Service switching point
Encyclopedia
In telephony
, a service switching point (SSP) is the telephone exchange
that initially responds, when a telephone caller dials a number, by sending a query to a central database called a service control point
(SCP) so that the call can be handled. The service switching point uses the Signalling System 7
(SS7) protocols which are responsible for the call setup, management, and termination with other service switching points.
architecture, service functionality (e.g. UK translation of 0800 non-geographic telephone numbers) is being removed from the actual telephone exchange and devolved out into other computer nodes. In this new architecture, the telephone exchange is known as an SSP and the node that contains the services (and hence controls the progression of a call) is known as service control point
(SCP).
numbers).
An SSP telephone exchange receives a call to an 0800 number. This causes a trigger within the SSP that causes an SCP (Service Control Point) to be queried using SS7 protocols ( INAP
, TCAP
). The SCP responds with a geographic number, e.g. 0121 XXX XXXX, and the call is actually routed to a phone.
By this architecture:
Telephony
In telecommunications, telephony encompasses the general use of equipment to provide communication over distances, specifically by connecting telephones to each other....
, a service switching point (SSP) is the telephone exchange
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
that initially responds, when a telephone caller dials a number, by sending a query to a central database called a service control point
Service Control Point
A service control point is a standard component of the Intelligent Network telephone system which is used to control the service. Standard SCPs in the telecom industry today are deployed using SS7, Sigtran or SIP technologies. The SCP queries the service data point which holds the actual...
(SCP) so that the call can be handled. The service switching point uses the Signalling System 7
Signalling System 7
Signalling System No. 7 is a set of telephony signaling protocols which are used to set up most of the world's public switched telephone network telephone calls. The main purpose is to set up and tear down telephone calls...
(SS7) protocols which are responsible for the call setup, management, and termination with other service switching points.
Relationship between SSP and SCP
With the introduction of the Intelligent NetworkIntelligent network
The Intelligent Network , is the standard network architecture specified in the . It is intended for fixed as well as mobile telecom networks...
architecture, service functionality (e.g. UK translation of 0800 non-geographic telephone numbers) is being removed from the actual telephone exchange and devolved out into other computer nodes. In this new architecture, the telephone exchange is known as an SSP and the node that contains the services (and hence controls the progression of a call) is known as service control point
Service Control Point
A service control point is a standard component of the Intelligent Network telephone system which is used to control the service. Standard SCPs in the telecom industry today are deployed using SS7, Sigtran or SIP technologies. The SCP queries the service data point which holds the actual...
(SCP).
Example of a 0800 number translation service
In the UK 08XXX numbers are non-geographic numbers – that is, the number does not refer to a telephone number in any particular region of the UK. To route a call to such an 08XXX number, the number must be translated into a geographic number (e.g. 0121 XXX XXXX for BirminghamBirmingham
Birmingham is a city and metropolitan borough in the West Midlands of England. It is the most populous British city outside the capital London, with a population of 1,036,900 , and lies at the heart of the West Midlands conurbation, the second most populous urban area in the United Kingdom with a...
numbers).
An SSP telephone exchange receives a call to an 0800 number. This causes a trigger within the SSP that causes an SCP (Service Control Point) to be queried using SS7 protocols ( INAP
INAP
The Intelligent Network Application Part is a signalling protocol used in the intelligent network architecture. It is part of the SS7 protocol suite, typically layered on top of TCAP.It can also be termed as logic for controlling telecommunication services migrated from traditional switching...
, TCAP
Transaction Capabilities Application Part
Transaction Capabilities Application Part, from ITU-T recommendations Q.771-Q.775 or ANSI T1.114 is a protocol for Signalling System 7 networks. Its primary purpose is to facilitate multiple concurrent dialogs between the same sub-systems on the same machines, using Transaction IDs to differentiate...
). The SCP responds with a geographic number, e.g. 0121 XXX XXXX, and the call is actually routed to a phone.
By this architecture:
- 08XXX (non-geographic numbers) can be set up in a few SCP nodes rather than having to be set up in every telephone exchange in the country.
- geographic numbers can be hidden
- revenue can be generated by non-telecoms companies from people making telephone calls to services – e.g. telephone voting
External links
- SS7 Tutorial – Signalling architecuture, including SSP description. [Link Dead]