C Reference Definition of Directory Object Classes and Attributes
D Security Threats
D.1 Masquerade
D.2 Message Sequencing
D.3 Modification of Information
D.4 Denial of Service
D.5 Repudiation
D.6 Leakage of Information
D.7 Other Threats
E Provision of Security Services in Recommendation X.411
F Differences Between CCITT Recommendation and ISO Standard
G Index
Section One - Introduction
0. Introduction
This Recommendation is one of a set of Recommendations for Message Handling. The
entire set provides a comprehensive blueprint for a Message Handling System (MHS)
realized by any number of cooperating open systems.
The purpose of an MHS is to enable users to exchange messages on a store-and-forward
basis. A message submitted on behalf of one user, the originator, is conveyed by the
Message Transfer System (MTS) and subsequently delivered to the agents of one or more
additional users, the recipients. Access units (AUs) link the MTS to communication
systems of other kinds (e.g., postal systems). A user is assisted in the preparation,
storage, and display of messages by a user agent (UA). Optionally, he is assisted in
the storage of messages by a message store (MS). The MTS comprises a number of message
transfer agents (MTAs) which collectively perform the store-and-forward message
transfer function.
This Recommendation specifies the overall architecture of the MHS and serves as a
technical introduction to it.
The text of this Recommendation is the subject of joint CCITT-ISO agreement. The
corresponding ISO specification is ISO 10021-2.
1. Scope
This Recommendation defines the overall architecture of the MHS and serves as a
technical introduction to it.
Other aspects of Message Handling are specified in other Recommendations. A non-technical overview of Message Handling is provided by Recommendation X.400. The
conformance testing of MHS components is described in Recommendation X.403. The
conventions used in the definition of the abstract services provided by MHS components are
defined in Recommendation X.407. The detailed rules by which the MTS converts the
contents of messages from one EIT to another are defined in Recommendation X.408. The
abstract service the MTS provides and the procedures that govern its distributed operation
are defined in Recommendation X.411. The abstract service the MS provides is defined
in Recommendation X.413. The application protocols that govern the interactions of
MHS components are specified in Recommendation X.419. The Interpersonal Messaging
System, an application of Message Handling, is defined in Recommendation X.420. Telematic
access to the Interpersonal Messaging System is specified in Recommendation T.330.
The CCITT Recommendations and ISO International Standards on Message Handling are
summarized in Table 1/X.402.
Table .T.:1/X.402 Specifications for Message Handling Systems
+-------+--------+-------------------------------------------+ | CCITT | ISO |
SUBJECT MATT R | +- Introduction -+--------------------------
------------------+ | X.400 | 8505-1 | Service and system overview | |