Question: What is the maximum recommended length (in characters) for the realm part of a permanent user identity in a non-3GPP access scenario to ensure compatibility with standard RADIUS equipment?
Option 1: 55 characters, to accommodate various encoding schemes
Option 2: 40 characters, to prevent truncation in RADIUS Access-Requests
Option 3: 72 characters, matching the maximum NAI length for EAP-AKA/EAP-AKA’
Option 4: 23 characters, mirroring the length of temporary identities
Explanation: The correct answer is Option 2 because, according to the specifications, the User-Name attribute in a RADIUS Access-Request has a standard length up to 63 octets (characters), and considering the structure of a NAI (username part + realm part), to ensure the entire identity can be handled correctly, the realm part should not exceed 40 characters, especially when the username part could potentially use up to 23 characters in the case of temporary identities. This ensures compatibility with standard RADIUS equipment.