SS7 is Signalling System Number 7. It is a Signalling system that was Standardised, designed and implemented as a part of the move from Analog Switches to Digital Switches.
Regardless of SS7, Signalling is used to initiate, maintain and cleardown a telephony session.
A Switch is basically a traditional Telephone Exchange. For a Digital Switch a “software Group Switch” using Control software will help to connect incoming / outgoing Time Slots. SS7 has been the backbone or the central nervous system for Digital Telecommunication Networks.
The main reason to enhance Analog Switches and the Analog (e.g. Voice Frequency) signalling were:-
-Fraud: With Analog Signalling it was easy to mimic the Voice Frequency signals so that frauds (extensive free calls) could be made. In fact, the first generation of Hackers were the
Phone Phreakers using their “blue boxes” to operate Telecommunication Equipment from the once ubiquitous
Payphones.
-Advanced Services: Analog Systems supported POTS – Plain Old Telephony Services. The move to Digital SS7 Signalling and the introduction of Digital Switches meant that PANS – Pretty Amazing Network Services – could be deployed.
Look at ISDN and the numerous Services based around Calling Identity, Ring Back, Call Forwarding, Charging, etc..Services.
SS7 is a message based Signalling system that aligns with OSI’s classic stack. GSM Network solutions are based
on SS7 and ISDN signalling.
VBR/ Wallis Dudhnath