SIP High Level Architecture

../_images/hla.png

As most of VoIP systems do, dialog decouples signaling (such as call state messages, invite / answer information, etc) and media traffic (audio/video streams). We use SIP signaling for external integrations, OPUS/PCMA/PCMU for audio and VP8 for video.

If you want your clients to be able to call from different networks (basically in every case if you want to call from internet), you will also need to setup an ICE server (TURN).

SIP Signaling

Dialog SIP extension works as a back to back user agent (B2BUA), i.e. it registers on a SIP server on behalf of the end user, translates and forwards SIP commands to the dialog clients.

Dialog SIP extension supports SIP over following transports: TCP, UDP, SCTP, TLS, WS (websocket), WSS (secure websockets).

If you’re using TLS or WSS you will also need to setup a correct SSL certificate on your SIP server.

Your SIP Registrar server should be is accessible from the Dialog Serer.

Media traffic

Dialog SIP extension does not perform any media transcodings and expects SIP clients to understand clients media (which is WebRTC).

In case if you’re using ICE servers, you should make them accessible for external SIP clients (or from SIP PBX if it is in relay mode).

Security

Media traffic between dialog clients and SIP clients secured by DTLS (in fact, WebRTC enforces usage of DTLS for all media connections).

Warning

Signaling traffic between dialog SIP Extension and SIP Registrar is secured only if you’re using TLS / WSS.

You may consider possibility of using unsecure protocols, such as TCP/UDP/WS if both SIP Registrar and dialog server are in private network secured by firewall.