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rfc:ien:ien89

IEN 89

                                  
                                  
                        Internet Name Server
                                  
                                  
                                  
                                  
                             Jon Postel
                             2 May 1979
                                  
                                  
                                  
                                  
                   Information Sciences Institute
                 University of Southern California
                         4676 Admiralty Way
                 Marina del Rey, California  90291
                           (213) 822-1511

IEN-89 J. Postel

                                                                   ISI
                                                            2 May 1979
                        INTERNET NAME SERVER
                        --------------------

INTRODUCTION


This memo defines the procedure to access an Internet Name Server. Such a server provides the actual addresses of hosts in the internet when supplied with a host name. An Internet Name Server is a dynamic name-to-number translation service.

This server utilizes the User Datagram Protocol (UDP) [2], which in turn calls on the Internet Protocol (IN) [3].

NAME SYNTAX


It is strongly recommended that the use of host names in programs be consistent for both input and output across all hosts. To promote such consistency of the internet level, the following syntax is specified:

The SYNTAX of names as presented to the user and as entered by the user is:

| NET | REST
where:
  NET is a network name or number as defined in [1]
and
  REST is a host name within  that network  expressed  as a  character
  string  or as a number.   When  a number is used, it is expressed in
  decimals and is prefixed with a sharp sign (e.g., #1234).
Note that this syntax  has minimal  impact  on the allowable character
strings for host names within a network.  The only restriction is that
a REST string cannot begin with an exclamation point (|).
The |NET|  may be omitted when specifying a host in the local network.
That is "|" indicates the network portion of a name string.

Postel [page 1]

                                                            2 May 1979

Internet Name Server IEN 89

NAME SERVER


To aid in the translation of names to internet addresses, several name server processes will be provided. The name server process will accept a name in the above form and will return a name, address pair.

The name server processes will have well-known addresses; addresses that are constant over long periods of time and published in documents such as [1].

A request sent to a name server is sent as a user datagram [2] with the following content:

  +--------+--------+--------+--------+--------+--------+---\\---+
  |        |        |                                            |
  |  NAME  | LENGTH |                NAME STRING                 |
  |        |        |                                            |
  +--------+--------+--------+--------+--------+--------+---\\---+
where:
  NAME is a one octet code indicating that the following is a name,
  LENGTH  is a one octet  count  of the number  of octets  in the name
  string, and
  NAME STRING is an ASCII character string of the form | NET | REST.

A reply to a successful translation is sent as a user datagram with the following content:

  +--------+--------+--------+--------+--------+--------+---\\---+
  |        |        |                                            |
  |  NAME  | LENGTH |                NAME STRING                 |
  |        |        |                                            |
  +--------+--------+--------+--------+--------+--------+---\\---+
  |        |        |                                   |         
  | ADDRESS| LENGTH |         INTERNET ADDRESS          |         
  |        |        |                                   |         
  +--------+--------+--------+--------+--------+--------+         

[page 2] Postel

2 May 1979 IEN 89 Internet Name Server

where:
  ADDRESS  is a one octet  code indicating  that the following  is  an
  internet address,
  LENGTH  is a one octet  count  (=4)  of the length  of the  internet
  address, and
  INTERNET ADDRESS is the internet address.

Actually a particular name might map to several internet addresses, in this case the response would include a list of internet addresses.

When a name is not found, an error is reported via a user datagram as follows:

  +--------+--------+--------+--------+--------+--------+---\\---+
  |        |        |                                            |
  |  NAME  | LENGTH |                NAME STRING                 |
  |        |        |                                            |
  +--------+--------+--------+--------+--------+--------+---\\---+
  |        |        |  ERROR |                                   |
  | ERROR  | LENGTH |  CODE  |       ERROR STRING                |
  |        |        |        |                                   |
  +--------+--------+--------+--------+--------+--------+---\\---+
where:
  ERROR CODE specifies the error.
  ERROR STRING explains the error.

Error Codes

The following error codes are defined:
  CODE          MEANING
  ----          -------
   0            Undetermined or undefined error
   1            Name not found
   2            Improper name syntax
   3            Name not found, but the following similar names exist
Note Error 3 is followed by a list of name strings.

Postel [page 3]

                                                            2 May 1979

Internet Name Server IEN 89

Communication with a Name Server Process

Communication  with a name server process is via user datagrams.  User
datagrams   do  not  guarantee  reliable  communication.   Thus,  some
requests or replies may be lost.
The  name  server   process   is  a  transaction   oriented   process;
furthermore,  the  nature  of  the  transactions  allows  them  to  be
processed in any order and even to be duplicated.  This allows the use
of a very simple communication protocol.
If a request  is made to the name server  process  and no response  is
received  within a reasonable time, then the requester should make the
request  again.   This recovers  from communication errors which cause
the loss of either the request or the reply.
In order  to use this simple  strategy,  care must be taken  to  allow
replies to be properly matched with requests.  The name server process
does this by including in each reply a copy of the entire request.
The user datagram  protocol  does provide a checksum for the detection
of errors.

Format

The requests and replies to and from a name server process are encoded
as "items".   An item consists  of an item-code an item-length and the
item-data.   The item-length  includes in its count the item-count and
the item-length octets.
  Item  :=  Item-Code  Item-Length  Item-Data
  +--------+--------+--------+--------+--------+--------+---\\---+
  |        |        |                                            |
  |  Item  |  Item  |               Item                         |
  |  Code  | Length |                      Data                  |
  |        |        |                                            |
  +--------+--------+--------+--------+--------+--------+---\\---+
A request is typically one item, and a reply is typically two items.

[page 4] Postel

2 May 1979 IEN 89 Internet Name Server

                                  
               +--------+--------+--------+--------+
               |ItemCode|Item Len|... Item Data ...|
               +--------+--------+--------+--------+
               | ......... Item Data cont ........ |
               +--------+--------+--------+--------+
               | Item Data cont. |ItemCode|Item Len|
               +--------+--------+--------+--------+
               | ........... Item Data ........... |
               +--------+--------+--------+--------+

Item Code Value Assignments:

NAME    = 1
ADDRESS = 2
ERROR   = 3

Example

a typical request:
                                  
               +-----------------+--------+--------+
               |   1    |   12   |   |    |   A    |
               +--------+--------+--------+--------+
               |   R    |   P    |   A    |   |    |
               +--------+--------+--------+--------+
               |   I    |   S    |   I    |   B    |
               +--------+--------+--------+--------+

Postel [page 5]

                                                            2 May 1979

Internet Name Server IEN 89

and the reply:
                                  
               +-----------------+--------+--------+
               |   1    |   12   |   |    |   A    |
               +--------+--------+--------+--------+
               |   R    |   P    |   A    |   |    |
               +--------+--------+--------+--------+
               |   I    |   S    |   I    |   B    |
               +--------+--------+--------+--------+
               |   2    |   6    |   10   |   3    |
               +--------+--------+--------+--------+
               |   0    |   52   |                  
               +--------+--------+                  

[page 6] Postel

2 May 1979 IEN 89 Internet Name Server References

References


[1] J. Postel. "Assigned Numbers," RFC 755, IEN 93, May 1979.

[2] J. Postel. "User Datagram Protocol," IEN 88, USC-Information

      Sciences Institute, May 1979.

[3] J. Postel. "Internet Datagram Protocol – Version 4," IEN 80,

      USC-Information Sciences Institute, February 1979.

Postel [page 7]

/data/webs/external/dokuwiki/data/pages/rfc/ien/ien89.txt · Last modified: 2001/06/25 18:49 by 127.0.0.1

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