Although theInternational Telecommunication Union (ITU) has attempted to promote common standards among nation states,numbering plans take different formats in different parts of the world. For example,the ITU recommends that member states adopt 00 as their international access code. However,as these recommendations are not binding on member states,some have not,such as theUnited States,Canada,and other countries and territories participating in theNorth American Numbering Plan.The international numbering plan establishescountry codes,that is,area codes that denote nations or groups of nations. TheE.164 standard regulatescountry codes at the international level and sets a maximum length limit on a full international phone number (15 digits). However,it is each country's responsibility to define the numbering within its own network. As a result,regional area codes may be: