Service Control Point

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A Service Control Point ( SCP ) is a network element of the telephone network with which additional services can be implemented. Functions are outsourced in the SCP which could not be implemented in the switching nodes (i.e. switching centers in the fixed network or MSC in the mobile radio network ) or only with great effort . The functions implemented in this way are also summarized under the keyword Intelligent Network (IN).

Services

The SCP supports the establishment of the call during a telephone call. Functions that can be supported are for example:

  • Manage value-added services (for example 0137, 0180, 0800 and 0900 numbers)
  • Provision of subscriber databases and handling of database queries
  • Management of announcement services and playback of announcements
  • Provision of closed user groups (CUG), for example to implement internal company networks ( corporate network ) in the public telephone network

The SCP receives its work order from the switching centers (in the fixed network) or mobile switching center (in the cellular network). While a telephone call is being set up, so-called IN triggers can be set up in which the standard call set-up is interrupted and a request to the SCP is started instead. The call setup is then continued with the result of the SCP request. IN trigger points can be, for example:

Possible SCP service: "Red telephone", the SCP reports back the long number of the preset participant, whereupon the preset participant is called without dialing.
  • The calling party dialed a number.
Possible SCP service: "Speed dial translation ", if the calling subscriber belongs to a "closed user group", speed dial numbers are automatically translated into the extension number of the telephone system to which the subscriber belongs.
Possible SCP service: "Charge announcement"; For example, when making international calls, first play an announcement to the subscriber about how expensive this call will be and only carry out the call after confirmation.
  • A call from another telephone company arrives in your own telephone network.
Possible SCP service: "Number portability"; Inquire in the subscriber database whether the call number belongs to a subscriber of your own and if not, break off the call
Possible SCP service: "Number portability in the local network"; Inquire in a subscriber database to which local exchange the subscriber is really connected to and direct the call there .
  • The called party picks up.
Possible SCP service: "Prepaid credit management"; During the call, deduct the call charges from the calling party's credit and end the call if there is insufficient credit.

Interfaces

All operations of the SCP are signaling operations (support for call setup and cleardown, call data checking). For this reason, the SCP is only connected to the signaling network of a telephone network via lines of the Signaling System 7 (SS7). In larger telephone networks, the SCP communicates directly with the SS7 switching nodes ( Signaling Transfer Points ). The SS7 protocols used for this are INAP and CAMEL .

In addition to SS7, some SCPs can also be triggered using protocols from the Internet protocol family , such as OPINEXA . These contain the same functionalities as the SS7 protocols INAP or CAMEL.

In addition to the SS7 interfaces, the SCP also has IP interfaces via which, for example, subscriber databases of the SCP can be managed and updated.

literature

  • JE Flood (Ed.): Telecommunication Networks. 2nd Edition, The Institution of Electrical Engineers, London 1997, ISBN 0-85296-884-1 .
  • Volker Jung, Hans-Jürgen Warnecke (Hrsg.): Handbook for telecommunications. Springer Verlag, Berlin / Heidelberg 1998, ISBN 978-3-642-97703-9 .
  • Wolfgang Effelsberg, Hans W. Meuer, Günter Müller (eds.): Communication in distributed systems. Springer Verlag, Berlin / Heidelberg, ISBN 978-3-540-53721-2 .
  • Peter R. Gerke: Digital communication networks. Springer Verlag, Berlin / Heidelberg 1991, ISBN 978-3-642-93459-9 .
  • Martin Werner: Networks, protocols, interfaces and communication. 1st edition, Friedrich Vieweg & Sohn Verlag, Braunschweig 2005, ISBN 3-528-03998-1 .

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