Signaling System No.7 (SS7)

Definition - What does Signaling System No.7 (SS7) mean?

Signaling System No.7 (SS7) is a set of telephone signaling protocols that are used to set up and tear down most of the world’s public switched network calls. Other functions include number translation, prepaid billing capabilities and short message service (SMS). SS7 is defined by the International Telecommunication Union. SS7 is characterized by high-speed circuit switching and out-of-band signaling using service switching points, signal transfer points and service control points.

In North America, SS7 is often called a common channel signaling system (CCSS7). In some European countries, it is also called CCITT No.7 (C7), No.7 or common channel interoffice signaling 7 (CCIS7).

Techopedia explains Signaling System No.7 (SS7)

SS7 is a separate signaling network used in Class 4 and Class 5 voice switches. SS7 networks and protocols are use for:

  • Basic call setup, management and tear down
  • Wireless services such as roaming, mobile subscriber authentication and personal communications services
  • Local number portability
  • Toll-free and toll-wire line services
  • Enhanced call features such as calling party name and number display, call forwarding and three-way calling
  • Efficient and secure worldwide telecommunications

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