Team Dreams
Sharing knowledge & experiences of SMS,SMPP and SS7
| Home | Our Blogs | SMPP Tutorial | SS7 Experiences | SS7 Resources | SS7 Tutorial | Contact Us |
SS7 Introduction
SS7 is really a control protocol, used to provide instructions to the various elements within a telephony network. These instructions may be how to route a call through the network, what features a caller has subscribed to, or, in the case of number portability, which carrier will be used to handle the call.
SS7 is a sophisticated telecommunications protocol that provides out-of-band signaling and a data interface between phone company switches for the express purpose of reducing congestion in the PSTN (Public Switched Telephone Network).
For example, without SS7, a long distance call is routed through the network to the called party to make their phone ring or before a busy signal can be returned, thereby tying up circuits along the entire path. With SS7, once the call is dialed, the data interface sends a message to the end switch to ring the phone or to check if the called party is busy before the call is routed. If the call is answered, it is then immediately routed though the network, thereby not using the circuits while the phone is ringing or in busy and no-answer situations.
SS7 Usage
- 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
- Intelligent Networks
- Data services like SMS & USSD
Signaling Links
SS7 messages are exchanged between network elements over 56 or 64 kilobit per second (kbps) bi-directional channels called signaling links. Signaling occurs out-of-band on dedicated channels rather than in-band on voice channels.
Compared to in-band signaling, out-of-band signaling provides:
- faster call setup times (compared to in-band signaling using multi-frequency (MF)signaling tones)
- more efficient use of voice circuits
- support for Intelligent Network (IN) services which require signaling to network elements
- without voice trunks (e.g., database systems)
- improved control over fraudulent network usage