Question: For S1-MME and X2-C interfaces in an E-UTRAN, what is the mandatory security implementation on the eNB side to protect control plane traffic as per Network Domain Security (NDS) specifications?
Option 1: Transport mode IPsec with IKEv1 certificate-based authentication
Option 2: Tunnel mode IPsec with IKEv2 pre-shared key authentication
Option 3: Tunnel mode IPsec with IKEv2 certificates based authentication
Option 4: Integrity protection only according to NDS/IP without encryption
Explanation: This is because the question's context requires protection of sensitive data on S1-MME and X2-C interfaces, necessitating both integrity and confidentiality. Tunnel mode IPsec provides this comprehensive protection, and IKEv2 certificates based authentication is specified for these interfaces to ensure secure key exchange and authentication, aligning with Network Domain Security (NDS) specifications for robust control plane protection in E-UTRAN.