SIP - Introduction

Signaling System No. 7 (SS7) is a set of telephony signaling protocols developed in 1975, which is used to set up and tear down most of the world's public switched telephone network (PSTN) telephone calls.

Mobicents is an Open Source VoIP Platform written in Java to help create, deploy, manage services and applications integrating voice, video and data across a range of IP and legacy communications networks

https://github.com/RestComm/sipunit   - sip unit test