In ENUM services, what is often required to map a telephone number to Internet resources?

In ENUM (E.164 Number Mapping) services, the process of mapping a telephone number to Internet resources typically involves the use of Address of Record (AOR) registration. AOR is essential because it provides a way to designate a specific resource associated with a telephone number, such as a SIP URI, facilitating the connection between traditional telephony and VoIP services.

When a telephone number is translated into an ENUM entry, the corresponding AOR indicates where the call should be directed over the Internet, making it easier to reach users who operate through different communication protocols and platforms. This registration process ensures that voice calls can be effectively routed to the correct Internet-based endpoint.

In contrast, secure email delivery, OpenID authentication, and IP address resolution do not directly relate to the function of ENUM in associating phone numbers with Internet resources. While secure email delivery focuses on the integrity and privacy of email communications, OpenID is primarily concerned with user authentication for web applications, and IP address resolution pertains to the conversion of domain names into IP addresses for network routing. These concepts are not integral to the ENUM service's main purpose of linking telephone numbers to internet resources.