Question: In the context of Private network access via Untrusted non-3GPP Access networks using S2b, which of the following statements about authentication protocols supported by the External AAA Server is accurate?
Option 1: Both PAP and CHAP are supported for all types of accesses including 3GPP, S2a, S2b, and I-WLAN.
Option 2: EAP is exclusively used for S2b accesses, while PAP and CHAP are reserved for 3GPP and S2a accesses.
Option 3: The External AAA Server may support either PAP or CHAP for S2b, but EAP is specifically supported for I-WLAN, not for S2b or S2a accesses.
Option 4: Only CHAP is standardized for use with S2b, as PAP is considered obsolete from a security standpoint and EAP is not applicable.
Explanation: This option accurately reflects the nuances of authentication protocol support for different access types. It correctly identifies that for S2b accesses via Untrusted non-3GPP networks, either PAP or CHAP may be used (with a security caveat about PAP), and distinguishes this from EAP's applicability, which is limited to I-WLAN according to the referenced specifications. This requires an understanding of the specific security protocols and their applications within telecom networks, particularly in the context of non-3GPP accesses and the S2b interface.