​Study Group 2 is home to Recommendation ITU-T E.164, the numbering standard which has played a central role in shaping the telecom networks of today. ITU-T E.164 provides the structure and functionality of telephone numbers, and without it we would not be able to communicate internationally. In recent years SG2 has worked on ENUM, an Internet Engineering Task Force (IETF) protocol for entering E.164 numbers into the Internet domain name system (DNS).

An equally important product of SG2 is Recommendation ITU-T E.212 which describes a system to identify mobile devices as they move from network to network. International mobile subscriber identity (IMSI) is a critical part of the modern mobile telecoms system, allowing the identification of a roaming mobile terminal in a foreign network and subsequently the querying of the home network for subscription and billing information.