a)lists.sip-router.org Subject: [SR-Users] P-CSCF Hi all, we're just playing around with an IMS setup bases on kamailio. Therefore the kamailio is used as P-,I- and S-CSCF. We where able to register two clients through all components. As we wan to start a call session, the P-CSCF answers with "403 - Forbidden. You must register with an S-CSCF"... I found this snippet in kamailio.cfg: if (!pcscf_is_registered("location")) { send_reply("403","Forbidden - You must register first with a S-CSCF"); break; } Can one tell me what exactly the kamailio is checking there? As I figured out it is looking in database location table. The table contains the registered users registered towards the IMS. Another "problem" we faced with is the rtpproxy. As the ngcp-mediaproxy-ng is no longer available and replaced with rtpproxy we're trying to use it. But kamailio said that the proxy isn't answering the way expected. ERROR: rtpengine [rtpengine.c:1622]: rtpp_test(): proxy responded with invalid response Any advise would be nice. Thank you Fred