RFC 952

DoD Internet host table specification

📅 published October 1985, from ietf

DOD INTERNET HOST TABLE SPECIFICATION 💖

okay bestie, meet RFC 952 🎀

Request for Comments: 952 and it's from the Network Working Group. The authors are K. Harrenstien (SRI), M. Stahl (SRI), and E. Feinler (SRI). It's dated October 1985. It Obsoletes: RFC 810, 608, so those two are officially retired 💀 The header doesn't list a category or anything it updates, so I'm not making those up 🙈

STATUS OF THIS MEMO ✨

this is the official spec for the format of the Internet Host Table 💅 This edition has minor revisions to RFC-810 to bring it up to date. Distribution of this memo is unlimited 🌈

INTRODUCTION 🦋

The DoD Host Table is used by the DoD Hostname Server. That server is maintained by the DDN Network Information Center (NIC) on behalf of the Defense Communications Agency (DCA) [See RFC-953].

LOCATION OF THE STANDARD DOD ONLINE HOST TABLE 🍓

A machine-translatable ASCII text version of the DoD Host Table lives online in the file NETINFO:HOSTS.TXT on the SRI-NIC host. You can grab it over FTP from your local host by connecting to SRI-NIC.ARPA (26.0.0.73 or 10.0.0.51), logging in with user = ANONYMOUS and password = GUEST, and then retrieving "NETINFO:HOSTS.TXT". The same table MAY also be obtained through the NIC Hostname Server, as described in RFC-953. That method is faster and easier, but it requires a user program to make the necessary connection to the Name Server 🫶

ASSUMPTIONS 🧚

A "name" (Net, Host, Gateway, or Domain name) is a text string of up to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus sign (-), and period (.). Periods are only allowed when they separate the pieces of "domain style names" (see RFC-921, "Domain Name System Implementation Schedule", for background). No blank or space characters are allowed as part of a name. Upper and lower case are treated the same. The first character MUST be an alpha character. The last character MUST NOT be a minus sign or period. A host which serves as a GATEWAY SHOULD have "-GATEWAY" or "-GW" as part of its name. Hosts which do not serve as Internet gateways SHOULD NOT use "-GATEWAY" and "-GW" as part of their names. A host which is a TAC SHOULD have "-TAC" as the last part of its host name, if it is a DoD host. Single character names or nicknames are not allowed.
Internet Addresses are 32-bit addresses [See RFC-796]. In the host table described here, each address is written as four decimal numbers separated by a period. Each decimal number represents 1 octet.
If the first bit of the first octet of the address is 0 (zero), then the next 7 bits of the first octet indicate the network number (Class A Address). If the first two bits are 1,0 (one,zero), then the next 14 bits define the net number (Class B Address). If the first 3 bits are 1,1,0 (one,one,zero), then the next 21 bits define the net number (Class C Address) [See RFC-943]. Here's the diagram 📐

      +-+------------+--------------+--------------+--------------+
      |0|  NET <-7-> |         LOCAL ADDRESS <-24->               |
      +-+------------+--------------+--------------+--------------+

      +---+----------+--------------+--------------+--------------+
      |1 0|      NET  <-14->        |  LOCAL ADDRESS <-16->       |
      +---+----------+--------------+--------------+--------------+

      +-----+--------+--------------+--------------+--------------+
      |1 1 0|            NET  <-21->               | LOCAL ADDRESS|
      +-----+--------+--------------+--------------+--------------+

The LOCAL ADDRESS portion of the internet address identifies a host within the network specified by the NET portion of the address.
The ARPANET and MILNET are both Class A networks. The NET portion is 10 decimal for ARPANET and 26 decimal for MILNET. The LOCAL ADDRESS maps as follows: the second octet identifies the physical host, the third octet identifies the logical host, and the fourth identifies the Packet Switching Node (PSN), formerly known as an Interface Message Processor (IMP).

      +-+------------+--------------+--------------+--------------+
      |0|  10 or 26  |    HOST      | LOGICAL HOST |   PSN (IMP)  |
      +-+------------+--------------+--------------+--------------+

(NOTE: RFC-796 also describes the local address mappings for several other networks.)

It is the responsibility of the users of this host table to translate it into whatever format is needed for their purposes.
Names and addresses for DoD hosts and gateways will be negotiated and registered with the DDN PMO, and subsequently with the NIC, before being used and before traffic is passed by a DoD host. Names and addresses for domains and networks are to be registered with the DDN Network Information Center (HOSTMASTER@SRI-NIC.ARPA) or 800-235-3155.

The NIC will attempt to keep similar information for non-DoD networks and hosts, if this information is provided, and as long as it is needed. In other words, that continues until intercommunicating network name servers are in place 👑

EXAMPLE OF HOST TABLE FORMAT 🎀

   NET : 10.0.0.0 : ARPANET :
   NET : 128.10.0.0 : PURDUE-CS-NET :
   GATEWAY : 10.0.0.77, 18.10.0.4 : MIT-GW.ARPA,MIT-GATEWAY : PDP-11 :
             MOS : IP/GW,EGP :
   HOST : 26.0.0.73, 10.0.0.51 : SRI-NIC.ARPA,SRI-NIC,NIC : DEC-2060 :
          TOPS20 :TCP/TELNET,TCP/SMTP,TCP/TIME,TCP/FTP,TCP/ECHO,ICMP :
   HOST : 10.2.0.11 : SU-TAC.ARPA,SU-TAC : C/30 : TAC : TCP :

SYNTAX AND CONVENTIONS 💜

   ; (semicolon)   is used to denote the beginning of a comment.
                   Any text on a given line following a ';' is a
                   comment, and not part of the host table.

   NET             keyword introducing a network entry

   GATEWAY         keyword introducing a gateway entry

   HOST            keyword introducing a host entry

   DOMAIN          keyword introducing a domain entry

   :(colon)        is used as a field delimiter

   ::(2 colons)    indicates a null field

   ,(comma)        is used as a data element delimiter

   XXX/YYY         indicates protocol information of the type
                   TRANSPORT/SERVICE.

Where TRANSPORT/SERVICE options are specified as:

         "FOO/BAR"       both transport and service known
         "FOO"           transport known; services not known

         "BAR"           service is known, transport not known

         NOTE:  See "Assigned Numbers" for specific options and acronyms
         for machine types, operating systems, and protocol/services.

Each host table entry is an ASCII text string made up of 6 fields. Here's the rundown 🌸

Field 1 is the KEYWORD that says whether the entry is about a NET, GATEWAY, HOST, or DOMAIN. NET entries are assigned and cannot have alternate addresses or nicknames. DOMAIN entries do not use fields 4, 5, or 6.
Field 2 is the Internet Address of the Network, Gateway, or Host, followed by any alternate addresses. Addresses for a Domain are the ones where a Domain Name Server exists for that domain.
Field 3 is the Official Name of the Network, Gateway, Host, or Domain, with OPTIONAL nicknames where they're permitted.
Field 4 is the Machine Type.
Field 5 is the Operating System.
Field 6 is the Protocol List.

Fields 4, 5 and 6 are OPTIONAL. For a Domain they are not used. Fields 3-6, if included, pertain to the first address in Field 2.

"Blanks" (spaces and tabs) are ignored between data elements or fields, but they're disallowed within a data element. Each entry ends with a colon.

The entries in the table are grouped by type, in the order Domain, Net, Gateway, and Host. Within each type the ordering is unspecified.

Note that although OPTIONAL nicknames are allowed for hosts, they're discouraged. The one exception is when host names have been changed and both the new and the old names are kept for a suitable period of time to make the switch smooth. Nicknames are not permitted for NET names 💅

GRAMMATICAL HOST TABLE SPECIFICATION 🦋

A. Parsing grammar 🧚

      <entry> ::= <keyword> ":" <addresses> ":" <names> [":" [<cputype>]
         [":" [<opsys>]  [":" [<protocol list>] ]]] ":"
      <addresses> ::= <address> *["," <address>]
      <address> ::= <octet> "." <octet> "." <octet> "." <octet>
      <octet> ::= <0 to 255 decimal>
      <names> ::= <netname> | <gatename> | <domainname> *[","
         <nicknames>]
         | <official hostname> *["," <nicknames>]
      <netname>  ::= <name>
      <gatename> ::= <hname>
      <domainname> ::= <hname>
      <official hostname> ::= <hname>
      <nickname> ::= <hname>
      <protocol list> ::= <protocol spec> *["," <protocol spec>]
      <protocol spec> ::= <transport name> "/" <service name>
         | <raw protocol name>

B. Lexical grammar 🌈

      <entry-field> ::= <entry-text> [<cr><lf> <blank> <entry-field>]
      <entry-text>  ::= <print-char> *<text>
      <blank> ::= <space-or-tab> [<blank>]
      <keyword> ::= NET | GATEWAY | HOST | DOMAIN
      <hname> ::= <name>*["."<name>]
      <name>  ::= <let>[*[<let-or-digit-or-hyphen>]<let-or-digit>]
      <cputype> ::= PDP-11/70 | DEC-1080 | C/30 | CDC-6400...etc.
      <opsys>   ::= ITS | MULTICS | TOPS20 | UNIX...etc.
      <transport name> ::= TCP | NCP | UDP | IP...etc.
      <service name> ::= TELNET | FTP | SMTP | MTP...etc.
      <raw protocol name> ::= <name>
      <comment> ::= ";" <text><cr><lf>
      <text>    ::= *[<print-char> | <blank>]
      <print-char>  ::= <any printing char (not space or tab)>

Notes:

Zero or more 'blanks' between separators " , : " are allowed. 'Blanks' are spaces and tabs.
Continuation lines are lines that begin with at least one blank. They MAY be used anywhere 'blanks' are legal to split an entry across lines.

BIBLIOGRAPHY 📚

Feinler, E., Harrenstien, K., Su, Z. and White, V., "Official DoD Internet Host Table Specification", RFC-810, Network Information Center, SRI International, March 1982.
Harrenstien, K., Stahl, M., and Feinler, E., "Hostname Server", RFC-953, Network Information Center, SRI International, October 1985.
Kudlick, M. "Host Names Online", RFC-608, Network Information Center, SRI International, January 1973.
Postel, J., "Internet Protocol", RFC-791, Information Sciences Institute, University of Southern California, Marina del Rey, September 1981.
Postel, J., "Address Mappings", RFC-796, Information Sciences Institute, University of Southern California, Marina del Rey, September 1981.
Postel, J., "Domain Name System Implementation Schedule", RFC-921, Information Sciences Institute, University of Southern California, Marina del Rey, October 1984.
Reynolds, J. and Postel, J., "Assigned Numbers", RFC-943, Information Sciences Institute, University of Southern California, Marina del Rey, April 1985.

📦 where this page comes from

ietf: rfc952 1985-10
💖 girlified by claude-haiku-5-5 on 2026-10-19: a language model's rewrite of the original, under its terms