Table of Contents:

Definition and Overview

1. What is Signaling?

2. What is Out-of-Band Signaling?

3. Signaling Network Architecture

4. The North American Signaling Architecture

5. Basic Signaling Architecture

6. SS7 Link Types

7. Basic Call Setup Example

8. Database Query Example

9. Layers of the SS7 Protocol

10. What Goes Over the Signaling Link

11. Addressing in the SS7 Network

12. Signal Unit Structure

13. What are the Functions of the Different Signaling Units?

14. Message Signal Unit Structure

Self-Test

Glossary

PDF of this tutorial

As users of the PSTN, we exchange signaling with network elements all the time. Examples of signaling between a telephone user and the telephone network include: dialing digits, providing dial tone, accessing a voice mailbox, sending a call-waiting tone, dialing *66 (to retry a busy number), etc.

SS7 is a means by which elements of the telephone network exchange information. Information is conveyed in the form of messages. SS7 messages can convey information such as:

• I’m forwarding to you a call placed from 212-555-1234 to 718-555-5678. Look for it on trunk 067.
• Someone just dialed 800-555-1212. Where do I route the call?
• The called subscriber for the call on trunk 11 is busy. Release the call and play a busy tone.
• The route to XXX is congested. Please don’t send any messages to XXX unless they are of priority 2 or higher.
• I’m taking trunk 143 out of service for maintenance.

SS7 is characterized by high-speed packet data and out-of-band signaling.