IN
IN was invented to introduce new features and services over existing telco nodes without impact of their limited service capabilities. As does parlay (tried to do as it is not so popular as IN). But IN has got at the purpose of manufactorers - those are to blame for complicated standard.
It started from capability set 1 CS1 then CS2, Camel with currently increasing version numbers ...
This standard for sure was designed to preserve big companies area from small companies impact.
(it is profi(t)bus of the telco)
IN is not part of SS7 , of course its operations are sit on top mtp sccp tcap stack, but it is not what the ss7 is.
As example of IN implementations :
prepaid
vpn
televoting system
alert call
call back
....
IN nodes are :
- SCP is where the service logic run
- SSF is a mean to control call under supervision of SCP (where IN script is ran)
- SRF is imxo something to offer announcement and may be more facilities
-SDP is for database purposes in IN network.