Connection-less Lightweight X.500 Directory Access Protocol
RFC 1798

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Network Working Group                                           A. Young
Request for Comments: 1798                              ISODE Consortium
Category: Standards Track                                      June 1995

       Connection-less Lightweight X.500 Directory Access Protocol

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

X.500

   The protocol described in this document is designed to provide access
   to the Directory while not incurring the resource requirements of the
   Directory Access Protocol (DAP) [3].  In particular, it is aimed at
   avoiding the elapsed time that is associated with connection-oriented
   communication and it facilitates use of the Directory in a manner
   analagous to the DNS [5,6].  It is specifically targeted at simple
   lookup applications that require to read a small number of attribute
   values from a single entry.  It is intended to be a complement to DAP
   and LDAP [4].  The protocol specification draws heavily on that of
   LDAP.

1.  Background

   The Directory can be used as a repository for many kinds of
   information.  The full power of DAP is unnecessary for applications
   that require simple read access to a few attribute values.
   Applications addressing is a good example of this type of use where
   an application entity needs to determine the Presentation Address
   (PA) of a peer entity given that peer's Application Entity Title
   (AET). If the AET is a Directory Name (DN) then the required result
   can be obtained from the PA attribute of the Directory entry
   identified by the AET.  This is very similar to DNS.

Young                       Standards Track                     [Page 1]
RFC 1798                         CLDAP                         June 1995

   Use of DAP to achieve this functionality involves a significant
   number of network exchanges:

      ___________________________________________________________
     |_#_|______Client_(DUA)________DAP________Server_(DSA)_____|
     |  1|  N-Connect.request       ->                          |
     |  2|                          <-    N-Connect.response    |
     |  3|  T-Connect.request       ->                          |
     |  4|                          <-    T-Connect.response    |
     |   |  S-Connect.request,                                  |
     |   |  P-Connect.request,                                  |
     |   |  A-Associate.request,                                |
     |  5|  DAP-Bind.request        ->                          |
     |   |                                S-Connect.response,   |
     |   |                                P-Connect.response,   |
     |   |                                A-Associate.response, |
     |  6|                          <-    DAP-Bind.response     |
     |  7|  DAP-Read.request        ->                          |
     |  8|                          <-    DAP-Read.response     |
     |   |  S-Release.request,                                  |
     |   |  P-Release.request,                                  |
     |   |  A-Release.request,                                  |
     |  9|  DAP-Unbind.request      ->                          |
     |   |                                S-Release.response,   |
     |   |                                P-Release.response,   |
     |   |                                A-Release.response,   |
     | 10|                          <-    DAP-Unbind.response   |
     |   |  T-Disconnect.request,                               |
     | 11|  N-Disconnect.request    ->                          |
     |   |                                T-Disconnect.response,|
     | 12|                          <-    N-Disconnect.response |
     |___|______________________________________________________|

Young                       Standards Track                     [Page 2]
RFC 1798                         CLDAP                         June 1995

   This is 10 packets before the application can continue, given that it
   can probably do so after issuing the T-Disconnect.request.  (Some
   minor variations arise depending upon the class of Network and
   Transport service that is being used; for example use of TP4 over
   CLNS reduces the packet count by two.) LDAP is no better in the case
   where the LDAP server uses full DAP to communicate with the
   Directory:

  ____________________________________________________________________
 |__#_|___Client_____LDAP_____LDAP_server______DAP_________DSA_______|
 |  1 |  TCP SYN      ->                                             |
 |  2 |               <-    TCP SYN ACK                              |
 |  3 |  BindReq      ->                                             |