Signaling System 7 (SS7) is a telecommunications signaling protocol employed within public switched telephone networks (PSTN). Its primary function is to facilitate the setup, management, and teardown of telephone calls, especially when calls traverse multiple networks between origin and destination. SS7 transmits signaling data in the form of digital packets, ensuring efficient and reliable communication.
How SS7 Works:
SS7 utilizes out-of-band signaling, meaning that signaling data is transmitted over a dedicated channel separate from the voice transmission path within the PSTN. For instance, SS7 can convert a phone signal from a local switch into a data stream, route it across the Internet, and then terminate it at a distant local switch near the call’s recipient. This conversion and routing capability provides significant flexibility and efficiency.
SS7 and International Calling:
SS7 plays a crucial role in enabling Voice over Internet Protocol (VoIP) services, particularly for international calls. By converting standard digital phone signals into data streams suitable for internet transmission, SS7 facilitates seamless international communication. The voice clarity achieved is often comparable to, or even surpasses, that of traditional wired calls.
Additional Capabilities of SS7:
Beyond call management, SS7 supports a wide array of supplementary telephony services, including call forwarding and wireless roaming. It also facilitates caller ID delivery, three-way conference calls, and the use of toll-free numbers. Furthermore, SS7 streamlines the capture of billing information, providing detailed records for subscribers and simplifying billing processes for service providers.
Detecting SS7 Usage:
For most users, it’s virtually impossible to discern whether a call is routed via SS7. While there might be a slight delay during the switching process in some instances, the sound quality remains consistently high, provided a stable internet connection is maintained.