What security standard is often used with Internet Key Exchange (IKE)?

The correct choice is IPSEC because it directly collaborates with Internet Key Exchange (IKE) to secure Internet Protocol communications. IKE is primarily responsible for establishing a secure and authenticated channel for the negotiation of cryptographic keys needed for secure communication. It is a part of the IP Security (IPSEC) suite, which is designed to ensure the confidentiality, integrity, and authenticity of data packets transmitted over an IP network.

IPSEC provides the necessary framework for encrypting and authenticating the data that IKE helps to secure by managing the keys used in the process. This tight integration between IKE and IPSEC makes IPSEC the obvious choice when discussing security standards relevant to IKE, as they work synergistically to enhance the overall security of IP communications.

The other options may align with various security concepts but do not work in conjunction with IKE in the same manner. SSL, for instance, is primarily designed for securing web traffic, OPSEC is a broader operational framework, and Kerberos is a network authentication protocol which does not relate directly to the key exchange process for IP communications like IKE does with IPSEC.