http://www.rfc-editor.org/rfc/rfc5273.txt
RFC 5273: Certificate Management over CMS (CMC): Transport Protocols, J. Schaad, M. Myers2008-06-01T23:00:00-00:00This document defines a number of transport mechanisms that are used to move CMC (Certificate Management over CMS (Cryptographic Message Syntax)) messages. The transport mechanisms described in this document are HTTP, file, mail, and TCP. [STANDARDS-TRACK]