http://www.rfc-editor.org/rfc/rfc1328.txt
RFC 1328: X.400 1988 to 1984 downgrading, S. Hardcastle-Kille1992-05-01T23:00:00-00:00This document considers issues of downgrading from X.400(1988) to X.400(1984) [MHS88a, MHS84]. Annexe B of X.419 specifies some downgrading rules [MHS88b], but these are not sufficient for provision of service in an environment containing both 1984 and 1988 components. This document defines a number of extensions to this annexe. [STANDARDS-TRACK]