Intelligent Networks
An intelligent network (IN) is a service-independent telecommunications network. That is, intelligence is taken out of the switch and placed in computer nodes that are distributed throughout the network. This provides the network operator with the means to develop and control services more efficiently. New capabilities can be rapidly introduced into the network. Once introduced, services are easily customized to meet individual customer's needs.
This tutorial discusses how the network has evolved from one in which switch-based service logic provided services to one in which service-independent advanced intelligent network (AIN) capabilities allow for service creation and deployment.
As the IN evolves, service providers will be faced with many opportunities and challenges. While the IN provides a network capability to meet the ever-changing needs of customers, network intelligence is becoming increasingly distributed and complicated. For example, third-party service providers will be interconnecting with traditional operating company networks. Local number portability (LNP) presents many issues that can only be resolved in an IN environment to meet government mandates. Also, as competition grows with companies offering telephone services previously denied to them, the IN provides a solution to meet the challenge.
1. Network Evolution
Prior to the mid-1960s, the service logic, as shown in Figure 1, was hardwired in switching systems. Typically, network operators met with switch vendors, discussed the types of services customers required, negotiated the switching features that provided the services, and finally agreed upon a generic release date for feature availability. After this, the network operator planned for the deployment of the generic feature/service in the switching network fabric.
This process was compounded for the network operator with switching systems from multiple vendors. As a result, services were not offered ubiquitously across an operator's serving area. So, a customer in one end of a city, county, or state may not have had the same service offerings as a person in another part of the area.
Also, once services were implemented, they were not easily modified to meet individual customer's requirements. Often, the network operator negotiated the change with the switch vendor. As a result of this process, it took years to plan and implement services.
This approach to new service deployment required detailed management of calling patterns, providing new trunk groups to handle calling patterns. As customer calling habits changed (longer call lengths, larger calling areas, and multiple lines in businesses and residences) the demand on network operators increased.
Stored Program Control (SPC)
In the mid-1960s, stored program control (SPC) switching systems were introduced. SPC was a major step forward because now service logic was programmable where, in the past, the service logic was hardwired. As a result, it was now easier to introduce new services. Nevertheless, this service logic concept was not modular. It became increasingly more complicated to add new services because of the dependency between the service and the service-specific logic. Essentially, service logic that was used for one service could not be used for another service. As a result, if customers were not served by a SPC switching system, new services were not available to them.
Another aspect of the traditional services offerings was the call setup information?that is, the signaling and call supervision that takes place between switching systems and the actual call. When a call was set up, a signal and talk path used the same common trunk from the originating switching system to the terminating switching system. Often there were multiple offices involved in the routing of a call. This process seized the trunks in all of the switching systems involved. Hence, if the terminating end was busy, all of the trunks were set up unnecessarily.
The network took a major leap forward in the mid-1970s with the introduction of the common channel signaling network (CCSN), or SS7 network for short. Signaling system number 7 (SS7) is the protocol that runs over the CCSN. The SS7 network consists of packet data links and packet data switching systems called signaling transfer points (STPs).
The SS7 network (see Figure 2) separates the call setup information and talk path from the common trunk that runs between switching systems. The call setup information travels outside the common trunk path over the SS7 network. The type of information transferred included permission for the call setup and whether or not the called party was busy.
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