Smart grid

In the 1980s, the various American operators tried to solve certain service-related problems by modifying the programs running on each switch in the network. Network operators wishing to introduce a new service were heavily dependent on their suppliers, who were the only ones able to modify the highly complex programs running on their switches. Since the supplier is in a position of strength, he can charge a very high price for the program modification requested. For the operator, these costs are multiplied by the number of manufacturers supplying switches for his network. Once the necessary programs are available, they need to be introduced into all the switches in the network if the service is to be available everywhere. Since a network can consist of several hundred switches, this operation can be not only costly, but also time-consuming.

It is usually estimated that it takes 3 to 5 years from the decision to introduce a new service to its actual implementation in the network. These timescales do not allow an operator to react quickly to a customer's request for a particular service. Today, 6 months is considered the maximum timeframe.

On the other hand, some services require the switch to process information that is not local, but common to all switches in the network. For example, the Numéro Vert application, which enables a caller to make a free call, relies on the translation of a logical number with a specific prefix (0800 in France) into a real destination number. The translation table is global to all switches. Duplicating such a table across all the switches in the network involves very difficult management to guarantee its consistency. On the other hand, having a central node storing this table and accessible by all switches is a simple and inexpensive solution. This is how the Green Number was introduced in the USA. A node called the service control point (SCP) is dedicated to processing the number translation. In this way, the network is enriched with a new functionality, and because of its ability to process information and offer a more advanced service than the basic call, it is described as "intelligent".

In the architecture of the Intelligent Network (IN), the SCP acts as the master, while the switches (SSP, "service switching point") are the slaves. This centralized principle is well suited to services requiring a single database. What's more, only the SCP is updated when a new service is installed.

The execution of a Green Number service can be described by the following steps: a caller picks up the receiver and dials the desired Green Number (logical number) (0800 25 26 27). The SSP, detecting the "0800" prefix, decides to stop all processing of this call, and asks the SCP for instructions. The...