SIP Softphone(s)

Many telephone systems (PBXs) make the operation of telephones possible that have been implemented according to the SIP standard. estos UCServer supports the central integration of such telephone systems. This integration allows estos ProCall client users to use their PCs as softphones in order to make telephone calls through the telephone system. To do this, the ProCall client gets one or more lines, that respectively correspond to one telephone from UCServer.

To configure UCServer, one such line that is respectively responsible for registration of a certain telephone number must first be added. Afterwards, the line will be assigned to a user with the help of this telephone number. Thereby, the ProCall client users can use the telephone system for making telephone calls through UCServer.

UCServer already has the SIP modules necessary for PBX integration, which assume control of the call signals. In addition, UCServer contains a media server that binds the PBX on the one hand and the ProCall clients on the other hand with each other. By using the media server, the media streams will respectively be converted into the correct format. On the client side, the media streams are encrypted (DTLS-SRTP), even when the PBX does not provide encryption. The telephonic accessibility of the users located on the Internet is another job of the media server. If a ProCall Mobile client is outside of the reach of the internal WLAN or, for example, a PC client is in a home office, the central PBX can continue to be used for making telephone calls.

Technical Information

The telephone system must allow registrations through a LAN interface in accordance with the SIP standard (RFC 3261). UCServer does not need a SIP-specific license. However, some telephone systems need licenses in order to register SIP softphones with the telephone system.

Connection to telephone systems via SIP trunk or via classic SIP registration
Softphone lines can be connected to the telephone system via a classic SIP registration or via a SIP trunk. The classic SIP registration registers one line per registration with the telephone system. With a SIP trunk, multiple lines are controlled by a signaling connection. A SIP trunk can be addressed by a fixed IP address, whereby all predefined lines are immediately available without registration. However, depending on the telephone system, a SIP trunk can also put a bundle of lines into operation through a single register. In this case, the UCServer registers with the SIP trunk of the telephone system.

Media Server
The media server offers the audio codecs G.711 (PCMU, PCMA), G.722 and Opus for the PBX. Opus is mostly used towards ProCall Client. This offers good audio quality even with little LAN/WAN bandwidth. With encryption using the DTLS/SRTP method, the Media Server uses the highest security standard that is currently common in VoIP products.

Accessibility on the Internet
Accessibility on the Internet via the Media Server is achieved by using TURN/STUN Server services. These can be provided by your own infrastructure or by estos UCConnect services. If no TURN/STUN servers are configured, communication within the local LAN is possible.