rfc1202.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

Network Working Group                                            M. Rose
Request for Comments: 1202       Performance Systems International, Inc.
                                                           February 1991


                      Directory Assistance Service

Status of this Memo

   This document defines a mechanism by which a user-interface may
   access a textual DAP-like interface over a TCP/IP connection.  This
   is a local mechanism.  This memo provides information for the
   Internet community.  It does not specify any standard.  Distribution
   of this memo is unlimited.

Table of Contents

   1. Introduction ..........................................   1
   1.1 An Aside ............................................    3
   2. Protocol ..............................................   3
   2.1 Control Connection ..................................    4
   2.1.1 Initialization ....................................    4
   2.1.2 Transactions ......................................    4
   2.1.2.1 INTR command ....................................    4
   2.1.2.2 STAT command ....................................    5
   2.1.2.3 QUIT command ....................................    5
   2.2 Data Connection .....................................    5
   2.2.1 Transactions ......................................    5
   2.2.2 Responses .........................................    6
   2.2.2.1 Numeric Responses ...............................    6
   2.2.2.2 'm' Response ....................................    6
   2.2.2.3 'y' Response ....................................    6
   2.2.2.4 'p' Response ....................................    7
   2.2.2.5 'e' Response ....................................    7
   2.2.2.6 'l' Response ....................................    7
   2.2.2.7 'd' Response ....................................    8
   2.2.2.8 'P' Response ....................................    8
   3. Example Interaction ...................................   9
   4. References ............................................  10
   5. Security Considerations...............................   11
   6. Author's Address......................................   11

1.  Introduction

   The OSI Directory [1] provides a powerful infrastructure for the
   retrieval of information objects.  This infrastructure can be used to
   support, e.g., white pages applications, application entity lookup,
   and so on.



Rose                                                            [Page 1]

RFC 1202              Directory Assistance Service         February 1991


   The Directory service is provided to applications through the
   Directory Access Protocol (DAP), which binds a Directory User Agent
   (DUA) to a Directory System Agent (DSA).

                                        | Directory Service
                                        |    provided via DAP
                                        |
               +-----------+            |            +-----------+
               |           |            |            |           |
               |    DUA    | <----------+----------> |    DSA    |
               |           |            |            |           |
               +-----------+            |            +-----------+
                                        |
                         Directory User |

   The DAP is an OSI application layer protocol which uses the rich OSI
   upper-layer infrastructure.  Unfortunately, the coding investment to
   implement the DAP is significant.  As such, it is difficult to host
   applications using the Directory on smaller workstations and personal
   computers.

   This memo details a local mechanism which has been successfully used
   to separate the functionality of the DAP from the complexity of
   implementing the DAP.  That is, a split-DUA model is used: the DAP is
   implemented on an entity (the "Directory Assistant"), which resides
   on a capable workstation or mainframe and exports a simpler
   interface, the "Directory Assistance" (DA) protocol, to other end-
   systems where the user-interface resides, termed the DA-client.

   Since this mechanism provides assistance to applications wishing to
   access the Directory, it is termed the "Directory Assistance" (DA)
   service:



















Rose                                                            [Page 2]

RFC 1202              Directory Assistance Service         February 1991


                                        | Directory Service
                 split-DUA              |    provided via DAP
                                        |
               +-----------+            |            +-----------+
               |           |            |            |           |
               | Directory | <----------+----------> |    DSA    |
               | Assistant |            |            |           |
               |           |            |            +-----------+
               +-----------+            |
                    /|\                 |
                     |                  |
                     | DA-service       |
                     |   provide via    |
                     |   DA-protocol    |
                     |                  |
               ------+------            |
                     |                  |
                     |                  |
                     |                  |
                     |                  |
                     |                  |
                    \|/                 |
               +-----------+            |
               |           |            |
               | DA-client |            |
               |           |            |
               +-----------+            |
                                        |
                         Directory User |


1.1.  An Aside

   This memo documents an already existing protocol, which was
   originally used to provide a split-DUA model within the same host.
   In the absence of detailed historical and implementational
   understanding, some of the mechanisms described may not appear
   intuitive.

2.  Protocol

   The DA service operates using two TCP connections: a control
   connection, and a data connection.  The control connection defines
   the lifetime of an instance of the DA service; throughout this
   lifetime, several data connections may be established.  However, at
   any given instant, between zero and one data connections will be in
   progress.




Rose                                                            [Page 3]

RFC 1202              Directory Assistance Service         February 1991


   The DA service is provided by the "Directory Assistant", which
   consists of two entities: a DA-server, which manages the control
   connection; and, a DAP-listener, which responds to commands on the
   data connection.  The DA-server oversees the behavior of the DAP-
   listener.

2.1.  Control Connection

   Data sent over the control connection consists of a series of
   transactions.  NVT-ASCII is used to express these transactions.  Each
   transaction consists of the client sending a directive--a line of
   text terminated by CR-LF; the DA-server returns a response--a line of
   text terminated by CR-LF.  All responses from a DA-server start with
   either "+OK" or "-ERR" depending on whether the transaction was
   successful.

2.1.1.  Initialization

   A DA-server listens on TCP port 411 for incoming connections.  Upon
   establishing a control connection, the DA-server returns a response
   indicating whether the service has been started.  If successful, the
   response contains an IP-address and a TCP port, expressed in NVT-
   ASCII, and separated by one or more instances of the space character.
   This information corresponds to the TCP-endpoint that the DAP-
   listener will use for the data connection.

   Note that the DA-server and DAP-listener need not reside at the same
   IP-address.  In the future, DA-servers may employ a internal protocol
   for load-balancing purposes.

   If the DA service can not be started, an error response is returned
   and the control connection is closed.


2.1.2.  Transactions

   All transactions with the DA-server consist of a command followed by
   zero or more arguments, separated by the space character.

2.1.2.1.  INTR command

   The INTR command takes no arguments.

   The INTR command is used to interrupt any DAP transaction
   currently in progress.

   The INTR command always returns success.




Rose                                                            [Page 4]

RFC 1202              Directory Assistance Service         February 1991


2.1.2.2.  STAT command

   The STAT command takes no arguments.

   The STAT command is used to verify that the DAP-listener is
   available.

   The STAT command returns success only if the DAP-listener is
   still active.

2.1.2.3.  QUIT command

   The QUIT command takes no arguments.

   The QUIT command is used to terminate the DA service.

   The QUIT command always returns success.

2.2.  Data Connection

   Data sent over a data connection consists of a single DAP-
   transaction.  NVT-ASCII is used to express these transactions.  Each
   transaction consists of the client sending a command--a line of text
   terminated by the LF-character; the DAP-listener returns zero or more
   responses, each with a specific termination sequence.  All responses
   from a DAP-listener start with a single identifying character.  If
   the character is a digit (0-9), then the termination sequence
   consists of a closing the data connection; otherwise, if the
   character is a lower-case letter (a-z), then the response is
   interactive and is terminated by the LF-character.

2.2.1.  Transactions

   All transactions with the DAP-listener consist of a command followed
   by zero or more arguments, separated by the space character.
   Double-quotes may be used to prevent separation of tokens.

   The command set is taken from the DISH program:

               add         add a new entry
               bind        connect to the Directory
               compare     compare entry's attribute
               delete      delete an entry
               fred        back-end to FrED
               list        list children
               modify      modify an existing entry
               modifyrdn   modify an entry's name
               moveto      move to a position



Rose                                                            [Page 5]

RFC 1202              Directory Assistance Service         February 1991


               search      search for an object
               showentry   show an entry
               showname    show an entry's name
               squid       status of dish
               unbind      disconnect from the Directory

   See [2] for a complete list of commands and arguments.

   Note that commands and arguments are in lower-case, and may
   abbreviated to any unique prefix.

2.2.2.  Responses

   There are two kinds of responses: numeric-responses, which consist of
   arbitrary text; and, letter-responses, which consist of brief text,
   and expect further interaction from the client.

2.2.2.1.  Numeric Responses

   If the response is '1', then the DAP-transaction terminated normally;
   if the response is '2', then the DAP-transaction failed; if the
   response is '3', then the DAP-transaction was a search returning more
   than one result and one of the -hitone or -list option was selected
   for the search; if the response is '4', then the DAP-transaction