Network Working Group A. Cooper Request for Comments: 1480 J. Postel Obsoletes: 1386 June 1993 The US Domain Status of this Memo This memo provides information for the Internet community. It does not specify an Internet standard. Distribution of this memo is unlimited. Table of Contents 1. Introduction ................................................ 2 1.1 The Internet Domain Name System......................... 2 1.2 Top-Level Domains....................................... 3 1.3 The US Domain .......................................... 4 2. Naming Structure ............................................ 4 2.1 State Codes ............................................ 8 2.2 Locality Names.......................................... 8 2.3 Schools ................................................ 10 2.4 State Agencies.......................................... 15 2.5 Federal Agencies ....................................... 15 2.6 Distributed National Institutes......................... 15 2.7 General Independent Entities............................ 16 2.8 Examples of Names....................................... 17 3. Registration ................................................ 20 3.1 Requirements ........................................... 20 3.2 Direct Entries ......................................... 21 3.2.1 IP-Hosts............................................. 21 3.2.2 Non-IP Hosts ........................................ 21 3.3 Delegated Subdomains ................................... 24 3.3.1 Delegation Requirement............................... 26 3.3.2 Delegation Procedures ............................... 28 3.3.3 Subdomain Contacts................................... 29 4. Database Information......................................... 30 4.1 Name Servers ........................................... 30 4.2 Zone files ............................................. 30 4.3 Resource Records ....................................... 31 4.3.1 "A" Records ......................................... 32 4.3.2 CNAME Records ....................................... 32 4.3.3 MX Records .......................................... 33 4.3.4 HINFO Records ....................................... 33 4.3.5 PTR Records ......................................... 33 4.4 Wildcards .............................................. 34 5. References .................................................. 35 Cooper & Postel [Page 1] RFC 1480 The US Domain June 1993 6. Security Considerations ..................................... 35 7. Authors' Addresses .......................................... 36 Appendix-I: US Domain Names BNF................................. 37 Appendix-II: US Domain Questionnaire ............................ 42 1. INTRODUCTION 1.1 The Internet Domain Name System The Domain Name System (DNS) provides for the translation between hostnames and addresses. Within the Internet, this means translating from a name such as "venera.isi.edu", to an IP address such as "128.9.0.32". The DNS is a set of protocols and databases. The protocols define the syntax and semantics for a query language to ask questions about information located by DNS-style names. The databases are distributed and replicated. There is no dependence on a single central server, and each part of the database is provided in at least two servers. The assignment of the 32-bit IP addresses is a separate activity. IP addresses are delegated by the central Internet Registry to regional authorities (such as the RIPE NCC for Europe) and the network providers. To have a network number assigned please contact your network service provider or regional registration authority. To determine who this is (or as a last resort), you can contact the central Internet Registry at Hostmaster@INTERNIC.NET. In addition to translating names to addresses for hosts that are on the Internet, the DNS provides for registering DNS-style names for other hosts reachable (via electronic mail) through gateways or mail relays. The records for such name registrations point to an Internet host (one with an IP address) that acts as a mail forwarder for the registered host. For example, the host "bah.rochester.ny.us" is registered in the DNS with a pointer to the mail relay "relay1.uu.net". This type of pointer is called an MX record. This gives electronic mail users a uniform mail addressing syntax and avoids making users aware of the underlying network boundaries. The reason for the development of the domain system was growth in the Internet. The hostname to address mappings were maintained by the InterNIC in a single file, called HOSTS.TXT, which was FTP'd by all the hosts on the Internet. The network population was changing in character. The time-share hosts that made up the original ARPANET were being replaced with local networks of workstations. Local organizations were administering their own names and addresses, but Cooper & Postel [Page 2] RFC 1480 The US Domain June 1993 had to wait for the NIC to make changes in HOSTS.TXT to make the changes visible to the Internet at large. Organizations also wanted some local structure on the name space. The applications on the Internet were getting more sophisticated and creating a need for general purpose name service. The idea of a hierarchical name space, with the hierarchy roughly corresponding to organizational structure, and names using "." as the character to mark the boundary between hierarchy levels was developed. A design using a distributed database and generalized resources was implemented. The DNS provides standard formats for resource data, standard methods for querying the database, and standard methods for name servers to refresh local data from other name servers. 1.2 Top-Level Domains The top-level domains in the DNS are EDU, COM, GOV, MIL, ORG, INT, and NET, and all the 2-letter country codes from the list of countries in ISO-3166. The establishment of new top-level domains is managed by the Internet Assigned Numbers Authority (IANA). The IANA may be contacted at IANA@ISI.EDU. Even though the original intention was that any educational institution anywhere in the world could be registered under the EDU domain, in practice, it has turned out with few exceptions, only those in the United States have registered under EDU, similarly with COM (for commercial). In other countries, everything is registered under the 2-letter country code, often with some subdivision. For example, in Korea (KR) the second level names are AC for academic community, CO for commercial, GO for government, and RE for research. However, each country may go its own way about organizing its domain, and many have. There are no current plans of putting all of the organizational domains EDU, GOV, COM, etc., under US. These name tokens are not used in the US Domain to avoid confusion. Currently, only four year colleges and universities are being registered in the EDU domain. All other schools are being registered in the US Domain. There are also concerns about the size of the other top-level domains (especially COM) and ideas are being considered for restructuring. Other names sometimes appear as top-level domain names. Some people have made up names in the DNS-style without coordinating or registering with the DNS management. Some names that typically appear are BITNET, UUCP, and two-letter codes for continents, such as Cooper & Postel [Page 3] RFC 1480 The US Domain June 1993 "NA" for North America (this conflicts with the official Internet code for Namibia). For example, the DNS-style name "KA7EEJ.CO.USA.NA" is used in the amateur radio network. These addresses are never supposed to show up on the Internet but they do occasionally. The amateur radio network people created their own naming scheme, and it interferes sometimes with Internet addresses. 1.3 The US Domain The US Domain is an official top-level domain in the DNS of the Internet community. The domain administrators are Jon Postel and Ann Westine Cooper at the Information Sciences Institute of the University of Southern California (USC-ISI). US is the ISO-3166 2-letter country code for the United States and thus the US Domain is established as a top-level domain and registered with the InterNIC the same way other country domains are. Because organizations in the United States have registered primarily in the EDU and COM domains, little use was initially made of the US domain. In the past, the computers registered in the US Domain were primarily owned by small companies or individuals with computers at home. However, the US Domain has grown and currently registers hosts in federal government agencies, state government agencies, K12 schools, community colleges, technical/vocational schools, private schools, libraries, city and county government agencies, to name a few. Initially, the administration of the US Domain was managed solely by the Domain Registrar. However, due to the increase in registrations, administration of subdomains is being delegated to others. Any computer in the United States may be registered in the US Domain. 2. NAMING STRUCTURE The US Domain hierarchy is based on political geography. The basic name space under US is the state name space, then the "locality" name space, (like a city, or county) then organization or computer name and so on. For example: BERKELEY.CA.US PORTLAND.WA.US Cooper & Postel [Page 4] RFC 1480 The US Domain June 1993 There is of course no problem with running out of names. The things that are named are individual computers. If you register now in one city and then move, the database can be updated with a new name in your new city, and a pointer can be set up from your old name to your new name. This type of pointer is called a CNAME record. The use of unregistered names is not effective and causes problems for other users. Inventing your own name and using it without registering is not a good idea. In addition to strictly geographically names, some special names are used, such as FED, STATE, AGENCY, DISTRICT, K12, LIB, CC, CITY, and COUNTY. Several new name spaces have been created, DNI, GEN, and TEC, and a minor change under the "locality" name space was made to the existing CITY and COUNTY subdomains by abbreviating them to CI and CO. A detailed description follows. Below US, Parallel to States: ----------------------------- "FED" - This branch may be used for agencies of the federal government. For example: ..FED.US "DNI" - DISTRIBUTED NATIONAL INSTITUTES - The "DNI" branch was created directly under the top-level US. This branch is to be used for distributed national institutes; organizations that span state, regional, and other organizational boundaries; that are national in scope, and have distributed facilities. For example: .DNI.US. Name Space Within States: ------------------------ "locality" - cities, counties, parishes, and townships. Subdomains under the "locality" would be like CI...US, CO...US, or businesses. For example: Petville.Marvista.CA.US. "CI" - This branch is used for city government agencies and is a subdomain under the "locality" name (like Los Angeles). For example: Fire-Dept.CI.Los-Angeles.CA.US. "CO" - This branch is used for county government agencies and is a subdomain under the "locality" name (like Los Angeles). For example: Fire-Dept.CO.San-Diego.CA.US. Cooper & Postel [Page 5] RFC 1480 The US Domain June 1993 "K12" - This branch may be used for public school districts. A special name "PVT" can be used in the place of a school district name for private schools. For example: .K12..US and .PVT.K12..US. "CC" - COMMUNITY COLLEGES - This branch was established for all state wide community colleges. For example: .CC..US. "TEC" - TECHNICAL AND VOCATIONAL SCHOOLS - The branch "TEC" was established for technical and vocational schools and colleges. For example: .TEC..US. "LIB" - LIBRARIES (STATE, REGIONAL, CITY, COUNTY) - This branch may be used for libraries only. For example: .LIB..US. "STATE" - This branch may be used for state government agencies. For example: .STATE..US. "GEN" - GENERAL INDEPENDENT ENTITY - This branch is for the things that don't fit easily into any other structure listed -- things that might fit in to something like ORG at the top-level. It is best not to use the same keywords (ORG, EDU, COM, etc.) that are used at the top-level to avoid confusion. GEN would be used for such things as, state-wide organizations, clubs, or domain parks. For example: .GEN..US. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ VIEW OF SECOND LEVEL DOMAINS UNDER US +-------+ | US | +-------+ | +----------------------------------+ | | | | | +-----+ +-----+ +-----+ +-----+ +-----+ | FED | | DNI | | TX | | SD | | CA | +-----+ +-----+ +-----+ +-----+ +-----+ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Cooper & Postel [Page 6] RFC 1480 The US Domain June 1993 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ SCHOOL AND LIBRARY VIEW +-----+ | CA | +-----+ | +------------------------------------------------+ | | | | | +-----+ +-----+ +-----+ +-------------+ +-----+ | K12 | | CC | | TEC | | LOS ANGELES | | LIB | +-----+ +-----+ +-----+ +-------------+ +-----+ / \ /|\ /|\ /|\ /|\ +--------+ +---+ +---+ +--------+ +----------+ +------+ |sch dist| |PVT| |SJC| |WM TRADE| |pvt school| |MALIBU| +--------+ +---+ +---+ +--------+ +----------+ +------+ /|\ /|\ +--------+ +--------+ |sch name| |sch name| +--------+ +--------+ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ VIEW OF STATE, REGIONAL, and GENERAL AGENCIES +-----+ | CA | +-----+ | +-------------------------+ | | | +-------+ +--------+ +-----+ | STATE | |DISTRICT| | GEN |