CONTENTS

Page

Recommendation X.402 - Message handling systems: overall

architecture ................................. 1

Recommendation X.403 - Message handling systems: conformance

testing ...................................... 1

Recommendation X.407 - Message handling systems: abstract service

definition conventions ....................... 1

Recommendation X.402

MESSAGE HANDLING SYSTEMS OVERALL ARCHITECTURE

The establishment in various countries of telematic services and computer-based store-and-forward message services in association with public data networks creates a need to produce standards to facilitate international message exchange between subscribers to such services.

The CCITT,

considering

(a)	the need for Message Handling Systems;

(b)	the need to transfer and store messages of different types;

(c)	that Recommendation X.200 defines the Reference Model of Open Systems Interconnection for CCITT applications;

(d)	that Recommendations X.208, X.217, X.218, and X.219 provide the foundation for CCITT applications;

(e)	that the X.500-series Recommendations define Directory Systems;

(f)	that Message Handling Systems are defined in a series of Recommendations: X.400, X.402, X.403, X.407, X.408, X.411, X.413, and X.419;

(g)	that Interpersonal Messaging is defined in Recommendations X.420 and T.330,

unanimously declares

(1)	that the abstract models of a Message Handling System are defined in section two;

(2)	that the configurations of a Message Handling System are defined in section three;

(3)	that naming, addressing, and routing within Message Handling Systems are defined in section four.

(4)	that the use of the Directory by Message Handling Systems is defined in section five.

(5)	that the OSI realization of a Message Handling System is specified in section six.

Table of Contents

Section One - Introduction

0.	Introduction

1.	Scope	1

2.	References

2.1	Open Systems Interconnection

2.2	Directory Systems	3

2.3	Message Handling Systems

3.	Definitions	4

3.1	Open Systems Interconnection

3.2	Directory Systems	6

3.3	Message Handling Systems

4.	Abbreviations

5.	Conventions

5.1	ASN.1

5.2	Grade

5.3	Terms

Section Two - Abstract Models

6.	Overview	8

7.	Functional Model

7.1	Primary Functional Objects

7.1.1	The Message Handling System

7.1.2	Users

7.1.3	Distribution Lists

7.2	Secondary Functional Objects

7.2.1	The Message Transfer System

7.2.2	User Agents

7.2.3	Message Stores

7.2.4	Access Units

7.3	Tertiary Functional Objects

7.3.1	Message Transfer Agents

7.4	Selected AU Types

7.4.1	Physical Delivery

7.4.2	Telematic

7.4.3	Telex

8.	Information Model

8.1	Messages

8.2	Probes

8.3	Reports

9.	Operational Model

9.1	Transmittal

9.2	Transmittal Roles

9.3	Transmittal Steps

9.3.1	Origination

9.3.2	Submission

9.3.3	Import

9.3.4	Transfer

9.3.5	Export

9.3.6	Delivery

9.3.7	Retrieva

9.3.8	Receipt

9.4	Transmittal Events

9.4.1	Splitting

9.4.2	Joining

9.4.3	Name Resolution

9.4.4	DL Expansion

9.4.5	Redirection

9.4.6	Conversion

9.4.7	Non-delivery

9.4.8	Non-affirmation

9.4.9	Affirmation

9.4.10	Routing

10.	Security Model

10.1	Security Policies

10.2	Security Services

10.2.1	Origin Authentication Security Services

10.2.2	Secure Access Management Security Service

10.2.3	Data Confidentiality Security Services

10.2.4	Data Integrity Security Services

10.2.5	Non-Repudiation Security Services

10.2.6	Message Security Labelling Security Service

10.2.7	Security Management Services

10.3	Security Elements

10.3.1	Authentication Security Elements

10.3.2	Secure Access Management Security Elements

10.3.3	Data Confidentiality Security Elements

10.3.4	Data Integrity Security Elements

10.3.5	Non-repudiation Security Elements

10.3.6	Security Label Security Elements

10.3.7	Security Management Security Elements

10.3.8	Double Enveloping Technique

Section Three - Configurations

11.	Overview	33

12.	Functional Configurations

12.1	Regarding the Directory

12.2	Regarding the Message Store

13.	Physical Configurations

13.1	Messaging Systems

13.1.1	Access Systems

13.1.2	Storage Systems

13.1.3	Access and Storage Systems

13.1.4	Transfer Systems

13.1.5	Access and Transfer Systems

13.1.6	Storage and Transfer Systems

13.1.7	Access, Storage, and Transfer Systems

13.2	Representative Configurations

13.2.1	Fully Centralized

13.2.2	Centralized Message Transfer and Storage

13.2.3	Centralized Message Transfer

13.2.4	Fully Distributed

14.	Organizational Configurations

14.1	Management Domains

14.1.1	Administration Management Domains

14.1.2	Private Management Domains

14.2	Representative Configurations

14.2.1	Fully Centralized

14.2.2	Directly Connected

14.2.3	Indirectly Connected

15.	The Global MHS

Section Four - Naming, Addressing, and Routing

16.	Overview

17.	Naming

17.1	Directory Names

17.2	O/R Names

18.	Addressing

18.1	Attribute Lists

18.2	Character Sets

18.3	Standard Attributes

18.3.1	Administration-domain-name

18.3.2	Common-name

18.3.3	Country-name

18.3.4	Extension-postal-O/R-address-components

18.3.5	Extension-physical-delivery-address-components

18.3.6	Local-postal-attributes

18.3.7	Network-address

18.3.8	Numeric-user-identifier

18.3.9	Organization-name

18.3.10	Organizational-unit-names

18.3.11	Physical-delivery-service-name

18.3.12	Personal-name

18.3.13	Physical-delivery-country-name

18.3.14	Physical-delivery-office-name

18.3.15	Physical-delivery-office-number

18.3.16	Physical-delivery-organization-name

18.3.17	Physical-delivery-personal-name

18.3.18	Post-office-box-address

18.3.19	Postal-code

18.3.20	Poste-restante-address

18.3.21	Private-domain-name

18.3.22	Street-address

18.3.23	Terminal-identifier

18.3.24	Terminal-type

18.3.25	Unformatted-postal-address

18.3.26	Unique-postal-name

18.4	Attribute List Equivalence

18.5	O/R Address Forms

18.5.1	Mnemonic O/R Address

18.5.2	Numeric O/R Address

18.5.3	Postal O/R Address

18.5.4	Terminal O/R Address

18.6	Conditional Attributes

19.	Routing

Section Five - Use of the Directory

20.	Overview

21.	Authentication

22.	Name Resolution

23.	DL Expansion

24.	Capability Assessment

Section Six - OSI Realization

25.	Overview

26.	Application Service Elements

26.1	The ASE Concept

26.2	Symmetric and Asymmetric ASEs

26.3	Message Handling ASEs

26.3.1	Message Transfer

26.3.2	Message Submission

26.3.3	Message Delivery

26.3.4	Message Retrieval

26.3.5	Message Administration

26.4	Supporting ASEs

26.4.1	Remote Operations

26.4.2	Reliable Transfer

26.4.3	Association Control

27.	Application Contexts

Annexes

A	Directory Object Classes and Attributes

A.1	Object Classes

A.1.1	MHS Distribution List

A.1.2	MHS Message Store

A.1.3	MHS Message Transfer Agent

A.1.4	MHS Organizational User

A.1.5	MHS Residential User

A.1.6	MHS User Agent

A.2	Attributes

A.2.1	MHS Deliverable Content Length

A.2.2	MHS Deliverable Content Types

A.2.3	MHS Deliverable EITs

A.2.4	MHS DL Members

A.2.5	MHS DL Submit Permissions

A.2.6	MHS Message Store

A.2.7	MHS O/R Addresses

A.2.8	MHS Preferred Delivery Methods

A.2.9	MHS Supported Automatic Actions

A.2.10	MHS Supported Content Types

A.2.11	MHS Supported Optional Attributes

A.3	Attribute Syntaxes

A.3.1	MHS DL Submit Permission

A.3.2	MHS O/R Address

A.3.3	MHS O/R Name

B	Reference Definition of Object Identifiers

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 MATTER | +- Introduction -+--------------------------------------------+ | X.400 | 8505-1 | Service and system overview | | X.402 | 8505-2 | Overall architecture | +- Various Aspects -------------------------------------------+ | X.403 | - | Conformance testing | | X.407 | 8883-2 | Abstract service definition conventions | | X.408 | - | Encoded information type conversion rules | +- Abstract Services -----------------------------------------+ | X.411 | 8883-1 | MTS Abstract Service definition and | | procedures for distributed operation | | X.413 | TBS-1 | MS Abstract Service definition | +- Protocols ----+--------------------------------------------+ | X.419 | 8505-2 | Protocol specifications | +- Interpersonal Messaging System ---------------------------+ | X.420 | 9065 | Interpersonal Messaging System | | T.330 | - | Telematic access to IPMS | +-------+--------+--------------------------------------------+

The Directory, the principal means for disseminating communication-related information among MHS components, is defined in the X.500-series Recommendations, as summarized in Table 2/X.402.

Table .T.:2/X.402 Specifications for Directories

+-------+--------+--------------------------------------+ | CCITT | ISO | SUBJECT MATTER | +- Model --------+---------------------------------------+ | X.200 | 7498 | OSI Reference Model | +-------+--------+---------------------------------------+ | X.500 | 9594-1 | Overview | | X.501 | 9594-2 | Models | | X.509 | 9594-8 | Authentication framework | | X.511 | 9594-3 | Abstract service definition | | X.518 | 9594-4 | Procedures for distributed operation | | X.519 | 9594-5 | Protocol specifications | | X.520 | 9594-6 | Selected attribute types | | X.521 | 9594-7 | Selected object classes | +-------+---------+--------------------------------------+

The architectural foundation for Message Handling is provided by still other Recommendations. The OSI Reference Model is defined in Recommendation X.200. The notation for specifying the data structures of abstract services and application protocols, ASN.1, and the associated encoding rules are defined in Recommendations X.208 and X.209. The means for establishing and releasing associations, the ACSE, is defined in Recommendations X.217 and X.227. The means for reliably conveying APDUs over associations, the RTSE, is defined in Recommendations X.218 and X.228. The means for making requests of other open systems, the ROSE, is defined in Recommendations X.219 and X.229.

The CCITT Recommendations and ISO International Standards foundational to Message Handling are summarized in Table 3/X.402.

Table .T.:3/X.402 Specifications for MHS Foundations

+-------+--------+--------------------------------------+ | CCITT | ISO | SUBJECT MATTER | +- Model --------+---------------------------------------+ | X.200 | 7498 | OSI Reference Model | +- ASN.1 --------+---------------------------------------+ | X.208 | 8824 | Abstract syntax notation | | X.209 | 8825 | Basic encoding rules | +- Association Control ---------------------------------+ | X.217 | 8649 | Service definition | | X.227 | 8650 | Protocol specification | +- Reliable Transfer -----------------------------------+ | X.218 | 9066/1 | Service definition | | X.228 | 9066/2 | Protocol specification | +- Remote Operations -----------------------------------+ | X.219 | 9072/1 | Service definition | | X.229 | 9072/2 | Protocol specification | +-------+---------+--------------------------------------+

This Recommendation is structured as follows. Section one is this introduction. Section two presents abstract models of Message Handling. Section three specifies how one can configure the MHS to satisfy any of a variety of functional, physical, and organizational requirements. Section four describes the naming and addressing of users and distribution lists and the routing of information objects to them. Section five describes the uses the MHS may make of the Directory. Section six describes how the MHS is realized by means of OSI. Annexes provide important supplemental information.

No requirements for conformance to this Recommendation are imposed.

2.	References

This Recommendation and others in the set cite the documents below.

2.1	Open Systems Interconnection

This Recommendation and others in the set cite the following OSI specifications:

X.200	Basic reference model.(see also ISO 7498).

X.208	Specification of abstract syntax notation one (ASN.1) (see also ISO 8824).

X.209	Specification of basic encoding rules for abstract syntax notation one (ASN.1) (see also ISO 8825).

X.217	Association control: Service definition (see also ISO 8649).

X.218	Reliable transfer: Model and service definition (see also ISO 9066-1).

X.219	Remote operations: Model, notation and service definition (see also ISO 9072-1).

X.227	Association control: Protocol specification (see also ISO 8650).

X.228	Reliable transfer: Protocol specification (see also ISO 9066-2).

X.229	Remote operations: Protocol specification (see also ISO 9072-2).

2.2 Directory Systems

This Recommendation and others in the set cite the following Directory System specifications: of concepts, models, and service.)

X.500	The directory Overview (see also ISO 9594-1).

X.501	The directory Models (see also ISO 9594-2).

X.509	The directory Authentication framework (see also ISO 9594-8).

X.511	The directory Abstract service definition (see also ISO 9594-3).

X.518	The directory Procedures for distributed operation (see also

ISO 9594-4).

X.519	The directory Protocol specifications (see also ISO 9495-5).

X.520	The directory Selected attribute types (see also ISO 9495-6).

X.521	The directory Selected object classes (see also ISO 9495-7).

2.3	Message Handling Systems

This Recommendation and others in the set cite the following Message Handling System specifications:

T.330	Telematic access to IPMS.

X.400	Message handling: Service and system overview (see also ISO 10021-1).

X.403	Message handling systems: Conformance testing.

X.407	Message handling systems: Abstract service definition conventions (see also ISO 10021-3).

X.408	Message handling systems: Encoded information type conversion rules.

X.411	Message handling systems: Message transfer system: Abstract service definition and procedures (see also ISO 10021-4).

X.413	Message handling systems: Message store: Abstract service definition

(see also ISO 1002105).

X.419	Message handling systems: Protocol specifications (see also

ISO 10021-6).

X.420	Message handling systems: Interpersonal messaging system (see also

ISO 10021-7).

3.	Definitions

For the purposes of this Recommendation and others in the set, the definitions below apply.

3.1	Open Systems Interconnection

This Recommendation and others in the set use the following terms defined in Recommendation X.200, as well as the names of the seven layers of the Reference Model:

a)	abstract syntax;

b)	application entity (.I.ab:AE;);

c)	application process;

d)	application protocol data unit (.I.ab:APDU;);

e)	application service element (.I.ab:ASE;);

f)	distributed information processing task;

g)	layer;

h)	open system;

i)	Open Systems Interconnection (.I.ab:OSI;);

j)	peer;

k)	presentation context;

l)	protocol;

m)	Reference Model;

n)	transfer syntax; and

o)	user element (.I.ab:UE;).

This Recommendation and others in the set use the following terms defined in Recommendations X.208 and X.209, as well as the names of ASN.1 data types and values:

a)	Abstract Syntax Notation One (.I.ab:ASN.1;);

b)	Basic Encoding Rules;

c)	explicit;

d)	export;

e)	implicit;

f)	import;

g)	macro;

h)	module;

i)	tag;

j)	type; and

k)	value.

This Recommendation and others in the set use the following terms defined in Recommendation X.217:

a)	application association; association;

b)	application context (.I.ab:AC;);

c)	Association Control Service Element (.I.ab:ACSE;);

d)	initiator; and

e)	responder.

This Recommendation and others in the set use the following terms defined in Recommendation X.218:

a)	Reliable Transfer (.I.ab:RT;); and

b)	Reliable Transfer Service Element (.I.ab:RTSE;).

This Recommendation and others in the set use the following terms defined in Recommendation X.219:

a)	argument;

b)	asynchronous;

c)	bind;

d)	parameter;

e)	remote error;

f)	remote operation;

g)	Remote Operations (.I.ab:RO;);

h)	Remote Operations Service Element (.I.ab:ROSE;);

i)	result;

j)	synchronous; and

k)	unbind.

3.2	Directory Systems

This Recommendation and others in the set use the following terms defined in the X.500-series Recommendations:

a)	attribute;

b)	certificate;

c)	certification authority;

d)	certification path;

e)	directory entry; entry;

f)	directory system agent (.I.ab:DSA;);

g)	Directory;

h)	hash function;

i)	name;

j)	object class;

k)	object;

l)	simple authentication; and

m)	strong authentication.

3.3	Message Handling Systems

For the purposes of this Recommendation and others in the set, the definitions indexed in annex G apply.

4.	Abbreviations

For the purposes of this Recommendation and others in the set, the abbreviations indexed in annex G apply.

5.	Conventions

This Recommendation uses the descriptive conventions identified below.

5.1	ASN.1

This Recommendation uses several ASN.1-based descriptive conventions in annexes A and C to define the Message Handling-specific information the Directory may hold. In particular, it uses the OBJECT-CLASS, ATTRIBUTE, and ATTRIBUTE-SYNTAX macros of Recommendation X.501 to define Message Handling-specific object classes, attributes, and attribute syntaxes.

ASN.1 appears both in annex A to aid the exposition, and again, largely redundantly, in annex C for reference. If differences are found between the two, a specification error is indicated.

Note that ASN.1 tags are implicit throughout the ASN.1 module that annex C defines; the module is definitive in that respect.

5.2	Grade

Whenever this Recommendation describes a class of data structure (e.g., O/R addresses) having components (e.g., attributes), each component is assigned one of the following .I.gl:grade;s:

a)	.I.gl:mandatory; (.I.ab:M;): A mandatory component shall be present in every instance of the class.

b)	.I.gl:optional; (.I.ab:O;): An optional component shall be present in an instance of the class at the discretion of the object (e.g., user) supplying that instance. There is no default value.

c)	.I.gl:defaultable; (.I.ab:D;): A defaultable component shall be present in an instance of the class at the discretion of the object (e.g., user) supplying that instance. In its absence a default value, specified by this Recommendation, applies.

d)	.I.gl:conditional; (.I.ab:C;): A conditional component shall be present in an instance of the class as dictated by this Recommendation.

5.3	Terms

Throughout the remainder of this Recommendation, terms are rendered in bold when defined, in italic when referenced prior to their definitions, without emphasis upon other occasions.

Terms that are proper nouns are capitalized, generic terms are not.