Any identifier within a protocol that must be used in the same manner by all protocol users in order for the protocol to function correctly. Unique identifiers are recorded in authoritative registries to ensure their uniqueness and avoid usage conflicts among protocol users.
The Internet relies on many types of unique identifiers. These include domain names, Internet Protocol (IP) addresses, autonomous system numbers, and port numbers. ICANN’s technical mission involves allocating the unique identifiers that enable the proper operation of the Internet. This function is delivered by Public Technical Identifiers (PTI) as part of its contracts with ICANN to perform the Internet Assigned Numbers Authority (IANA) functions. PTI is an affiliate of ICANN.