Short for Signaling System 7, a telecommunications protocol defined by the International Telecommunication Union (ITU) as a way to offload PSTN data traffic congestion onto a wireless or wireline digital broadband network.
SS7 is characterized by high-speed circuit switching and out-of-band signaling using Service Switching (SSPs), Signal Transfer Points (STPs), and Service Control Points (SCPs) (collectively referred to as signaling points, or SS7 nodes). Out-of-band signaling is signaling that does not take place over the same path as the data transfer (or conversation)--a separate digital channel is created (called a signaling link), where messages are exchanged between network elements at 56 or 64 kilobit per second.
SS7 architecture is set up in a way so that any node could exchange signaling with any other SS7-capable node, not just signaling between switches that are directly connected.
The SS7 network and protocol are used for:
- basic call setup, management, and tear down
- wireless services such as personal communications services (PCS), wireless roaming, and mobile subscriber authentication
- local number portability (LNP)
- toll-free (800/888) and toll (900) wireline services
- enhanced call features such as call forwarding, calling party name/number display, and three-way calling
- efficient and secure worldwide telecommunications