Network Working Group U. Eppenberger Request for Comments: 1465 SWITCH May 1993 Routing Coordination for X.400 MHS Services Within a Multi Protocol / Multi Network Environment Table Format V3 for Static Routing Status of this Memo This memo defines an Experimental Protocol for the Internet community. Discussion and suggestions for improvement are requested. 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. 1. Introduction The usage of the X.400 Message Handling System (MHS) is growing rapidly, especially in the commercial world but much interest can also be found in the academic and research community. New networks and new addresses come into use each and every day. The underlying technology for different X.400 networks can vary depending on the transport network and the X.400 MHS implementations used. As a large number of X.400 implementations now support multiple stacks, this offers the chance of implementing a world wide message handling service using the same electronic mail standard and, therefore, without the need of gateways with service reduction and without the restriction to a single common transport network. This, however, leads to several problems for the MHS manager, two of which are: - Where do I route new X.400 addresses and - How do I connect to a MHS domain that uses an underlying technology that I do not support. This document proposes short term solutions to these problems. It proposes a strategy for maintaining and distributing routing information and shows how messages can travel over different networks by using multi stack MTAs as relays. Document formats and coordination procedures bridge the gap until an X.500 directory service is ready to store the needed connectivity and routing information. The format has been designed to allow the information to be stored in an X.500 directory service while managers without directory service access may still use a table based approach. The routing structure proposed can be applied to a global MHS service Eppenberger [Page 1] RFC 1465 Routing Coordination for X.400 Services May 1993 but may also be used at a national level or even within an organisation. Many experts from IETF X.400-Operations Group and RARE Working Group 1 on Message Handling Systems have read drafts of this document and contributed ideas and solutions. I would especially like to thank Harald Alvestrand, Erik Huizer, Marko Kaittola, Allan Cargille and Paul-Andre Pays. This is the third version of a table format. The first one was in use within COSINE-MHS for about two years. A second version with major enhancements was then proposed which has been in use for the past year. The third version will probably be the last one before it will be possible to switch to dynamic, directory service based routing. 2. Terminology MHS community One or more MHS domains form an MHS community. Mail exchange between these MHS domains is defined by the coordination procedures within this document. Examples of such communities are the Global Open MHS service GO-MHS and the COSINE-MHS service. MHS domain One or more MHS subtrees form an MHS domain. This is a purely administrative grouping of MHS subtrees. It is helpful, if someone is responsible for several MHS subtrees, to refer to an MHS domain instead of listing all the subtrees. MHS subtree An MHS subtree consists of the total of the mailboxes addressable within a subtree of the X.400 OR address space. Example: O=SWITCH; P=SWITCH; A=ARCOM; C=CH; MHS domain of SWITCH in Switzerland, consisting of all mailboxes with O=SWITCH; P=SWITCH; A=ARCOM; C=CH; in the OR address. RELAY-MTA An X.400 MTA serving one or several MHS domains. Note that the term WEP -Well Known Entry Point- has been used since the early X.400ies (1987/88) until now, giving the wrong impression of a Eppenberger [Page 2] RFC 1465 Routing Coordination for X.400 Services May 1993 single entry point (and therefore a single point of failure). This document proposes to use the term RELAY-MTA, reflecting more clearly the functionality of the MTA. COSINE-MHS The COSINE-MHS community is mainly formed by European X.400 service providers from the academic and research area, each of which is a member of RARE. The COSINE-MHS community is used in the annex as an example for the usage of this document in a multinational environment. 3. Requirements X.400 MTAs can communicate using different transport and network protocol stacks. For this document the stacks used in a WAN environment need to be considered: Stack 1 Stack 2 Stack 3 Stack 4 Transport Layer 4 TP0 TP4 RFC1006 TP0 Networkservice 1-3 X.25 CLNS TCP/IP CONS A common protocol stack is not the only requirement to enable communication between two MTAs. The networks to which the MTAs belong need to be interconnected. Some well known networks are listed together with the stacks they use. Network Stack Abbreviation Public Switched Packet Data Networks 1 Public-X.25 International X.25 Infrastructure EMPB 1,4 EMPB-X.25 US and European connectionless pilot 2 Int-CLNS Internet 2,3 Internet Note that several stacks may be supported over a single network. However communication between MTAs is only possible if the MTAs share at least a common stack AND a common network. Unlike SMTP/TCP/IP systems, there is no directory service available which would allow an MTA to look up the next MTA to which it should submit a message. Routing within X.400 will continue to be table based until a solution using X.500 directory services is available. Furthermore it is not generally allowed to connect to any MTA even on the same network without being registered on the destination MTA. These restrictions require a large coordination effort and carefully configured and updated systems. Eppenberger [Page 3] RFC 1465 Routing Coordination for X.400 Services May 1993 4. Outline of the proposal This proposal offers a solution for describing information about X.400 message routing within an MHS community in RELAY-MTA and DOMAIN documents. Basic information on the MHS community is documented in the corresponding COMMUNITY document. All contact persons and RELAY-MTA administrators can be found in PERSON documents. A future X.500 based solution may need extended information to overcome still unsolved problems like optimal routing or traffic optimization for messages with multiple recipients. The information collected for the intermediate solution however is very basic. All established coordination procedures will help and even speed up the future introduction of an X.500 based solution. 4.1 The COMMUNITY document For each MHS community there exists one single COMMUNITY document containing basic information. First the contact information for the central coordination point can be found together with the addresses for the file server where all the documents are stored. It also lists network names and stacks to be used in the RELAY-MTA and DOMAIN documents. An MHS community must agree on its own set of mandatory and optional networks and stacks. 4.2 The RELAY-MTA document Every MHS domain in the community may designate one or more MTAs as RELAY-MTAs. These RELAY-MTAs accept incoming connections from the RELAY-MTAs of the other MHS domains and in return are allowed to send messages to these RELAY-MTAs. A RELAY-MTA is documented with all the necessary connection information in the corresponding RELAY-MTA document. 4.3 The DOMAIN document An MHS domain has a responsible person who sets up the routing entries for the domain in the DOMAIN document. The primary RELAY- MTAs listed in the DOMAIN document as serving this MHS domain must, TOGETHER, offer at least connectivity to all networks and stacks listed as mandatory in the COMMUNITY document. Optional RELAY-MTAs may be added, generally with higher priority, to allow more precise routing. An MHS domain may also decide not to operate a RELAY-MTA. It will then only need agreements with one or more RELAY-MTAs from other MHS services which will relay for this domain. The domain itself, however, must either create its own DOMAIN document or document its MHS subtrees jointly with another MHS domain. Eppenberger [Page 4] RFC 1465 Routing Coordination for X.400 Services May 1993 The structure of the DOMAIN document is very straightforward. It starts off with one or more MHS subtrees, each on its own line. After the domains follows a line indicating the responsible person for the MHS subtrees mentioned. Finally the responsible RELAY-MTA(s) are listed with appropriate priorities. 4.4 The PERSON document All administrators and responsible persons are documented in PERSON documents. The RELAY-MTA and DOMAIN documents contain just keys pointing to a PERSON document. If such a person can already be found in an X.500 directory service, then the key consists of a Distinguished Name, else the key is just its OR address. 4.5 Coordination This approach requires an identified coordination point. It is up to the MHS community to decide on the level of coordination and support to be provided and on the funding mechanisms for such activities. Basic information can be found in the COMMUNITY document. The following list of support activities is considered mandatory for an operational service: - New RELAY-MTAs joining the service are tested and support is given to create the RELAY-MTA document. - New MHS domains joining the MHS community get assistance to set up RELAY-MTA(s) and/or find appropriate RELAY-MTA(s) and to create DOMAIN documents. - Updated documents are announced to the RELAY-MTA managers and responsible persons for the DOMAIN documents unless automatic distribution is used. - All the RELAY-MTA, DOMAIN and PERSON documents are made available on a file server together with the COMMUNITY document. The file server must at least be reachable via email. MHS communities with a big number of documents may consider additional access methods like ftp and FTAM. - Tools should be made available to manage routing tables for the X.400 software used on the RELAY-MTAs or to fill in and check the documents. The format of the documents has specifically been chosen to enable the use of automated tools. The RELAY-MTA managers must be aware that a large number of RELAY- MTAs in an MHS community may require significant operational resources to keep the local routing tables up-to-date and to Eppenberger [Page 5] RFC 1465 Routing Coordination for X.400 Services May 1993 constantly monitor the correct functioning of the connections. On the other hand more than one RELAY-MTA with a good connectivity to an MHS domain improves the overall robustness of the domain and thus the QOS. MHS communities may decide on additional mandatory requirements for the operation of a RELAY-MTA. These may include a hot line, echo services, exchange of statistics, response time to problem reports, uptime of the RELAY-MTA, etc. This will ensure a certain quality of service for the end users. 4.6 Routing The proposal addresses MHS communities spanning several organisations. But it may also be used to manage routing within a single organisation or even a global MHS community. Two kinds of mail relays are defined, the primary RELAY-MTAs and the secondary RELAY-MTAs. A primary or secondary RELAY-MTA must allow incoming connections from all other primary and secondary RELAY-MTAs with a common stack. Primary RELAY-MTAs must be able to connect to all other primary RELAY-MTAs which share a common stack. A secondary RELAY-MTA must connect to at least one primary RELAY-MTA. Each MHS community must define update procedures for the routing based on the documentation. Automated update has to be studied carefully. An MHS community should also define procedures for new RELAY-MTAs and MHS domains joining the service. Since the usage of X.400 is growing rapidly a flexible but well coordinated way of integrating new members into an MHS community is needed. The proposed documentation format supports this by allowing primary and secondary RELAY-MTAs. All RELAY-MTAs accept incoming connections from each other. Sending messages can be done by using the primary RELAY-MTAs only. This allows new RELAY-MTAs to join the community as secondary and to get primary status when traffic flow increases. Secondary RELAY-MTAs may also require a longer testing period. 5. The documents The definition is given in BNF-like syntax. The following conventions are used: | means choice \ is used for continuation of a definition over several lines Eppenberger [Page 6] RFC 1465 Routing Coordination for X.400 Services May 1993 [] means optional {} means repeated one or more times () is used to group choices \" is used for double quotes in a text string is a Carriage Return and means that the next section starts on its own line. The definition is complete only to a certain level of detail. Below this level, all expressions are to be replaced with text strings. Expressions without more detailed definition are marked with single quotes '. The format and semantics should be clear from the names of the expressions and the comments given. Wherever the BNF definition requires a single blank, multiple blanks may be used to increase the readability. Please note that for some field values the number of spaces is significant. Lines exceeding 80 characters should be wrapped at any convenient blank except at blanks which are significant. The line is continued with at least one leading blank. Comments may be placed anywhere in the document but only on separate lines and without splitting wrapped lines. Such a comment line must either start with a '#' sign followed by white space and the comment or consist of a single '#' on a single line. The documents must follow the case of the strings defined in BNF. Note that some values, especially connection parameters like TSEL or MTA password are case dependant too. The BNF definitions are ordered top-down. See Appendix B for an alphabetically sorted list. A set of one COMMUNITY document and several RELAY-MTA, DOMAIN and PERSON documents belong together. The detailed definitions can be found in the following chapters. ::= \ \ { } \ { } \ { } Eppenberger [Page 7] RFC 1465 Routing Coordination for X.400 Services May 1993 5.1 Common Definitions ::= 'Distinguished Name' The string representation of a Distinguished Name is defined in the RFCxxxx. If a Distinguished Name is used as a key in the documents, then the information can be fetched from the directory instead of checking the appropriate document. But as long as not all managers in the same community have directory access, the same information must also be present in a document. Note that Distinguished Names in the context of the routing documents are just used as key strings to point to other documents. ::= "Community: " \ ('community name' | ) The 'community name' is a string identifying the MHS community to be used in the first line of all documents. ::= (([ "P=" 'PRMDname' "; " ] \ ["A=" 'ADMDname' "; " ] \ "C=" "; " \ "MTAname=" 'MTAname') | ) A unique key is needed to identify the RELAY-MTA. In addition to the MTA name itself, it is proposed to use OR address attributes of the management domain where the RELAY-MTA resides. ADMD and PRMD fields are both optional and may be used to guarantee uniqueness of the key. The values used are irrelevant. Even non- printable characters like @ or ! are acceptable. The result is not an address but a key string. A Distinguished Name may be used instead. ::= ( | ) A unique key is necessary to make the links from the documents where a responsible person or an administrator is needed, to the PERSON documents. It is either the OR address of the person or a Distinguished Name (if the person is already registered in the directory). ::= 'Two Character Country Code ISO-3166' ::= 'OR address, ISO 10021-2 Annex F' It has been used consequently all over the document. This explains also the syntax of the Eppenberger [Page 8] RFC 1465 Routing Coordination for X.400 Services May 1993 and the . Examples: S=user; O=org ltd.; OU1=sect1; P=org; A=rel400; C=aq; DDA:RFC-822=we(a)sell.it; P=internet; A= ; C=xx; G=john; I=w; S=doe; P=org; A=rel400; C=aq; ::= "Address: " ::= [{"; " }] ::= {"+" " " \ [" x" ]} This syntax follows the attribute syntax of the X.500 directory based on CCITT E.123. ::= 'international prefix' ::= 'national telephone number' A national number may be written with spaces and hyphens to group the figures. ::= 'local extension' ::= "Phone: " One or more phone numbers ::= "Fax: " One or more FAX numbers ::= "Mail: " 'postal address information' The items of the postal address are separated by ' /' wherever the next item goes onto the next line for a printed address label. If the document is for an international community, the address should include the person's country. Example: Mail: SWITCH Head Office / Urs Eppenberger / Limmatquai 138 / CH-8001 Zurich / Switzerland results in the following mailing label: SWITCH Head Office Urs Eppenberger Limmatquai 138 CH-8001 Zurich Switzerland ::= "Update: FORMAT=V3; DATE=" 'yymmdd' \ "; START=" 'yymmdd' \ ["; END=" 'yymmdd'] The contains also the format identifier. Eppenberger [Page 9] RFC 1465 Routing Coordination for X.400 Services May 1993 The date of the last update of a document is given in the form 'yymmdd'. A start date must be set. A document can be published this way before the information in it is valid. (This is especially useful in absence of automated tools. RELAY-MTA managers get more time to prepare their systems.) An end date is used to set an expiration date for the document. ::= 'String encoded Presentation Address' The format of this string follows RFC1278, A string encoding of Presentation Address and RFC1277, Encoding Network Addresses to support operation over non-OSI layers. See chapter 5.2 about the usage of macros in a Presentation Address. ::= "/" \ "/" \ The service type consists of a string with three parts concatenated with a "/": Network-name/Network- service/Transport-Protocol. ::= 'Name of a network' The network-name string identifies a network. A well known key word should be chosen. (No '/' character is allowed.) Examples: Public-X.25, Internet, EMPB-X.25, Int-CLNS, WIN, Janet, ::= 'Name of a network service' Examples: X.25, CONS, CLNS, TCP ::= 'Name of a transport protocol' Examples: TP0, TP2, TP4, RFC1006 Since network and stack information forms one string, it identifies in an easy way a connection possibility between two RELAY-MTAs. The COMMUNITY document defines the strings to be used in the RELAY-MTA and DOMAIN documents. Some examples: Internet/TCP/RFC1006 Public-X.25/X.25/TP0 RARE-IXI/CONS/TP0 RARE-CLNS/CLNS/TP4 (It is probably important to mention here that this string has nothing to do with the format of a Eppenberger [Page 10] RFC 1465 Routing Coordination for X.400 Services May 1993 presentation address as defined by Steve Hardcastle- Kille in RFC1278. The problem of networks using the same address structure (X.121 DTEs, 4 Byte Internet addresses) but not being connected is not addressed in RFC1278 but solved by using the proposed service identifier above in addition to the presentation address. As long as there are network islands, there is no other way than the addition of an 'island'- identifier. ::= ["O=" 'Organization-name' "; "] \ ["OU1="'OrganizationalUnit'"; "\ ["OU2=" 'OrganizationalUnit' "; " \ ["OU3=" 'OrganizationalUnit' "; " \ ["OU4=" 'OrganizationalUnit' "; "]]]] \ ["P=" 'PRMDname' "; "] \ "A=" 'ADMDname' "; " \ "C=" ";" ::= "Reachable: " {