Intelligent Network

Description

The Intelligent Network (IN) is a service architecture framework defined by 3GPP, based on earlier ITU-T standards, which introduces a fundamental separation between the basic call/service switching functions and the advanced service logic. This separation is achieved through a distributed network architecture where service control is centralized in dedicated network nodes, while call switching remains in the traditional switching nodes. The core principle is the use of standardized triggers, known as Detection Points (DPs), embedded within the Basic Call State Model (BCSM) of a switch or call control function. When a call event matches a configured trigger, the switch suspends call processing and sends a query, via a standardized protocol, to an external entity containing the service logic.

The key architectural components of IN include the Service Switching Point (SSP), which is the switching node (like an MSC or GMSC) equipped with IN capabilities; the Service Control Point (SCP), which is a dedicated server hosting the service logic programs (SLPs) and databases; and the Service Data Point (SDP), which stores subscriber and service-related data. Communication between the SSP and SCP is standardized, primarily using the Intelligent Network Application Protocol (INAP). The service logic on the SCP processes the query, executes the service (e.g., number translation, credit checking), and returns instructions (e.g., connect, play announcement, collect digits) to the SSP to resume and complete the call.

IN's role in the network is to provide a vendor-independent, flexible platform for value-added services. It allows network operators to deploy and manage services centrally, reducing time-to-market and operational costs. The architecture supports services like Customized Applications for Mobile network Enhanced Logic (CAMEL) for mobile networks, which extends IN principles to provide operator-specific services like prepaid, location-based services, and call screening across different network domains and even while roaming. IN forms the foundational concept for later service delivery platforms and the separation of control and user planes seen in modern networks.

Purpose & Motivation

The Intelligent Network was created to solve the critical problem of slow and costly service innovation in traditional telephony networks. Historically, new telecommunication services were tightly integrated into the proprietary software of circuit switches from vendors like Ericsson, Nokia, or Siemens. To introduce a service like freephone (800-number) or televoting, operators had to request vendor-specific software upgrades for each switch, a process that was time-consuming, expensive, and led to vendor lock-in. This stifled competition and delayed the rollout of new revenue-generating features.

The IN architecture addressed these limitations by standardizing the interface between the switching function and the service logic function. This decoupling meant that service logic could be developed and hosted on centralized, standard computing platforms (SCPs) independent of the switch vendors. Operators could now create and modify services rapidly by updating logic and data on the central SCPs, without needing to touch every individual switch in the network. This shift not only accelerated service deployment but also fostered a more open ecosystem where third-party service providers could potentially develop applications for the network.

In the context of 3GPP, IN principles were essential for bringing intelligent services to GSM and later mobile networks. The need for advanced, operator-controlled services that worked seamlessly in home networks and while roaming was a key driver. The CAMEL standard, which is an implementation of IN for mobile networks, was developed to provide services like prepaid roaming, which was commercially crucial but impossible with traditional switch-based logic. Thus, IN provided the architectural blueprint for the programmable, service-aware core network that underpins modern telecommunications.

Key Features

• Separation of service control from call switching (Service Switching Function vs. Service Control Function)
• Standardized trigger mechanisms (Detection Points) within the Basic Call State Model
• Centralized service logic execution on Service Control Points (SCPs)
• Use of the Intelligent Network Application Protocol (INAP) for communication
• Support for service-independent building blocks (SIBs) for service creation
• Enables rapid deployment of value-added services like Number Translation, Freephone, and Prepaid

Evolution Across Releases

Defining Specifications