Signaling System No. 7 (SS7) is a signaling network and protocol that is used globally to bring telecommunications networks, both fixed-line and cellular, to life. SS7 has numerous applications and is at the very heart of telecommunications. Setting up phone calls, providing cellular roaming and messaging, and supplying converged voice and data services are only a few of the ways that SS7 is used in the communications network. SS7 also provides the point of interconnection between converging voice and data networks. This transition, which affects everyone who works with the data network, has bolstered the need for practical and applied information on SS7. In short, anyone who is interested in telecommunications should have a solid understanding of SS7.