OCSP Extensions to IKEv2
While IKEv2 supports public key based authentication (PKI), the corresponding use of in-band CRLs is problematic due to unbounded Certificate Revocation List (CRL) size. The size of an Online Certificate Status Protocol (OCSP) response is however well-bounded and small. This document defines the "OCSP Content" extension to IKEv2. A CERTREQ payload with "OCSP Content" identifies zero or more trusted OCSP responders and is a request for inclusion of an OCSP response in the IKEv2 handshake. A cooperative recipient of such a request responds with a CERT payload containing the appropriate OCSP response. This content is recognizable via the same "OCSP Content" identifier. When certificates are used with IKEv2, the communicating peers need a mechanism to determine the revocation status of the peer's certificate. OCSP is one such mechanism. This document applies when OCSP is desired and security policy prevents one of the IKEv2 peers from accessing the relevant OCSP responder directly. Firewalls are often deployed in a manner that prevents such access by IKEv2 peers outside of an enterprise network.