This Recommendation provides the number structure and functionality for the three categories of numbers used for international public telecommunication – they are geographic areas, global services and Networks. For each of the categories, it details the components of the numbering structure and the digit analysis required to successfully route the calls. Annex A provides additional information on the structure and function of E.164 numbers. Annex B provides information on network identification, service parameters, calling/connected line identity, dialling procedures and addressing for geographic-based ISDN calls. Specific E.164-based applications which differ in usage are defined in separate Recommendations.