X.400 1988 to 1984 downgrading (RFC1328)
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2000-Sep-12
Internet Society Requests For Comment (RFCs)
This 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.
Network Working Group S. Hardcastle-Kille
Request for Comments: 1328 University College London
X.400 1988 to 1984 downgrading
Status of this Memo
This RFC specifies an IAB standards track protocol for the Internet
community, and requests discussion and suggestions for improvements.
Please refer to the current edition of the "IAB Official Protocol
Standards" for the standardization state and status of this protocol.
Distribution of this memo is unlimited.
This 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
This specification is not tutorial. COSINE Study 8.2 by J.A.I.
Craigie gives a useful overview [Cra88].
1. The need to Downgrade
It is expected that X.400(1988) systems will be extensively deployed,
whilst there is still substantial use of X.400(1984). If 1988
features are to be used, it it important for there to be a clear
approach to downgrading. This document specifies an approach to
downgrading for the Internet and COSINE communities. As 1988 is a
strict superset of 1984, the mapping is a one-way problem.
2. Avoiding Downgrading
Perhaps the most important consideration is to configure systems so
as to minimise the need for downgrading. Use of 1984 systems to
interconnect 1988 systems should be strenuously avoided.
In practice, many of the downgrading issues will be avoided. When a
1988 originator sends to a 1984 recipient, 1988 specific features
will not be used as they will not work! For distribution lists with
1984 and 1988 recipients, messages will tend to be "lowest common
In general there is a problem with O/R addresses which use 88
specific features. The X.419 downgrade approach will mean that
addresses using these features cannot be specified from 84 systems.
Worse, a message originating from such an address cannot be
transferred into X.400(1984). This is unacceptable. Two approaches
are defined. The first is a general purpose mechanism, which can be
implemented by the gateway only. The second is a special purpose
mechanism to optimise for a form of X.400(88) address which is
expected to be used frequently (Common Name). The second approach
requires cooperation from all X.400(88) UAs and MTAs which are
involved in these interactions.
3.1 General Approach
The first approach is to use a DDA "X400-88". The DDA value is an
std-or encoding of the address as defined in RFC 1327 [Kil92]. This
will allow source routing through an appropriate gateway. This
solution is general, and does not requir...