The Intelligent Network Application Part (INAP) is a signalling protocol used in the intelligent network

Intelligent network

The Intelligent Network , is the standard network architecture specified in the . It is intended for fixed as well as mobile telecom networks...

 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 points to computer based service independent platform http://www.iec.org/online/tutorials/intern_in/index.html

The ITU

International Telecommunication Union

The International Telecommunication Union is the specialized agency of the United Nations which is responsible for information and communication technologies...

 defines several "capability levels" for this protocol, starting with Capability Set 1 (CS-1).
A typical application for the IN

Intelligent network

The Intelligent Network , is the standard network architecture specified in the . It is intended for fixed as well as mobile telecom networks...

 is a Number Translation service. For example, in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, 0800 numbers are freephone numbers and are translated to a geographic number using an IN platform. The Telephone exchanges decode the 0800 numbers to an IN trigger and the exchange connects to the IN.

The Telephone exchange uses 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...

, SCCP

Signaling Connection and Control Part

The Signalling Connection Control Part is a network layer protocol that provides extended routing, flow control, segmentation, connection-orientation, and error correction facilities in Signaling System 7 telecommunications networks...

 and INAP and in IN terms is a Service Switching Point

Service switching point

In telephony, a service switching point 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 so that the call can be handled...

. It sends an INAP Initial Detection Point (IDP) message to the Service Control Point. The SCP returns an INAP Connect message, which contains a geographic number to forward the call to.

INAP messages are defined using ASN.1

Abstract Syntax Notation One

Data generated at various sources of observation need to be transmitted to one or more locations that process it to generate useful results. For example, voluminous signal data collected by a radio telescope from outer space. The system recording the data and the system processing it later may be...

 encoding.
SCCP

Signaling Connection and Control Part

The Signalling Connection Control Part is a network layer protocol that provides extended routing, flow control, segmentation, connection-orientation, and error correction facilities in Signaling System 7 telecommunications networks...

 is used for the routing. Extended form of INAP is Customised Applications for Mobile Enhanced Logic

Customised Applications for Mobile networks Enhanced Logic

Customised Applications for Mobile networks Enhanced Logic, or CAMEL for short, is a set of standards designed to work on either a GSM core network or UMTS network. They allow an operator to define services over and above standard GSM services/UMTS services...

.
TCAP is used to separate the transactions into discrete units.