What is Signaling System #7 or SS7?

SS7 technology is the basis for modern methods to route telephony traffic with out-of-band signaling. One of the primary benefits of SS7 is global interoperability. SS7 is used to set up and tear down most of the world's public switched telephone network phone calls.

SS7 has the capability to enable all carriers world-wide to cooperate with each other. Global billing, toll-free calling, 900-number services and international wireless call roaming are all features that depend on SS7 technology.

But, to understand SS7, you have to know what out-of-band signaling or communication is. It's the exchange of information that does not take place over the same path as the data transfer, or conversation. It's when a separate digital channel is created - a signaling link - where messages are exchanged at 56 or 64 kilobits per second.

SS7 is characterized by high-speed circuit switching...it's a way to offload data traffic congestion onto a wireless or wireline (or, DSL - a traditional copper telephone line) digital broadband network.