Network Working Group                               K. Harrenstien (SRI)
Request for Comments: 953                                 M. Stahl (SRI)
Obsoletes:  RFC 811                                     E. Feinler (SRI)
                                                            October 1985

                            HOSTNAME SERVER


STATUS OF THIS MEMO

   This RFC is the official specification of the Hostname Server
   Protocol.  This edition of the specification includes minor revisions
   to RFC 811 which brings it up to date.  Distribution of this memo is
   unlimited.

INTRODUCTION

   The NIC Internet Hostname Server is a TCP-based host information
   program and protocol running on the SRI-NIC machine.  It is one of a
   series of internet name services maintained by the DDN Network
   Information Center (NIC) at SRI International on behalf of the
   Defense Communications Agency (DCA).  The function of this particular
   server is to deliver machine-readable name/address information
   describing networks, gateways, hosts, and eventually domains, within
   the internet environment.  As currently implemented, the server
   provides the information outlined in the DoD Internet Host Table
   Specification [See RFC-952].  For a discussion of future developments
   see also RFC-921 concerning the Domain Name System.

PROTOCOL

   To access this server from a program, establish a TCP connection to
   port 101 (decimal) at the service host, SRI-NIC.ARPA (26.0.0.73 or
   10.0.0.51).  Send the information request (a single line), and read
   the resulting response.  The connection is closed by the server upon
   completion of the response, so only one request can be made for each
   connection.

QUERY/RESPONSE FORMAT

   The name server accepts simple text query requests of the form

      <command key> <argument(s)> [<options>]

   where square brackets ("[]") indicate an optional field.  The command
   key is a keyword indicating the nature of the request.  The defined
   keys are explained below.

   The response, on the other hand, is of the form

      <response key> : <rest of response>

   where <response key> is a keyword indicating the nature of the
   response, and the rest of the response is interpreted in the context
   of the key.

   NOTE:  Care should be taken to interpret the nature of the reply
   (e.g, single record or multiple record), so that no confusion about
   the state of the reply results.  An "ALL" request will likely return
   several hundred or more records of all types, whereas "HNAME" or
   "HADDR" will usually return one HOST record.

COMMAND/RESPONSE KEYS

   The currently defined command keywords are listed below.  NOTE:
   Because the server and the features available will evolve with time,
   the HELP command should be used to obtain the most recent summary of
   implemented features, changes, or new commands.

      Keyword   Response

      HELP      This information.

      VERSION   "VERSION: <string>" where <string> will be different for
                each version of the host table.

      HNAME <hostname>
                One or more matching host table entries.

      HADDR <hostaddr>
                One or more matching host table entries.

      ALL       The entire host table.

      ALL-OLD   The entire host table without domain style names.

      DOMAINS   The entire top-level domain table (domains only).

      ALL-DOM   Both the entire domain table and the host table.

      ALL-INGWAY
                All known gateways in TENEX/TOPS-20 INTERNET.GATEWAYS
                format.

   Remember that the server accepts only a single command line and
   returns only a single response before closing the connection.  HNAME
   and HADDR are useful for looking up a specific host by name or
   address; VERSION can be used by automated processes to see whether a
   "new" version of the host table exists without having to transfer the

   whole table.  Note, however, that the returned version string is only
   guaranteed to be unique to each version, and nothing should currently
   be assumed about its format.

   Response Keys:

      ERR       entry not found, nature of error follows
      NET       entry found, rest of entry follows
      GATEWAY   entry found, rest of entry follows
      HOST      entry found, rest of entry follows
      DOMAIN    entry found, rest of entry follows
      BEGIN     followed by multiple entries
      END       done with BEGIN block of entries

   More keywords will be added as new needs are recognized.  A more
   detailed description of the allowed requests/responses follows.

QUERY/RESPONSE EXAMPLES

   1. HNAME Query - Given a name, find the entry or entries that match
   the name.  For example:

      HNAME SRI-NIC.ARPA <CRLF>

         where <CRLF> is a carriage return/ linefeed, and 'SRI-NIC.ARPA'
         is a host name

      The likely response is:

      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 :

      A response may stretch across more than one line.  Continuation
      lines always begin with at least one space.

   2. HADDR Query - Given an internet address (as specified in RFC 796)
   find the entry or entries that match that address. For example:

      HADDR 26.0.0.73 <CRLF>

         where <CRLF> is a carriage return/ linefeed, and '26.0.0.73' is
         a host address.

      The likely response is the same as for the previous HNAME request.

   3. ALL Query - Deliver the entire internet host table in a
   machine-readable form.  For example:

      ALL <CRLF>   ;where <CRLF> is a carriage return/linefeed

      The likely response is the keyword 'BEGIN' followed by a colon
      ':', followed by the entire internet host table in the format
      specified in RFC-952, followed by 'END:'.

ERROR HANDLING

   ERR Reply - may occur on any query, and should be permitted in any
   access program using the name server.  Errors are of the form

      ERR : <code> : <string> :
        as in
      ERR : NAMNFD : Name not found :

   The error code is a unique descriptor, limited to 8 characters in
   length for any given error.  It may be used by the access program to
   identify the error and, in some cases, to handle it automatically.
   The string is an accompanying message for a given error for that case
   where the access program simply logs the error message.  Current
   codes and their associated interpretations are

      NAMNFD    Name not found; name not in table
      ADRNFD    Address not found; address not in table
      ILLCOM    Illegal command; command key not recognized
      TMPSYS    Temporary system failure, try again later

REFERENCES

   1. Harrenstien, K., Stahl, M., and Feinler, E., "Official DoD
      Internet Host Table Specification," RFC-952, DDN Network
      Information Center, SRI International, October 1985.

   2. Pickens, J., Feinler, E., and Mathis, J., "The NIC Name Server," A
      Datagram-based Information Utility, RFC-756, Network Information
      Center, SRI International, July 1979.

   3. Postel, J., "Address Mappings," RFC-796, Information Sciences
      Institute, University of Southern California, Marina del Rey,
      September 1981.

   4. Postel, J., "Domain Name System Implementation Schedule", RFC-921,
      Information Sciences Institute, University of Southern California,
      Marina del Rey, October 1984.