From MyVoipApp Information System:
mini SIP Server (20 clients) is based on the SIP standard which is an open standard. There are so many SIP phones (software or hardware), you can choose anyone you like without vendor lock in. It is very easy to setup and manage your own VOIP system. In fact, you can use MSS to deploy a basic VOIP network in 1 hour. mini SIP Server (20 clients) features GUI configuration, web management, call detail record, and instant message. In 20 clients edition CPS (call per second) is 3.