Question: What is a requirement for an APN Network Identifier with more than one label to ensure uniqueness within or between GPRS/EPS Public Land Mobile Networks (PLMNs)?
Option 1: It must start with a Reserved Service Label.
Option 2: It should correspond to an Internet domain name, allocated by the PLMN if it officially reserved this name in the Internet domain.
Option 3: It must end with ".gprs" to indicate GPRS service.
Option 4: It shall contain exactly three labels for global uniqueness.
Explanation: To guarantee uniqueness of APN Network Identifiers within or between GPRS/EPS PLMNs, an identifier with more than one label must correspond to an Internet domain name. This ensures uniqueness since the allocation of such names is centrally managed on the internet, preventing duplicate assignments across different networks.