Apologies for the very late response / answer.
Signalling is a fundamental part of Telecommunication.
Signalling is the main vehicle that is used to initiate, maintain and clear down Telecommunication circuits / resources. In the past analog signalling (e.g. R2, Multi-Frequency
Compelled (MFC), etc..) was used with Analag Switches (e.g. Crossbar, Strowger, TXE, etc..).
With the requirements for ISDN – Integrated Services Digital Network – and enhanced Services (e.g. Calling Line Identity, Call Waiting, Three Party Calls, Call Forwarding based on busy / no response, Ring Back When Free, Centrex, etc..) the Local Switching Exchanges and the signalling had to be modernised. This required the fast adoption of Stored Program Control (SPC) Telephone Exchanges (“Switches”) with a digital signalling system. SS7 – Signalling System
Number 7 – proved to be a versatile signalling solution for Telecommunication Networks. SS7 could cater for Connection-Orientated
or Connection-Less signalling. Connection Orientated was used to secure resources (Time Slots) for traditional Telephony Calls.
Connection-Less signalling was used with applications that would make “dips” into a Database. Good examples is with Intelligent Networks (IN) and
HLR (Home Location Register).
SS7 is now conveyed via IP – Internet Protocol. Telecommunication Networks now use Sigtran – Signalling Transport (IP) – to convey SS7.
VBR/ Wallis Dudhnath