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
[]
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
:
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Hostname Server
where 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: " where will be different for
each version of the host table.
HNAME
One or more matching host table entries.
HADDR
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
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Hostname Server
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
where 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
where 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.
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Hostname Server
3. ALL Query - Deliver the entire internet host table in a
machine-readable form. For example:
ALL ;where 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 : : :
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.
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RFC, FYI, BCP