RFC 1777 (rfc1777) - Page 2 of 22
Lightweight Directory Access Protocol
Alternative Format: Original Text Document
RFC 1777 LDAP March 1995
implementations.
2. Protocol Model
The general model adopted by this protocol is one of clients
performing protocol operations against servers. In this model, this
is accomplished by a client transmitting a protocol request
describing the operation to be performed to a server, which is then
responsible for performing the necessary operations on the Directory.
Upon completion of the necessary operations, the server returns a
response containing any results or errors to the requesting client.
In keeping with the goal of easing the costs associated with use of
the Directory, it is an objective of this protocol to minimize the
complexity of clients so as to facilitate widespread deployment of
applications capable of utilizing the Directory.
Note that, although servers are required to return responses whenever
such responses are defined in the protocol, there is no requirement
for synchronous behavior on the part of either client or server
implementations: requests and responses for multiple operations may
be exchanged by client and servers in any order, as long as clients
eventually receive a response for every request that requires one.
Consistent with the model of servers performing protocol operations
on behalf of clients, it is also to be noted that protocol servers
are expected to handle referrals without resorting to the return of
such referrals to the client. This protocol makes no provisions for
the return of referrals to clients, as the model is one of servers
ensuring the performance of all necessary operations in the
Directory, with only final results or errors being returned by
servers to clients.
Note that this protocol can be mapped to a strict subset of the
directory abstract service, so it can be cleanly provided by the DAP.
3. Mapping Onto Transport Services
This protocol is designed to run over connection-oriented, reliable
transports, with all 8 bits in an octet being significant in the data
stream. Specifications for two underlying services are defined here,
though others are also possible.
3.1. Transmission Control Protocol (TCP)
The LDAPMessage PDUs are mapped directly onto the TCP bytestream.
Server implementations running over the TCP should provide a protocol
listener on port 389.
Yeong, Howes & Kille