Network Working Group RARE WG-MSG Task Force 88 Request for Comments: 1616 May 1994 RARE Technical Report: 10 Category: Informational X.400(1988) for the Academic and Research Community in Europe A report by the RARE Task Force on X.400(1988) of the RARE Working Group on Mail & Messaging Status of this Memo This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited. 1. Abstract The European research and development community, as represented by the member research networks of RARE, has lead the deployment within the global R&D community of X.400 electronic messaging services, as specified in the international recommendations CCITT X.400(1984), for more than five years. As a result of providing such services to the European R&D users it has become clear that there is an existing and ever increasing demand from these users for new and enhanced electronic messaging services and product to be used to communicate within the R&D community but within commercial service providers and organisations as well. It is also clear that new services, such as Multimedia messaging and Secure messaging, and the resulting products promise dramatic benefits and opportunities, for not only the R&D community but also for the wider commercial, industrial and public communities, in terms of facilitating innovative ways of working and living which can only enhance the missions and goals of the respective communities. Not least the establishment of globally pervasive messaging services between all users, R&D and commercial, is facilitated by the early adoption of such advanced new services. An indication of the importance of such a messaging service can be appreciated if one considers that in many organizations (especially commercially based) messaging may be the only method to communicate between independent organizations due to security considerations and lower layer network differences. The Commission of European Communities (CEC) VALUE subprogram II has been established to support initiatives relating to the development and adaptation of R&D networks in member states. Amongst other RARE WG-MSG Task Force 88 [Page 1] RFC 1616 X.400(88) for European Academics and Research May 1994 initiatives the VALUE program supports X.400 initiatives in certain countries. VALUE support has so far been limited to X.400(1984) initiatives, as X.400(1984) has up until now been the dominating OSI services. However as X.400(1988) implementations have started to appear a VALUE funded study of the X.400(1988) aspects of messaging and their impact on the R&D community was felt necessary. This report is one of the results of that study. The report documents the results of a task force on X.400(1988) deployment of the RARE Mails and Messaging Work Group during the period from November 1992 until October 1993. Open reviews of the report have occurred in the RARE Mail and Messaging Work Group and within the IETF X.400ops Working Group. The scope of the report is limited to deployment of X.400(1988) services, and as such the report does not contain any recommendations on development and deployment of Internet RFC 822 / MIME/ PEM related (pilot) services. However, since the report shows that both X.400(1988) and RFC 822 / MIME / PEM will be developed and used within the European R&D community, such a pilot should also considered. Note: RFC 822 is also known as Internet STD 11. Circulation of this report is unlimited. Comments on this report may be sent to the e-mail distribution list: RFC 822: wg-msg@rare.nl X.400: S=wg-msg;O=rare;P=surf;A=400net;C=nl; Task Force Members: Claudio Allocchio (INFN), Harald T. Alvestrand (SINTEF), James C. I. Craigie (JNT), Urs Eppenberger (SWITCH), Frode Hernes (maXware), Jeroen Houttuin (RARE), Erik Huizer (SURFnet) - chairman, Steve Kille (ISODE Consortium), James A. (Jim) Romaguera (NetConsult). Editors: James A. (Jim) Romaguera & Erik Huizer The work of this Task Force has been funded by the Commission of European Communities (CEC) VALUE subprogram II, Stichting SURF and SURFnet bv. RARE WG-MSG Task Force 88 [Page 2] RFC 1616 X.400(88) for European Academics and Research May 1994 Table of Contents 1. Abstract 1 2. Management Summary 3 3. Framework for the report 6 4. Present situation of European Messaging 7 4.1. Messaging services 7 4.2. Requirements for messaging 8 4.2.1. User Oriented 9 4.2.2. Service provider viewpoint 10 4.3. Messaging capabilities 11 5. Possible solutions for providing globally pervasive messaging 12 5.1. PC LAN E-mail systems 13 5.2. RFC 822, MIME and PEM services 15 5.3. X.400 - 1984 and 1988 19 6. Migration to X.400(1988) 23 6.1. PC LAN E-mail systems 25 6.2. RFC 822, MIME and PEM services 25 6.3. X.400(1984) services 27 6.4. Mail-11 services 28 7. Benefits of migrating to X.400(1988) and the involved costs 28 8. Main Recommendations 33 9. Security Considerations 34 10. Reading List and Bibliography 35 11. Terminology 37 Appendix A - Elaboration on the main recommendations 38 Appendix B - A number of detailed guidelines. 40 Authors' Addresses 44 2. Management Summary This document reports the results of study of the X.400(1988) aspects of messaging and their impact on the R&D community. The study was funded by the CEC under VALUE Subprogram II and has been carried out by a task force on the RARE Mail Working Group. The document is targeted at technical decision makers as well as those who would fund activity in this area. The document presents the existing situation as regards the predominate messaging technologies within Europe. These are presented within the context of a number of large messaging communities that are using these technologies: - RFC 822, - X.400(1984), - Mail-11 and - PC LAN messaging RARE WG-MSG Task Force 88 [Page 3] RFC 1616 X.400(88) for European Academics and Research May 1994 Three major European communities are referenced: - Commercial service providers - R&D community - Commercial organisations using messaging services. The report states the following facts: - The resources, human or financial, to operate multiple wide area messaging services connecting together independent organisations are high. As such it is desirable to try and keep to a minimum the number of such services. This statement is true for the R&D community but is also highly likely to be valid for the general European industry. - There are two publicly available technological standards that can be used by open communities, such as the R&D community and public service providers: the X.400(1984 and 1988) recommendations and the Internet RFC 822 / MIME / PEM standards. - There is an established very large global user base of Internet RFC 822 and X.400(1984) messaging services. Both services have their own momentum within different parts of the user community, both are still developing and growing fast. The report concludes that X.400(1988) will be the preferred protocol for inter organizational connection for European industry and government and parts of the European R&D community. RFC 822 / MIME / PEM will be the preferred protocol suite for inter-organisational connection for the Internet community and, as products are already widely available, it is the preferred protocol for parts of the European R&D community. The goal of European pervasive messaging - incorporating Industry, Government and Academia - would be best accommodated and reached by the establishment of a single messaging service. However taking the above into account, this is not feasible, as X.400(84 and 88) and RFC 822( and MIME) based services will be around for a long time to come. To increase the functionality of Wide Area E-mail services there is a clear necessity to: - migrate RFC 822 services to a RFC 822 / MIME / PEM service. A MIME based service offers more functionality to the user than a plain RFC 822 service. - migrate existing X.400 services to a X.400(1988) service. RARE WG-MSG Task Force 88 [Page 4] RFC 1616 X.400(88) for European Academics and Research May 1994 Due to the lack of scalability of the X.400(1984) service in terms of extra functionality, it will become increasingly difficult to meet the needs of research users of existing X.400(1984) services unless an X.400(1988) service is put into place. - provide a transparent gateway between X.400(1988) and RFC 822/MIME/PEM. For the European R&D community it is essential to have a transparent gateway between the X.400(1988) service and the RFC 822 / MIME / PEM service, thus ensuring connectivity between these two services with a maximum functionality. Such a gateway is technically feasible and it is an essential part of an unified E-mail service. Without such a standardised gateway the overall E-mail service would deteriorate. The lack of open standards for the PC LAN messaging systems discourages their use as 'backbone' messaging technologies within open communities. However the products that these systems deliver to end users ensures that their already large share of the messaging market will continue to exist for some time. Thus it is also essential that strategies that allow these systems to be 'seamlessly' integrated within the global messaging community are put in place. Not least due to the indications that the main messaging vendors are developing X.400(1988) and RFC 822/MIME gateways, a strategy to link these systems together via X.400 and RFC 822 should be developed. The report concludes with a set of recommendations, the main one being the establishment of a X.400(1988) European pilot messaging service for the R&D community. This pilot should include the establishment of a transparent gateway service between X.400(1988) and RFC 822/MIME. The goal of a European pilot is to ensure the successful deployment of a European wide operational X.400(1988) service that is pervasive and meets the needs of users. By collecting together the issues related to the establishment of a European X.400(1988) service, this report acts as a focal point and stimulant for discussion on this topic within the R&D community. In the report a summary of the benefits and problems of each of the above messaging technologies within the context of achieving a global messaging service, of which the R&D community is one part, is presented. Further the document identifies issues, strategies and recommendations related to the migration and coexistence of these technologies within the scope of mainly the European R&D community but also in relation to other messaging communities. A cost / benefit analysis on the establishment of a European wide pilot X.400(1988) messaging service is also presented. Finally a reading list of references related to this subject has been compiled. RARE WG-MSG Task Force 88 [Page 5] RFC 1616 X.400(88) for European Academics and Research May 1994 The report does not include any recommendations on development and deployment of RFC 822 / MIME / PEM related (pilot) services, as these are outside of the scope of the Task Force. However, since the report shows that both X.400(1988) and RFC 822 / MIME / PEM will be developed and used within the European R&D community, such a pilot should also be considered. 3. Framework for the report With the belief that user demands for new messaging services such as Multimedia and Secure Messaging would develop, the RARE community (together with other communities; most notably the Internet Engineering Task Force (IETF)) has over the preceding years experimented in new messaging and related technologies. Experiments and pilots, have been performed in messaging services e.g., as recommended by CCITT X.400(1988) and Directory Services based upon the CCITT X.500(1988) recommendations. The results of such pilots and experiments indicate that it is now opportune to commence a pilot X.400(1988) messaging service for the European R&D community. The major goals of the pilot being, to - establish a large scale European wide pilot messaging service based on X.400(1988). - collaborate with and facilitate the commencement of similar pilot services within diverse communities; both R&D and non- R&D (e.g., commercial ADMDs and PRMDs, etc.); both European and non-European (e.g., North American , Asian, etc.). - encourage and assist the development and deployment of a wide variety of commercial and public domain X.400(1988) messaging products that meet the user's needs, for instance X.400(1988) products such as User Agents (UAs), Message Stores (MSs), Message Transfer Agents (MTAs) and gateways between X.400(1988) services and other widespread messaging services i.e., RFC 822, Mail-11 and proprietary. - prove that such a service and products efficiently meets the existing and expected demands for new messaging services by European R&D users. And as such determine the steps for a European deployment of an operational X.400(1988) messaging service. - determine the needed steps to facilitate migration for the existing operational R&D X.400(1984) based messaging service, as represented by the R&D MHS service (the former COSINE MHS), RFC 822 / MIME / PEM based messaging services and the RARE WG-MSG Task Force 88 [Page 6] RFC 1616 X.400(88) for European Academics and Research May 1994 HEPnet / SPAN Mail-11 based messaging service to an operational X.400(1988) messaging service. It is self evident that during such migrations, transition steps must be included that allow a period of coexistence, at the highest possible service level, between X.400(1988), X.400(1984), RFC 822 / MIME and HEPnet / SPAN Mail-11 services. - determine the needed steps that allow proprietary messaging systems, that are widely deployed within the European R&D community to be integrated at as high as possible service level, by an X.400(1988) infrastructure. This report identifies the issues involved in such a pilot service. It is not a concrete proposal for such a project but the report discusses advantages and disadvantages, costs and enefits and migration issues for deploying a X.400(1988) service. As such it is a discussion and feasibility paper on the creation of a large scale European wide pilot X.400(1988) messaging service for the European R&D community. 4. Present situation of European Messaging 4.1. Messaging services Electronic messaging within Europe can be viewed as a number of messaging services communities. Three important communities comprise, - Commercial e-mail networks, - Research e-mail networks and - PC LAN messaging systems. Commercial e-mail networks are classified as either ADMDs or PRMDs. ADMDs and PRMDs are operating in nearly every European country. - ADMD services (or public commercial e-mail services) are provided by over 50 service providers which have interconnected using the X.400(1984) protocols. The topology between these ADMDs, although not yet 'mesh', can be stated as progressing quite rapidly to this optimum goal. However there is still a way to go before ADMDs provide full European connectivity. - PRMDs (or private commercial e-mail service providers) have interconnected to ADMDs and other PRMDs predominantly using the X.400(1984) protocols but also with proprietary protocols. RARE WG-MSG Task Force 88 [Page 7] RFC 1616 X.400(88) for European Academics and Research May 1994 Research networks are providing messaging services in every European country. These R&D service providers are operated as either ADMDs or PRMDs and are using both X.400(1984) protocols and Internet RFC 822 protocols to connect to each other. Moreover, there are also large R&D communities (i.e., HEPnet and SPAN) using proprietary protocols (i.e., DECnet Phase IV and Mail-11) as their main messaging systems. The DECnet IV based communities are now migrating to DECnet Phase V (OSI connectionless protocol stack), which provides X.400(1988) (plus X.400(1984)) as a major messaging system. In general, all these services are totally interconnected. As such it is a statement of fact that there exists within the European R&D community, two parallel interconnected messaging infrastructures based upon X.400(1984) and RFC 822. However interconnections between the R&D messaging community and the majority of the European commercial service providers use the X.400(1984) protocols. It is also clear that the commercial world mostly makes inter- organizational messaging interconnections using the X.400(1984) protocols. And also that the commercial messaging world is not as totally interconnected as the R&D messaging community. Finally, for a number of commercial and public organisations there is often a mandatory requirement to use X.400 for messaging interconnections. The usage of PC LAN messaging systems is increasing very rapidly within the academic and commercial communities. In general, PC LAN messaging services within both communities do not use X.400(1984) or RFC 822 messaging systems but systems based upon proprietary protocols. The PC LAN messaging systems can be considered more as 'Islands of Messaging' that gateway to the commercial and R&D messaging services by using X.400(1984) or RFC 822 gateways. PC LAN messaging systems within commercial organisations connect to commercial service providers also via proprietary protocols. The PC LAN messaging services, although probably comprising the largest number of users, are in general poorly integrated with the global messaging service (The Dutch, UK and Italian academic communities confirm that there appears to be many such 'Islands' of PC LAN messaging systems within their networks.). 4.2. Requirements for messaging Experience with existing global e-mail services has proven that with the increased use of messaging, there follows an awareness of extra requirements for related services. These requirements can be classified into 'User based Requirements' and 'Service Provider based Requirements' to either support, or exploit, high quality messaging services. These requirements are elaborated upon within this chapter. RARE WG-MSG Task Force 88 [Page 8] RFC 1616 X.400(88) for European Academics and Research May 1994 4.2.1. User Oriented The only thing a user requires is an easy to use, well integrated, user interface to electronic mail. Usually the user does not care what protocol is used. However there are certain inherent requirements to the functionality that can be identified as user requirements. The main user requirements identified are: - Distribution Lists (DLs) A widely perceived omission from the X.400(1984) recommendations was the lack of support of DLs. Distribution lists allow users to enlist themselves onto electronic mail expander lists (distribution lists). A message to such a distribution list will automatically, and without significant delay, be sent on to anyone whose electronic mail address is on that list. Such a list can be a public list, that is meant for discussions on a specific subject, much like a sort of "magazine". However the list can also be a "closed" list, containing only a selected set of people who need to communicate privately, e.g., a project-team. - Multinational language and Multimedia support European users have for many years been frustrated in their inability to use their national character sets when communicating using messaging systems. The problems within e-mail systems that were causing this character set frustration are at their base the same problem that would get in the way of Multimedia messaging like: - lack of binary data support - lack of standardised encoding schema's - definition of multiple body-parts The enormous potential of Multimedia systems and services (especially within the commercial community as evidenced by the enormous press publicity and mega-mergers positioning companies to exploit this technology but also within the government spheres i.e., the U.S.A. Government's 'Information Superhighway' initiative) has acted as a spur to make rapid progress in solving the problems in this area. - White pages Directory Service A white pages directory service provides a unique but very basic and important service; a way to store and find information about people and resources that is analogous to a telephone service's paper based directory i.e., White Pages. User's E-mail addresses RARE WG-MSG Task Force 88 [Page 9] RFC 1616 X.400(88) for European Academics and Research May 1994 can be stored for subsequent retrieval by E-mail systems. - EDI EDI today is not extensively used within the academic environment. However there is a distinct potential within the academic community to reduce costs and improve services with EDI. Potential EDI uses could be, - EDI between universities - EDI between universities and government - EDI between universities and lower level educational institutions (e.g., student records) - Commercial EDI using the Internet as an infrastructure. The significance of maintaining end to end integrity (especially security aspects) of the EDI messages mandates that no gateways should be used between originator and recipient. - Support of Security services E-mail as it is currently used is far from secure. To allow for serious usage of E-mail security issues need to be addressed, like: - integrity; making sure that the message is transferred intact, without any changes or additions. - encryption; making sure the message content is only decipherable by the intended recipient. - authentication; making sure that the originator and/or recipient are authenticated. 4.2.2. Service provider viewpoint The task force believes the following points as being the most significant service provider requirements: - Network Management This area is still very new, in terms of offering standardised protocols, services and products for management. However a minimum 'goal' is to provide for central management functions that will allow providers to offer a better quality of service. There is presently ongoing work within the IETF Working Group MADMAN to define SNMP monitoring and managing of E-mail systems, gateways and X.500 directory systems. A number of management areas that need to be worked upon include: QOS, Service Level Agreements (SLAs), Multiple system queue management, Accounting, Routing Co- RARE WG-MSG Task Force 88 [Page 10] RFC 1616 X.400(88) for European Academics and Research May 1994 ordination and Message Tracing. - Support of MTA routing Dynamic routing from MTA to MTA, relieves the necessity to maintain large routing tables, especially within a large PRMD, or community of PRMDs (like the R&D MHS community). - Address mapping between RFC 822 and X.400 The widespread use of X.500 or DNS for mapping, allows a reduction of manpower for centrally co-ordinating globally consistent X.400-to-RFC-822 mapping tables and distributes the responsibility for updating the mapping rules. This should allow mapping rules to change when needed and to be available immediately. - UA capabilities registration The use of the directory to register UA capabilities for X.400(1988), X.400(1984) and RFC 822 / MIME / PEM systems is a very desirable benefit for users in terms of speeding the deployment of new messaging services (e.g., Multimedia Messaging). 4.3. Messaging capabilities Due to the problems of gatewaying within a multi-protocol messaging environment, the great majority of R&D E-mail users are reduced to using only InterPersonal Messaging (IPM) services based upon the exchange of message body parts using CCITT character set IA5 (US ASCII). Within the R&D community recent work to meet user requirements for non ASCII messaging services - as documented above - has resulted in enhancements to the messaging services based upon RFC 822 protocols. The enhancements provide Multimedia support via the Multipurpose Internet Mail Extensions (MIME) and the prospect in the very near future of secure messaging via Privacy Enhanced Mail (PEM). Deployment of the MIME enhanced RFC 822 based services, via distribution of software and the setting up of the needed organisational structures, has commenced. The PEM enhancements are in a large scale pilot phase e.g., VALUE PASSWORD project. In the case of X.400(1984) the usage of non ASCII body parts is mostly effected by bilateral agreement between recipient and originator, through use of body part 14. In practice this restricts the exchange of non ASCII body parts to those cases where the recipient and the originator use the same bilateral agreement or else the originator includes an ASCII message explaining the included RARE WG-MSG Task Force 88 [Page 11] RFC 1616 X.400(88) for European Academics and Research May 1994 content type. Besides IPM there is a growing usage of EDI on top of X.400(1984). With the above X.400(1984) deficiencies in mind, X.400(1988) has been specified by the CCITT / ISO to meet new user demands. X.400(1988) provides support for various different body parts, enhanced security features, international character set support capabilities and support of X.500 Directory Services. Due to the technological potential of these standards to satisfy user needs for new messaging services, the R&D community has been experimenting and piloting X.400(1988) and X.500(1988) services. As there is a strong dependency of X.400(1988) messaging upon X.500(1988) directory services, the necessary precondition to supply these user demands is a deployed and operational X.500(1988) directory service. Piloting and deployment of the X.500(1988) directory service within the R&D community has been successfully initiated and co-ordinated by the COSINE and the VALUE PARADISE projects. Similarly, secure messaging has been addressed by the VALUE PASSWORD project and the RARE and IETF communities. Work to solve problems related to directory support of X.400(1988) messaging has been pursued within the IETF and RARE. The relevant RARE and IETF work groups (e.g., RARE WG-MSG, IETF MHS-DS, etc.) have also worked to produce any needed enhancements to the base X.400(1988) and X.500(1988) standards. Last but not least it should not be overlooked that X.400(1988), as compared to X.400(1984), provides a comprehensive basis for gatewaying to and from RFC 822 / MIME / PEM and PC LAN messaging services. To that respect the IETF has defined standards for gatewaying Multimedia mail between RFC 822 / MIME / PEM and X.400(1988). As RFC 822 / MIME / PEM is now being deployed on the Internet, deployment of X.400(1988) services is needed to assure multimedia and secure messaging connectivity for the European R&D community. 5. Possible solutions for providing globally pervasive messaging As can be now seen, a correlation of the present situation to the requirements of the user, shows that the current messaging services do not match the needs of users. To try to meet these needs a number of developments within various messaging technology areas are occurring. The following messaging technological areas, due to the present installed user base within the R&D community, are considered relevant: - PC LAN E-mail systems such as Lotus cc:Mail, Microsoft Mail and Novell MHS - RFC 822 / MIME / PEM E-mail services - X.400(1988) messaging services RARE WG-MSG Task Force 88 [Page 12] RFC 1616 X.400(88) for European Academics and Research May 1994 Ongoing developments within each of the above technological areas provide new messaging options for the R&D community. The ability of each technological area to provide solutions for user and service provider requirements is summarised within this chapter. 5.1. PC LAN E-mail systems Currently the usage of PC LAN E-mail systems is mostly for internal communication within an organisation. External connections, if present at all, to public service providers or other organisations is mostly through gateways to X.400(1984) or RFC 822. The use of a PC LAN E-mail system in terms of an infrastructure for interconnecting E-mail systems of different hues is not common within the Research community. Recent experience, from amongst others the Dutch Research network - SURFnet - [14] and the Norwegian Directorate for Public Management - Statskonsult - [18], has shown that a number of problems (i.e., limited functionality, high operational management cost, etc.) can be expected should these PC LAN E-mail systems be used as an E- mail infrastructure. (The use of native X.400 protocols for PC LAN E-mail systems would avoid the usage of gateways and would thus alleviate many of these problems.) A summary of those problems and some relevant issues follows: - Interconnecting heterogeneous PC LAN messaging systems One very distinct benefit for E-mail users of all hues is the potential to integrate heterogeneous PC LAN messaging systems with a minimum loss of service (e.g., multimedia services) by connecting them via X.400(1988) (or RFC 822/MIME/SMTP). X.400(1988) is already being used, or under active development, for connecting together PC LAN messaging systems in a number of environments (e.g., Apple Macintoshes, DEC, Microsoft, Lotus, etc.). This tendency to gateway PC LAN messaging systems via X.400(1988) will increase and is one of the benefits that X.400(1988) brings to global multiprotocol messaging. - Multimedia and binary data support The benefit of E-mail systems using these PC LAN systems is that the user interfaces are usually well integrated in the users standard working environment. Using a proprietary protocol these systems allow not only text (ASCII) but also binary, word processor, video, audio and other types of files to be transported. To reap the benefits of this multimedia / binary data transfer it would normally require that the same type of gateway is used by sender and receiver. Transporting these same files to another type of PC LAN E-mail system is not possible through the RARE WG-MSG Task Force 88 [Page 13] RFC 1616 X.400(88) for European Academics and Research May 1994 current gateways without some information loss. In effect PC LAN E-mail system's X.400 (or RFC 822) gateways from different vendors perform acceptably only for text body parts. True heterogeneous multimedia PC LAN messaging needs gateways to X.400(1988)'s service. - Application Programming Interfaces To help solve the problem of portability for Mail Enabled Applications Microsoft, Lotus, Novell, XAPIA and X/OPEN have been working on a number of standards for the Application Interface to mail transport protocols (i.e., Mail Application Programming Interface - MAPI, Vendor Independent Messaging - VIM, Common Mail Calls - CMC). These efforts are structured independent of the existing 'Wide-Area' or inter organisational E-mail protocols of X.400(1984) and RFC 822. However the MAPI, VIM and CMC efforts, due to their proposers (respectively Microsoft, Lotus and X/OPEN), do look like they will provide the stimulant to various software developers to develop more portable applications plus allow the rich functionality of X.400(1988) to be accessed by these applications thus reducing the need for gatewaying to X.400(1988). - Security As the PC LAN E-mail systems require gateways for connectivity, they pose a problem with regard to encrypted messages. Gatewaying of secure messages is normally not possible. The gatewaying of secure messages is a general problem of gatewaying from one mail system to any other system and is not specific to PC LAN E-mail systems. - Directory Services To date mostly proprietary directory services have been deployed that do not match the needs of the users in terms of access controls for data, distributed and decentralised across organisations. X.500 based services promise solutions to such needs. As a result various suppliers have announced support of X.500 directory services for their E-mail products. However, should these interfaces be delayed then support of an inter organisational 'White Pages' services requires either, - directory information exchange products (i.e., directory gateways) deployed between a proprietary system and an X.500 directory system RARE WG-MSG Task Force 88 [Page 14] RFC 1616 X.400(88) for European Academics and Research May 1994 - gateways between de-facto market based proprietary standards, such as Retix Directory Exchange (DX) or Soft*switch's Directory Synchronisation (DS), and X.500 protocols - duplicated directories i.e., one proprietary and one X.500 need to be operated. It should be stressed that gatewaying mechanisms and products are often problematic due to the lack of an open standard on the proprietary messaging system and or directory system. (As an aside it is thus essential to establish an operational X.500 infrastructure, including E-mail user interfaces that can transparently access this Directory Service, as soon as possible.) 5.2. RFC 822, MIME and PEM services RFC 822 messaging services are widely deployed within the R&D community. There is ongoing work to extend RFC 822 to meet user requirements. Some of these extensions are elaborated upon within this chapter. - Distribution lists RFC 822 allows for the usage of DLs. Management of DLs is not (yet) standardised. - RFC 822 multimedia messaging via MIME With the arrival of MIME, the RFC 822 service has an additional protocol standard that addresses Multimedia messaging very comprehensively. In terms of user needs, MIME now allows messaging body parts to comprise multinational character sets and binary data. Multi-body part messages are also supported. One of MIME's real strengths, in terms of deployment within the existing RFC 822 service, is that it achieves its goals by overlaying its services over the existing RFC 822 service and thus mandating no changes to the in place RFC 822 infrastructure. This greatly simplifies the MIME deployment. - RFC 822 secure messaging via PEM Just as MIME has brought multimedia messaging to RFC 822 services, Privacy Enhanced Mail (PEM) is bringing secure messaging to RFC 822 services. PEM also has used the same approach as MIME to deploy secure messaging within RFC 822 services; overlay PEM services over the existing RFC 822 services without requiring changes to the RFC 822 infrastructure. PEM brings confidentiality RARE WG-MSG Task Force 88 [Page 15] RFC 1616 X.400(88) for European Academics and Research May 1994 and integrity of messages to RFC 822 users. However a number of problems with PEM, and X.400(1988) as well, still need to be solved before secure messaging can be considered to be an operational service. These problems are independent of the secure messaging protocol (i.e., PEM or X.400(1988)) and deal mainly with distribution of secret keys to the end users. There is very active work going on within the IETF to solve these problems. - MIME and PEM There are still problems for messages that are simultaneously a multimedia message, as per MIME, and a secure message, as per PEM. A PEM encoded MIME message does not allow gatewaying to other messaging environments and therefore does not allow any of the features inherent within MIME to be exploited along the message path. A MIME message that contains PEM encoded body parts can be gatewayed but the integrity of the entire message is then not guaranteed. This is a real deficiency of both existing approaches as it is essential that users are able to simultaneously use multimedia and secure messaging. However, once again, the IETF is working very hard on solving these problems and solutions can be expected, although the solution of the gatewaying of PEM messages to other E-mail systems is still unclear. - Dynamic and distributed messaging routing via the Domain Name System (DNS) RFC 822 messaging benefits greatly by having a dynamic and distributed mechanism to assist in message routing i.e., Domain Name System (DNS). With the support of the DNS, RFC 822 MTAs are able to directly route to other RFC 822 MTAs and thus deliver messages with a minimum of delay. In practice mail often still traverses multiple RFC 822 MTAs for a number of reasons e.g., Mail Hubs provided for users who turn their machine off when they go home, Firewall Hubs for security reasons, etc. However it is commonly accepted that between RFC 822 mail hubs the delivery of messages is very fast. Typically resolution of routing decisions occurs in less than one minute and very often within seconds. In general the DNS service is a very valuable service that functions well in practice. - Support for Character sets Together with the MIME specification for content types, an extension for RFC 822 headers was defined that allows for usage of multiple character sets in names, subject etc. in RFC 822 headers [9]. This allows (European) users to use their preferred character set to support their language not only in the contents of a RARE WG-MSG Task Force 88 [Page 16] RFC 1616 X.400(88) for European Academics and Research May 1994 message but also in the headers. - MIME capable gateways It is clear that to provide a seamless service to all users regardless of whether they are using RFC 822 or X.400 services, a widely available set of well run and standardised RFC 822 to X.400 gateways must be in place. For InterPersonal Messaging (IPM) based on US ASCII there are already a large number of such standardised (i.e., X.400-to-RFC 822) gateways deployed. To ensure seamless gatewaying between MIME and X.400 multimedia users, these existing text based gateways must be either upgraded to or replaced with multimedia messaging gateways. A number of proposed Internet standards to solve these problems, for both X.400(1984) and X.400(1988) and generated within the MIMEMHS work group of the IETF, have been completed [4]. - Access to fax, teletex, telex or physical delivery For the moment, there is no standardised way for RFC 822 users to access gateways to the above services except by indirect access to X.400(1988) systems (i.e., concatenated gateways of RFC 822 to X.400(1988) and then onwards to the appropriate X.400(1988) Access Unit). Although even this indirect method would require some further work on standardising mappings between RFC 822 addresses and X.400(1992)'s X.121 addresses. As well some experiments within the RFC 822 world are occurring on routing fax messages. - Operational support Generally, RFC 822 messaging services are delivered on a 'best effort' basis and thus service level agreements requesting stringent response times to operational problems or guaranteed delivery times for messages are difficult to agree. This phenomena might be a result of the distribution and delegation of authority to organisations updating the RFC 822 MTA's routing mechanism i.e., DNS. As a result it makes it hard to reach a 'one stop shopping' agreement for RFC 822 messaging services. - Notifications The RFC 822 service provides a minimum amount of base protocol support for messaging users. It could be argued that the RFC 822 protocol is simplified by this choice and thus software that implements the standard need be smaller in size and easier to build. However some features e.g., delivery & receipt notifications and UA capabilities registration, would be commonly accepted as being desirable from a user standpoint and thus RARE WG-MSG Task Force 88 [Page 17] RFC 1616 X.400(88) for European Academics and Research May 1994 desirable extensions to RFC 822. Some operational problems relating to reliability could be minimised by technology that has a standardised support for positive and negative notifications of messages. RFC 822, as compared to X.400, technology does not yet support positive notifications (although there is work starting within the IETF to extend RFC 822 to support delivery notifications). However within RFC 821 transport system (i.e., SMTP) there are standardised negative notifications that work well. Alternatively X.400 technology, deployed over TCP/IP (using STD 35, RFC 1006), may help to address the lack of adequate service quality - notification support - when using E-mail within the Internet. - Portability of RFC 822 products There are only a few mailbox formats in general use by RFC 822 software, one being the 'bin/mail' format and the other 'MH' format. This 'standard' mailbox format is a definite benefit for RFC 822 users as it allows them to change RFC 822 UAs (e.g., upgrading to MIME RFC 822 UAs) whilst not compromising or converting their existing archived mail, which may comprise 1000s of archived messages. - System support for RFC 822 products Normally, RFC 822 MTAs and UAs come pre-installed on UNIX workstations. As a result, users are spared the effort of installing RFC 822 MTA software. If for some reason, a user or mail administrator should wish to install a different MTA or UA to the pre-installed system, there exists a large number of easily available (i.e., via widespread distribution amongst many FTP and other information servers) public domain RFC 822 MTAs and UAs. Both of the above points encourages the spread and eases the installation of software for the RFC 822 messaging service and in many ways explains the size and importance of the installed base of RFC 822 systems. To illustrate the extent of RFC 822 / MIME products, a non-comprehensive list of available MIME enhanced RFC 822 products follows; ELM 2.4, MH 6.8, Sun Mailtool, HP Mpower Desktop, Lotus cc:Mail (unconfirmed), Zcode Zmail, Frontier Super-TCP for Windows, PMDF (VAX VMS), Pine, C-Client (library routines), Metamail (viewer only), Andrew-MIME gateway. - UA capability registration The IETF MHS-DS working group has defined how X.400 and RFC 822 User Agent capabilities can be stored in X.500 directory services. This work is still ongoing. RARE WG-MSG Task Force 88 [Page 18] RFC 1616 X.400(88) for European Academics and Research May 1994 5.3. X.400 - 1984 and 1988 X.400(1988) substantially upgrades and enhances the X.400(1984) standards. A number of new functions have been incorporated within X.400(1988). A description of the most important features of X.400 - 1984 and 1988 - follows. - Notifications X.400(1984) provides four notifications - positive and negative delivery notifications and positive and negative receipt notifications. These notifications allow users to ensure successful message delivery or that the message was read. The delivery notifications are also used by service operators in their fault escalation procedures. - Binary Data Transfer X.400(1984) allows binary data transfer to be transported without the necessity of character encoding. The ability to transfer files of whatever type is a valuable end user service. As well the lack of any necessary character encoding allows users to utilise the received data without needing any character decoding software. - Multiple Body Parts The ability to send multiple body parts within one message gives the user the ability to send multiple logical components within one message. This is a natural mechanism for users as it mirrors the real life situation of being able to send within one message, a letter, a word processor file, a spreadsheet file, etc. - Feature rich messaging model The features of X.400 are very rich. This provides benefits for users as vendors are able to provide applications that can utilise these extensive features in an interoperable manner due to the standardisation of the features within X.400. - Clear messaging model X.400(1984), as one of its most wide reaching achievements, has popularised within the market a consistent and clear model to describe message handling systems. The decomposition of a message handling system into UAs, MSs, MTAs, MTS - ADMDs and PRMDs and Access Units / Gateways has proved to be an extremely useful tool for users and vendors to und