Server-client communication over a network

Details Server-client communication over a network Server-client communication over a network

1998-03-20

2001-06-12

Amsbury, Wayne (Department: 2171)

Data processing: database and file management or data structures

Database design

Data structure types

C709S226000

Reexamination Certificate

active

06247017

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to communication between a server and a client over a telecommunications network, for example over the Internet. In particular, the invention finds application to communication over a telecommunications network employing directory services.
A directory service as provided in a telecommunications network, such as the Internet provides, is a physically distributed repository of data for managing the network. The purpose of the directory service is to locate and identify users and resources in the network. In the same manner as a telephone directory, the information can be classified by user or classification. Information about network components is stored in a distributed manner. The information is replicated in a number of network servers so that a user or service can refer to a local server for the information. Modifications made to the directory information are propagated to the replicated versions. In view of the need for replication, the directory service clearly works best if the information held is relatively static.
FIG. 1
of the accompanying drawings is a simple representation of a typical prior art Internet environment supporting a directory service
10
. In this environment, a directory service master
14
including a master directory database
16
is located on a first server
12
. Replication
18
is employed to create a replicated version of the directory service master database
16
on each of one or more remote server(s)
20
in one or more directory service slave database(s)
24
of one or more directory service slave(s)
22
. The replication mechanism, in order, for example, to replicate a modification of the directory service master database
16
on the directory service slave database(s)
24
, uses unsolicited messages between the directory service master
14
and each directory service slave
22
. The combination of the directory service master
14
and the directory service slave(s)
22
forms the directory service
10
. Only one remote server
20
with one directory service slave
22
and one directory service slave database
24
is shown in
FIG. 1
for illustrative purposes and ease of explanation. The replication
18
can be effected under a conventional directory service protocol, for example the Lightweight Directory Access Protocol (LDAP). Information about LDAP can be found, for example, in W Yeong, T Howes, and S. Kille, “Lightweight Directory Access Protocol”, RFC 1777, March 1995.
A Directory User Agent (DUA)
28
for a device or application (hereinafter termed an appliance)
26
is able to access the directory service
10
to read information from or to write information to the directory service
10
. The DUA
28
forms a directory user client for access to the directory service server(s)
12
/
20
. As shown in
FIG. 1
, the access is by way of the directory service master
14
, although it could equally be by way of a directory service slave
22
. It will be appreciated that there will typically be a large number of appliances and DUAs
28
requiring and making access to the directory service
10
. Only one appliance
26
and DUA
28
is shown in
FIG. 1
for illustrative purposes and ease of explanation only.
Access by the DUA
28
to the directory service
10
is by way of request
30
and response
32
messages under a conventional protocol, for example LDAP. This protocol enables clients to perform protocol operations with respect to servers. A client transmits a protocol request describing the operation to be performed to a server. The server then performs the required operations on the directory and returns one or more responses containing any results or errors to the requesting client.
An aim of the protocol is to minimise the complexity of clients. LDAP is designed to operate over a connection-oriented, reliable transport, with all
8
bits in an octet being significant in the data stream. For example, LDAP can operate over the Transmission Control Protocol (TCP) on the Internet (IP), with LDAP messages mapped directly onto the TCP bytestream.
It is well known that Internet usage is expanding at a phenomenal rate. As well as an ever increasing number of users making access, the type of information transfer which is occurring is changing. While the conventional structure described with reference to
FIG. 1
is quite efficient for information which is essentially static, it becomes network intensive when, for example, a DUA
28
needs to poll a variable, for example directory information about a particular user or network resource.
The invention seeks to provide a mechanism, method and system which seeks to eliminate or at least mitigate the problems associated with the conventional directory access mechanisms described above.
SUMMARY OF THE INVENTION
Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as appropriate and not merely as explicitly set out in the claims.
In accordance with a first aspect of the invention, there is provided a computer implemented method of updating a local record, or representation, of a variable in a network element forming a client of a directory service on a telecommunications network, the variable being maintained in a directory of the directory service. The method includes steps of, at the network element:
receiving a replication message from the directory service in respect of a change to the variable; and
responding to the replication message to update the local record of the variable.
By using a replication mechanism, an embodiment of the invention enables a network element automatically to be updated via a telecommunications network in response to changes to a variable in a directory service without repeatedly needing to poll the variable in the directory of the directory service.
In a preferred embodiment of the invention the network directory is an objectbased directory, for example an Internet directory service X.
500
directory. The replication messages can be LDAP replication messages.
The directory service can be arranged to associate with the variable a replication request in respect of the network element and to respond to changes to the variable to issue a replication message to the network element.
The replication request can be established by means of a filter for the variable which identifies at least the network element concerned. The directory service is thereby able to respond to changes to a variable to determine whether “polling” is required for the variable and to issue a replication message as the report message to the network element. The replication message can be an LDAP replication message.
The filter can be established manually by an operator of the directory service or could be established automatically in response to a request from the network element.
The local storage can be a cache for variables in the network element. The network element can be responsive to a request for a variable initially to access the cache, and in the absence of the variable in the cache, remotely to access the directory service for the variable.
The network element can, for example, be an appliance comprising a network service agent or other form of network device, or an application operable on a network device.
In accordance with another aspect of the invention, there is provided a network element comprising local storage for variables, a response mechanism configured to be operable to receive a replication message from a directory service in respect of a change to the variable at the directory service and to respond to the replication message to update the local record of the variable.
The request mechanism can be configured to be operable to transmit messages to a directory service of a network, the transmitted messages specifying operations on a variable of a directory in the directory service.
The invention also provides a directory service client comprising local storage

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