Implementing X.400 Backbones A Guide for Planners and Support Staff David Ferris Cemil Betanov Ferris Research information for planners and implementers of enterprise messaging Copyright ©1995 by Ferris Research, Inc. All rights reserved. Reproduction prohibited without permission. No part of this document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means—electronic, photocopying, mechanical, recording, known today or hereafter invented—without the prior written permission of Ferris Research. The material contained herein is based on information Ferris Research believes is reliable, but its accuracy and completeness cannot be guaranteed. No liability is assumed for the use of any materials presented herein, nor for any errors or ommisions which may remain. Copyright ©1995 by Ferris Research, Inc. All rights reserved. Reproduction prohibited without permission. For Jean and Nicholas For Rossana, Emile, and Adrian Table of Contents Sponsor Credits Preface iii How the Report is Organized iii Development Method iv Product Assessments iv Development Team vii David Ferris, Editor and Principal Investigator vii Cemil Betanov, Co-Author vii About Ferris Research viii Authors' Thanks ix Executive Summary xi Report Highlights xii Alternative Technologies xii Message Transfer System xii Directories xiii Gateways xiii APIs xiii Management xiii X.400 UAs xiv ADMDs xiv Other xv 1. Introduction 17 1.1 Messaging System Services 17 Fundamental Services 19 Message Preparation Services 19 Message Store Services 20 Transport Services 20 Directory Lookup Services 21 Message Status Services 22 Directory Support Services 23 Gateway Services 23 Automated Housekeeping Services 24 User Account Housekeeping Services 25 General Management Services 25 User Agent & API Services 25 User Agents 25 APIs 26 1.2 What's an X.400 Backbone?T 26 Evolution as Integrator of Non-X.400 Systems 27 Why Point-to-Point Gateways are Impractical 2828 The Backbone Approach 3030 Message Switches, or E-Mail Integration Sofiware 3131 Basic Backbone Features 3232 Backbone Requirements 3232 1.3 The Backbone as Vehicle for PC E-Mail Reliability 3333 Reasons for PC E-Mail Unreliability 3333 How an X.400 Backbone Can Improve Reliability 3434 1.4 Backbone Components 3535 Backbone Connecting Non-X.400 Systems 3535 E-Mail Systems Connecting to the Backbone 3636 Underlying Data Communications Links 3636 Where Messaging Services are Provided 3737 2. X.400 Technology Background, Part I 4141 2.1 Message Format 4141 The P1 Protocol 4141 The P2 Protocol 4141 The P22 Protocol 4343 The PO Protocol 4343 The FEDI Protocol/X.435 4343 Body Parts 4343 Delivery Notifications 4343 Receipt Notifications 4444 2.2 User Agent & Message Store 4545 Transit Via Message Store 4646 Transit Via Direct MTA Submission 4646 Access By Non-X.400 User .Agents 4747 2.3 Message Transfer Agent 4747 MTA-MTA Authentication 4848 Security by Limiting Correspondents 4949 2.4 ADMDs & PRMDs 4949 2.5 Addresses 5050 Mnemonic ORAddress 5050 X.400 Addresses and Routing 5252 X.400 Addresses Are Hierarchical 5252 Values Usually Lower Case 5252 Domain Defined Attributes (DDAs) 5353 2.6 File Transfer and Conversion 5454 Unspecified File Attributes 5454 Large Files 5454 Transfer Cost 5555 File Conversion 5555 2.7 Directory Services 5555 The X.500 Directory 5555 X.500 Architecture 5656 X.500 Problems 5757 Directory Synchronization Within An Organization 5858 Directory Propagation 6060 Copyright 1995 by Ferris Research, Inc. All rights reserved. Reproduction prohibited without permission. 2.8 Distribution Lists 60 Management Issues 60 Recommendations 61 2.9 More on Addresses 62 What The Problems Are 62 Absurdity of Including ADMD Names 62 A=Single Space 63 Organizations with Multiple ADMDs 63 ADMD Attribute in PRMD-PRMD Connections 64 Country Attribute and Multinational Organizations 64 Indigestible 0= and OU= Information 64 Address Format Recommendations 65 Yardstick: Internet Addresses 65 Industry Simplification Attempts Going Nowhere 65 Address Convention Recommendations 66 EMA's Standard Mailbox Recommendations 67 Auto Answer Mailbox 68 Directory Services Mailbox 68 Helpdesk Mailbox 68 3. X.400 Technology Background, Part II 69 3.1 Data Communications Links 69 Messaging Protocols 69 Transport Protocols 70 X.25 70 Asynchronous Protocol Specification 71 APS Relevance & Status 71 Summary 72 3.2 1984, 88, 92 Specifications 72 Differences Between 84 and 88 Versions 73 Connecting 1984 and 1988 Systems 73 3.3 X.API Association 74 Goal: Hide X.400 Complexity From Programmers 74 3.4 Connecting to An ADMD 75 X.25 75 Installation & Planning Effirts 75 Dialup Connections 76 3.5 Support for EDI 76 X.435 Basics 78 3.6 Security 78 US Government Restrictions 79 Interoperability 80 3.7 Connecting To Customers & Trading Partners 80 Alternatives to X400 Connections 80 X.400 External Connectivity Benefits 81 PRMD-PRMD Connection Benefits 82 PRMD-ADMD Connection Benefits 82 Making The Physical Connection 83 Internet As PRMD-PRMD Connection 83 X.400 Connectivity Shortcut: Service Provider's X.400 Gateway 83 SMTP/MIME and the Internet 86 SMTP/MIME As Backbone 86 Standards Definition Faster Than ISO 87 SMTP/MIME Advantages As Backbone 87 SMTP/MIME Disadvantages As Backbone 89 PC E-Mail Everywhere 90 Advantages Of PC E-Mail Everywhere 90 Disadvantages Of PC E-Mail Everywhere 91 4. Directory Services 93 4.1 What's a Directory? 93 System Directories 94 Messaging Directories 95 Employee Directory 95 Special-Purpose Directories 95 4.2 The Messaging Directory 95 What Information is Stored? 96 The Important Issues 96 4.3 Address Lookup 97 Lookup Tightly Integrated With Application 97 General-Purpose Directory Query 98 4.4 User Administration 99 Centralized vs. Distributed Administration 99 Role of Human Resource Database 101 Distributed Personnel c Network Management 101 Autonomous Divisions with own HR 101 International Organizations 101 Product Support for Centralized Administration 102 Administration-by-Mail 102 Initial Directory Load 102 Other Database Connections 102 4.5 External Access 103 Role of X.500 103 Proprietary Access Control for X.500 104 Access by Autonomous Divisions 104 4.6 MTA Routing 105 Routing Table Maintenance is a Major Scalability Obstacle 105 Bad Solution: Put Routing Information in Addresses 107 Bad Solution: Routing Hubs 108 Problems of Hub-and-Spoke Architectures 110 Good Solution: Directory-Based Routing 110 Advantages of Direct Routing 110 Occasions When Relaying Makes Sense 111 X.500 is Focus of Action 112 ISODE Consortium Approach 112 5. Directory Synchronization 115 5.1 Propagation vs. Synchronization 115 Name and Address Translation is Also Required 116 5.2 How Directory Synchronization Works 117 The Master Directory 117 The Synchronization Process 117 International and Cross-Division Synchronization 120 Directory Propagation 121 5.3 Product Solutions 122 Copyright ©1995 by Ferris Research, Inc. All rights reserved. Reproduction prohibited without permission. Avoid Building Your Own Directory Synchronization 122 Lotus/SoftSwitch's Directory Synchronization 123 How it Works 123 Strengths 124 Weaknesses 125 Retix' DX 125 5.4 Implementation Issues 126 Use Third Party Packages if You Can 126 Filtering & Security 126 Verification Tools. 127 Role of X.500 127 Synchronization Frequency 127 Multi-Tier Synchronization 127 Centralized Administration 128 Don't Confuse With Message Flow 128 6. Address Translation 129 6.1 Survey of Address Formats 129 BeyondMail, ON Technology's eMAII, Notework 129 cc:Mail 130 CompuServe 130 MCI Mail 130 Microsoft Mailfbr PC Networks 131 PROFS/OV 131 QuickMail 131 SMTP/Internet 132 X.400 132 6.2 Basic Translation Concepts 132 Naming Conventions Also Demand Translations 133 Inflexibility of Older Systems 134 Benefits of Name and Address Translation 134 Three Key Translation Requirements 135 How Address Translation Works 135 6.3 Table-Based Translation 135 6.4 Rules-Based Translation 136 Eg: Mapping X.400 Addresses to cc:Mail Addresses 136 Eg: Mapping cc:Mail Addresses to X.400 Addresses 137 .Fg: Mapping X.400 Addresses to SMTP/Internet 137 Eg: DDAs Used To Generate X.400 Addresses 138 Administrator-Selectable Rules 138 Administrator-Defined Rules 138 6.5 How Rules Apply 139 Centralized Translation Required 140 6.6 Autoregistration 142 6.7 Inline Addressing 142 6.8 Translation Problems 143 General 144 No Administrator-Selectable Translation Rules 144 Table-Based Translation Very Laborious to Maintain 144 External Mail Not Delivered 144 Sloppy Naming Conventions 144 Administrator-Selectable Translation Rules Inadequate 145 Duplicate Names 145 Non-Unique Translations 146 MTA Routing Confused by DDAs 146 Multi-Hop Name Translation 146 Co-Recipient Address Translation 147 Autoregistration and Inline Addressing 148 Cryptic Autoregistration Names and Addresses 148 Table Entries Proliferate 149 Multiple Addressesibr Same Person 149 Inline Addressing Easy to Get Wrong 149 Inline Addressing Creates Confusing Messages 149 7. File Transfer & Conversion 151 7.1 Viewers 151 7.2 How File Transfer Works 153 PC E-Mail File Transfer Is Messy 154 X.400 File Transfer Is Messier 154 Body Part 1A5Text/ASCII 155 Body Part Type 14 155 Body Part Type 15 155 File Transfer Body Part 156 7.3 Preserving File Attributes Across X.400 Gateways 156 From Non-X.400 to X.400 156 Tunneling 157 From X.400 to Non-X.400 158 7.4 Large Message Transfer Problems 158 Message Too Large For The System 158 System Breakdowns 159 Service Provider Charges 159 Everyone Gets Delayed 159 7.5 Desktop File Conversion 160 Possible Locations of File Conversion 160 Stand-Alone General-Purpose Conversion Packages 161 Built-In General-Purpose Conversion Packages 161 High End Graphics Conversion Packages 161 7.6 Backbone File Conversion 162 Strategic Advantages of Backbone Conversion 162 How Backbone-Based Conversion Works 163 What the Snags Are 163 Two Important Suggestions 163 7.7 Main Conversion Problems 164 Unknown File Format 164 Fonts Not Available 164 More Complex Documents 164 Basic Graphics 164 Advanced Graphics 165 Spread Sheet Macros 165 Crossing Platforms 165 Out of Date Converters 166 Features Not Translatable 166 OLE Files 167 8.