Signaling System 7 (SS7) is a protocol suite that operates within a public switched telephone network (PSTN). Its primary function is to facilitate the setup, management, and teardown of telephone calls, especially when calls traverse multiple networks. SS7 transmits signaling data in the form of digital packets, enabling efficient communication between network elements.
**How SS7 Works**
SS7 employs a technique called out-of-band signaling. Unlike traditional in-band signaling where control signals share the same channel as voice data, out-of-band signaling uses a dedicated channel for transmitting control information. For example, SS7 can convert a phone signal from a local exchange into a data stream, route it over the internet, and terminate it at a distant local exchange near the call 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). By converting standard digital phone signals into audio streams suitable for internet transmission, SS7 makes international calls seamless. The voice clarity is often comparable to traditional landline calls, and in some cases, even superior.
**Additional Capabilities of SS7**
SS7 supports a wide array of telephony services, including call forwarding and wireless roaming. It also facilitates caller identification, three-way conference calls, and toll-free/freephone number access. Furthermore, SS7 streamlines the capture of billing information, providing detailed records for subscribers and simplifying the billing process for service providers.
**Detecting SS7 Usage**
It is generally difficult for the average user to determine if a call is routed via SS7. While a slight delay might occur during the switching process, the sound quality remains high, provided the internet connection is stable. Unless you possess advanced technical knowledge, you are unlikely to notice any discernible difference.