Telephone numbers are designed by the national telecom regulators according to the E.164 numbering plan (see the practice note on the E.164 numbering plan). For technical reasons numbers have been designed according to their geographical location in such a way that subscribers connected to the same local exchange share the same area code.
A numbering plan can be either open or closed. In an open numbering plan special arrangements are made for local calls, so the dialer only needs to include the area code in long distance or international calls. In a closed numbering plan the same number of digits must be dialed in all national calls.
Most numbering plans reserve special series for different kinds of calls or services. For instance special prefixes are used for mobile numbers in India and in Brazil. Each operator may also have its own prefixes, as in Colombia. Many countries have reserved 800 and 900 numbers for freephone and value added services.
Thus numbers do not only serve as a tool for unique identification, they also provide information on location, type of service etc. This information is often necessary in order to know the tariff for the call.
The international regulatory framework for administration of IP-addresses is headed by ICANN and completely different from those in the E.164 numbering plan. For more information about the international regulatory framework for the administration of IP-addresses, please see the Practice Note on ICANN. At the national level similar models of self regulation have often been established in order administrate the national allocation of IP-addresses and domain names.