From ba8f85b49c38af7bc2a9acdef5dcde2de008d25e Mon Sep 17 00:00:00 2001 From: peter Date: Sat, 12 Jul 2008 05:00:28 +0000 Subject: Flatten bind9 vendor work area --- doc/rfc/rfc2163.txt | 1459 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1459 insertions(+) create mode 100644 doc/rfc/rfc2163.txt (limited to 'doc/rfc/rfc2163.txt') diff --git a/doc/rfc/rfc2163.txt b/doc/rfc/rfc2163.txt new file mode 100644 index 0000000..00fcee7 --- /dev/null +++ b/doc/rfc/rfc2163.txt @@ -0,0 +1,1459 @@ + + + + + + +Network Working Group C. Allocchio +Request for Comments: 2163 GARR-Italy +Obsoletes: 1664 January 1998 +Category: Standards Track + + + Using the Internet DNS to Distribute + MIXER Conformant Global Address Mapping (MCGAM) + +Status of this Memo + + This document specifies an Internet standards track protocol for the + Internet community, and requests discussion and suggestions for + improvements. Please refer to the current edition of the "Internet + Official Protocol Standards" (STD 1) for the standardization state + and status of this protocol. Distribution of this memo is unlimited. + +Copyright Notice + + Copyright (C) The Internet Society (1998). All Rights Reserved. + +Abstract + + This memo is the complete technical specification to store in the + Internet Domain Name System (DNS) the mapping information (MCGAM) + needed by MIXER conformant e-mail gateways and other tools to map + RFC822 domain names into X.400 O/R names and vice versa. Mapping + information can be managed in a distributed rather than a centralised + way. Organizations can publish their MIXER mapping or preferred + gateway routing information using just local resources (their local + DNS server), avoiding the need for a strong coordination with any + centralised organization. MIXER conformant gateways and tools located + on Internet hosts can retrieve the mapping information querying the + DNS instead of having fixed tables which need to be centrally updated + and distributed. + + This memo obsoletes RFC1664. It includes the changes introduced by + MIXER specification with respect to RFC1327: the new 'gate1' (O/R + addresses to domain) table is fully supported. Full backward + compatibility with RFC1664 specification is mantained, too. + + RFC1664 was a joint effort of IETF X400 operation working group + (x400ops) and TERENA (formely named "RARE") Mail and Messaging + working group (WG-MSG). This update was performed by the IETF MIXER + working group. + + + + + + +Allocchio Standards Track [Page 1] + +RFC 2163 MIXER MCGAM January 1998 + + +1. Introduction + + The connectivity between the Internet SMTP mail and other mail + services, including the Internet X.400 mail and the commercial X.400 + service providers, is assured by the Mail eXchanger (MX) record + information distributed via the Internet Domain Name System (DNS). A + number of documents then specify in details how to convert or encode + addresses from/to RFC822 style to the other mail system syntax. + However, only conversion methods provide, via some algorithm or a set + of mapping rules, a smooth translation, resulting in addresses + indistinguishable from the native ones in both RFC822 and foreign + world. + + MIXER describes a set of mappings (MIXER Conformant Global Address + Mapping - MCGAM) which will enable interworking between systems + operating the CCITT X.400 (1984/88/92) Recommendations and systems + using using the RFC822 mail protocol, or protocols derived from + RFC822. That document addresses conversion of services, addresses, + message envelopes, and message bodies between the two mail systems. + This document is concerned with one aspect of MIXER: the mechanism + for mapping between X.400 O/R addresses and RFC822 domain names. As + described in Appendix F of MIXER, implementation of the mappings + requires a database which maps between X.400 O/R addresses and domain + names; in RFC1327 this database was statically defined. + + The original approach in RFC1327 required many efforts to maintain + the correct mapping: all the gateways needed to get coherent tables + to apply the same mappings, the conversion tables had to be + distributed among all the operational gateways, and also every update + needed to be distributed. + + The concept of mapping rules distribution and use has been revised in + the new MIXER specification, introducing the concept of MIXER + Conformant Global Address Mapping (MCGAM). A MCGAM does not need to + be globally installed by any MIXER conformant gateway in the world + any more. However MIXER requires now efficient methods to publish its + MCGAM. + + Static tables are one of the possible methods to publish MCGAM. + However this static mechanism requires quite a long time to be spent + modifying and distributing the information, putting heavy constraints + on the time schedule of every update. In fact it does not appear + efficient compared to the Internet Domain Name Service (DNS). More + over it does not look feasible to distribute the database to a large + number of other useful applications, like local address converters, + e-mail User Agents or any other tool requiring the mapping rules to + produce correct results. + + + + +Allocchio Standards Track [Page 2] + +RFC 2163 MIXER MCGAM January 1998 + + + Two much more efficient methods are proposed by MIXER for publication + of MCGAM: the Internet DNS and X.500. This memo is the complete + technical specification for publishing MCGAM via Internet DNS. + + A first proposal to use the Internet DNS to store, retrieve and + maintain those mappings was introduced by two of the authors of + RFC1664 (B. Cole and R. Hagens) adopting two new DNS resource record + (RR) types: TO-X400 and TO-822. This proposal now adopts a more + complete strategy, and requires one new RR only. The distribution of + MCGAMs via DNS is in fact an important service for the whole Internet + community: it completes the information given by MX resource record + and it allows to produce clean addresses when messages are exchanged + among the Internet RFC822 world and the X.400 one (both Internet and + Public X.400 service providers). + + A first experiment in using the DNS without expanding the current set + of RR and using available ones was deployed by some of the authors of + RFC1664 at the time of its development. The existing PTR resource + records were used to store the mapping rules, and a new DNS tree was + created under the ".it" top level domain. The result of the + experiment was positive, and a few test applications ran under this + provisional set up. This test was also very useful in order to define + a possible migration strategy during the deployment of the new DNS + containing the new RR. The Internet DNS nameservers wishing to + provide this mapping information need in fact to be modified to + support the new RR type, and in the real Internet, due to the large + number of different implementations, this takes some time. + + The basic idea is to adopt a new DNS RR to store the mapping + information. The RFC822 to X.400 mapping rules (including the so + called 'gate2' rules) will be stored in the ordinary DNS tree, while + the definition of a new branch of the name space defined under each + national top level domain is envisaged in order to contain the X.400 + to RFC822 mappings ('table1' and 'gate1'). A "two-way" mapping + resolution schema is thus fully implemented. + + The creation of the new domain name space representing the X.400 O/R + names structure also provides the chance to use the DNS to distribute + dynamically other X.400 related information, thus solving other + efficiency problems currently affecting the X.400 MHS service. + + In this paper we will adopt the MCGAM syntax, showing how it can be + stored into the Internet DNS. + + + + + + + + +Allocchio Standards Track [Page 3] + +RFC 2163 MIXER MCGAM January 1998 + + +1.1 Definitions syntax + + The definitions in this document is given in BNF-like syntax, using + the following conventions: + + | means choice + \ is used for continuation of a definition over several lines + [] means optional + {} means repeated one or more times + + The definitions, however, are detailed only until a certain level, + and below it self-explaining character text strings will be used. + +2. Motivation + + Implementations of MIXER gateways require that a database store + address mapping information for X.400 and RFC822. This information + must be made available (published) to all MIXER gateways. In the + Internet community, the DNS has proven to be a practical mean for + providing a distributed name service. Advantages of using a DNS based + system over a table based approach for mapping between O/R addresses + and domain names are: + + - It avoids fetching and storing of entire mapping tables by every + host that wishes to implement MIXER gateways and/or tools + + - Modifications to the DNS based mapping information can be made + available in a more timely manner than with a table driven + approach. + + - It allows full authority delegation, in agreement with the + Internet regionalization process. + + - Table management is not necessarily required for DNS-based + MIXER gateways. + + - One can determine the mappings in use by a remote gateway by + querying the DNS (remote debugging). + + Also many other tools, like address converters and User Agents can + take advantage of the real-time availability of MIXER tables, + allowing a much easier maintenance of the information. + +3. The domain space for X.400 O/R name addresses + + Usual domain names (the ones normally used as the global part of an + RFC822 e-mail address) and their associated information, i.e., host + IP addresses, mail exchanger names, etc., are stored in the DNS as a + + + +Allocchio Standards Track [Page 4] + +RFC 2163 MIXER MCGAM January 1998 + + + distributed database under a number of top-level domains. Some top- + level domains are used for traditional categories or international + organisations (EDU, COM, NET, ORG, INT, MIL...). On the other hand + any country has its own two letter ISO country code as top-level + domain (FR, DE, GB, IT, RU, ...), including "US" for USA. The + special top-level/second-level couple IN-ADDR.ARPA is used to store + the IP address to domain name relationship. This memo defines in the + above structure the appropriate way to locate the X.400 O/R name + space, thus enabling to store in DNS the MIXER mappings (MCGAMs). + + The MIXER mapping information is composed by four tables: + + - 'table1' and 'gate1' gives the translation from X.400 to RFC822; + - 'table2' and 'gate2' tables map RFC822 into X.400. + + Each mapping table is composed by mapping rules, and a single mapping + rule is composed by a keyword (the argument of the mapping function + derived from the address to be translated) and a translator (the + mapping function parameter): + + keyword#translator# + + the '#' sign is a delimiter enclosing the translator. An example: + + foo.bar.us#PRMD$foo\.bar.ADMD$intx.C$us# + + Local mappings are not intended for use outside their restricted + environment, thus they should not be included in DNS. If local + mappings are used, they should be stored using static local tables, + exactly as local static host tables can be used with DNS. + + The keyword of a 'table2' and 'gate2' table entry is a valid RFC822 + domain; thus the usual domain name space can be used without problems + to store these entries. + On the other hand, the keyword of a 'table1' and 'gate1' entry + belongs to the X.400 O/R name space. The X.400 O/R name space does + not usually fit into the usual domain name space, although there are + a number of similarities; a new name structure is thus needed to + represent it. This new name structure contains the X.400 mail + domains. + + To ensure the correct functioning of the DNS system, the new X.400 + name structure must be hooked to the existing domain name space in a + way which respects the existing name hierarchy. + + A possible solution was to create another special branch, starting + from the root of the DNS tree, somehow similar to the in-addr.arpa + tree. This idea would have required to establish a central authority + + + +Allocchio Standards Track [Page 5] + +RFC 2163 MIXER MCGAM January 1998 + + + to coordinate at international level the management of each national + X.400 name tree, including the X.400 public service providers. This + coordination problem is a heavy burden if approached globally. More + over the X.400 name structure is very 'country oriented': thus while + it requires a coordination at national level, it does not have + concepts like the international root. In fact the X.400 international + service is based on a large number of bilateral agreements, and only + within some communities an international coordination service exists. + + The X.400 two letter ISO country codes, however, are the same used + for the RFC822 country top-level domains and this gives us an + appropriate hook to insert the new branches. The proposal is, in + fact, to create under each national top level ISO country code a new + branch in the name space. This branch represents exactly the X.400 + O/R name structure as defined in each single country, following the + ADMD, PRMD, O, OU hierarchy. A unique reserved label 'X42D' is placed + under each country top-level domain, and hence the national X.400 + name space derives its own structure: + + . (root) + | + +-----------------+-----------+--------+-----------------+... + | | | | + edu it us fr + | | | | + +---+---+... +-----+-----+... +-----+-----+... +--+---+... + | | | | | | | | | | + ... ... cnr X42D infn va ca X42D X42D inria + | | | | + +------------+------------+... ... ... +----+-------+... + | | | | | + ADMD-PtPostel ADMD-garr ADMD-Master400 ADMD-atlas ADMD-red + | | | | + +----------+----+... ... +-------+------+... ... + | | | | + PRMD-infn PRMD-STET PRMD-Telecom PRMD-Renault + | | | | + ... ... ... ... + + + The creation of the X.400 new name tree at national level solves the + problem of the international coordination. Actually the coordination + problem is just moved at national level, but it thus becomes easier + to solve. The coordination at national level between the X.400 + communities and the Internet world is already a requirement for the + creation of the national static MIXER mapping tables; the use of the + Internet DNS gives further motivations for this coordination. + + + + +Allocchio Standards Track [Page 6] + +RFC 2163 MIXER MCGAM January 1998 + + + The coordination at national level also fits in the new concept of + MCGAM pubblication. The DNS in fact allows a step by step authority + distribution, up to a final complete delegation: thus organizations + whishing to publish their MCGAM just need to receive delegation also + for their branch of the new X.400 name space. A further advantage of + the national based solution is to allow each country to set up its + own X.400 name structure in DNS and to deploy its own authority + delegation according to its local time scale and requirements, with + no loss of global service in the mean time. And last, placing the new + X.400 name tree and coordination process at national level fits into + the Internet regionalization and internationalisation process, as it + requires local bodies to take care of local coordination problems. + + The DNS name space thus contains completely the information required + by an e-mail gateway or tool to perform the X.400-RFC822 mapping: a + simple query to the nearest nameserver provides it. Moreover there is + no more any need to store, maintain and distribute manually any + mapping table. The new X.400 name space can also contain further + information about the X.400 community, as DNS allows for it a + complete set of resource records, and thus it allows further + developments. This set of RRs in the new X.400 name space must be + considered 'reserved' and thus not used until further specifications. + + The construction of the new domain space trees will follow the same + procedures used when organising at first the already existing DNS + space: at first the information will be stored in a quite centralised + way, and distribution of authority will be gradually achieved. A + separate document will describe the implementation phase and the + methods to assure a smooth introduction of the new service. + +4. The new DNS resource record for MIXER mapping rules: PX + + The specification of the Internet DNS (RFC1035) provides a number of + specific resource records (RRs) to contain specific pieces of + information. In particular they contain the Mail eXchanger (MX) RR + and the host Address (A) records which are used by the Internet SMTP + mailers. As we will store the RFC822 to X.400 mapping information in + the already existing DNS name tree, we need to define a new DNS RR in + order to avoid any possible clash or misuse of already existing data + structures. The same new RR will also be used to store the mappings + from X.400 to RFC822. More over the mapping information, i.e., the + MCGAMs, has a specific format and syntax which require an appropriate + data structure and processing. A further advantage of defining a new + RR is the ability to include flexibility for some eventual future + development. + + + + + + +Allocchio Standards Track [Page 7] + +RFC 2163 MIXER MCGAM January 1998 + + + The definition of the new 'PX' DNS resource record is: + + class: IN (Internet) + + name: PX (pointer to X.400/RFC822 mapping information) + + value: 26 + + The PX RDATA format is: + + +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ + | PREFERENCE | + +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ + / MAP822 / + / / + +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ + / MAPX400 / + / / + +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ + + where: + + PREFERENCE A 16 bit integer which specifies the preference given to + this RR among others at the same owner. Lower values + are preferred; + + MAP822 A element containing , the + RFC822 part of the MCGAM; + + MAPX400 A element containing the value of + derived from the X.400 part of + the MCGAM (see sect. 4.2); + + PX records cause no additional section processing. The PX RR format + is the usual one: + + [] [] + + When we store in DNS a 'table1' or a 'gate1' entry, then will + be an X.400 mail domain name in DNS syntax (see sect. 4.2). When we + store a 'table2' or a 'gate2' table entry, will be an RFC822 + mail domain name, including both fully qualified DNS domains and mail + only domains (MX-only domains). All normal DNS conventions, like + default values, wildcards, abbreviations and message compression, + apply also for all the components of the PX RR. In particular , + MAP822 and MAPX400, as elements, must have the final + "." (root) when they are fully qualified. + + + + +Allocchio Standards Track [Page 8] + +RFC 2163 MIXER MCGAM January 1998 + + +4.1 Additional features of the PX resource record + + The definition of the RDATA for the PX resource record, and the fact + that DNS allows a distinction between an exact value and a wildcard + match for the parameter, represent an extension of the MIXER + specification for mapping rules. In fact, any MCGAM entry is an + implicit wildcard entry, i.e., the rule + + net2.it#PRMD$net2.ADMD$p400.C$it# + + covers any RFC822 domain ending with 'net2.it', unless more detailed + rules for some subdomain in 'net2.it' are present. Thus there is no + possibility to specify explicitly a MCGAM as an exact match only + rule. In DNS an entry like + + *.net2.it. IN PX 10 net2.it. PRMD-net2.ADMD-p400.C-it. + + specify the usual wildcard match as for MIXER tables. However an + entry like + + ab.net2.it. IN PX 10 ab.net2.it. O-ab.PRMD-net2.ADMDb.C-it. + + is valid only for an exact match of 'ab.net2.it' RFC822 domain. + + Note also that in DNS syntax there is no '#' delimiter around MAP822 + and MAPX400 fields: the syntax defined in sect. 4.2 in fact does not + allow the (ASCII decimal 32) character within these fields, + making unneeded the use of an explicit delimiter as required in the + MIXER original syntax. + + Another extension to the MIXER specifications is the PREFERENCE value + defined as part of the PX RDATA section. This numeric value has + exactly the same meaning than the similar one used for the MX RR. It + is thus possible to specify more than one single mapping for a domain + (both from RFC822 to X.400 and vice versa), giving as the preference + order. In MIXER static tables, however, you cannot specify more than + one mapping per each RFC822 domain, and the same restriction apply + for any X.400 domain mapping to an RFC822 one. + + More over, in the X.400 recommendations a note suggests than an + ADMD= should be reserved for some special cases. Various + national functional profile specifications for an X.400 MHS states + that if an X.400 PRMD is reachable via any of its national ADMDs, + independently of its actual single or multiple connectivity with + them, it should use ADMD= to advertise this fact. Again, if a + PRMD has no connections to any ADMD it should use ADMD=0 to notify + its status, etc. However, in most of the current real situations, the + ADMD service providers do not accept messages coming from their + + + +Allocchio Standards Track [Page 9] + +RFC 2163 MIXER MCGAM January 1998 + + + subscribers if they have a blank ADMD, forcing them to have their own + ADMD value. In such a situation there are problems in indicating + properly the actually working mappings for domains with multiple + connectivity. The PX RDATA 'PREFERENCE' extension was introduced to + take in consideration these problems. + + However, as these extensions are not available with MIXER static + tables, it is strongly discouraged to use them when interworking with + any table based gateway or application. The extensions were in fact + introduced just to add more flexibility, like the PREFERENCE value, + or they were already implicit in the DNS mechanism, like the + wildcard specification. They should be used very carefully or just + considered 'reserved for future use'. In particular, for current use, + the PREFERENCE value in the PX record specification should be fixed + to a value of 50, and only wildcard specifications should be used + when specifying values. + +4.2 The DNS syntax for an X.400 'domain' + + The syntax definition of the MCGAM rules is defined in appendix F of + that document. However that syntax is not very human oriented and + contains a number of characters which have a special meaning in other + fields of the Internet DNS. Thus in order to avoid any possible + problem, especially due to some old DNS implementations still being + used in the Internet, we define a syntax for the X.400 part of any + MCGAM rules (and hence for any X.400 O/R name) which makes it + compatible with a element, i.e., + + ::= | " " + ::=