The SS7 (Signalling System Number 7) is an
ITU standard for signalling in telephone networks.
SS7
(Signalling System Number 7) is an international telecommunications standard developed
by the International Telecommunication Union (ITU) Telecommunication Sector (ITU-T). The
SS7 standard defines the procedures and protocols by
which elements in the public switched telephone network (PSTN) exchange
out-of-band signalling information over a digital signalling network. The protocols
and procedures define such things as call set-up and tear-down,
call management, call routing, call forwarding, display of calling party
number, wireless services, and so on. The SS7
standard refers to out-of-band signalling, that is signalling that is
not sent down the same channel as the voice call.
In
GSM, the SS7 (Signalling System Number 7) is
used for all signalling on all links except for the
air interface (or radio interface).