3. Standardization

As early as the mid-1980s, work carried out by international standards bodies led to the publication of the first recommendations dedicated to ISDN.

In order to cover all the aspects inherent in ISDN, and to allow each of them to evolve, an organization into six subsets or sets of recommendations has been adopted, as shown below:

• general description, terminology and modeling methods (series I.100) ;

• service aspects (series I.200) ;

• network aspects (I.300 series) ;

• ISDN user-network interfaces (I.400 series) ;

• interfaces between networks (I.500 series) ;

• maintenance principles (I.600 series).

The chosen structure...