Technology client – server, widely used when working with databases in the network, known for a long time and most often applied in large organizations. Today, with the development of INTERNET, this technology is increasingly attracting the attention of software developers, because the world has accumulated vast amounts of information on various issues and often, this information is stored in databases.

The network architecture defines the basic elements of the network, characterizes its overall logical organization, technical support, software, describes methods of encoding. The architecture also defines the principles of operation and user interface.

Architecture client – server (client-server architecture) – this is the concept of information network, for the majority of its resources concentrated in the servers, serving its customers. The architecture defines two types of components: servers and clients.

 The server is an object, giving service to other network entities upon request. Service is the process of customer service.

The server is running on the tasks of clients and manages the execution of their tasks. After each task, the server sends the results to the client, who sent the job.

Service function in the architecture of client – server describes a complex application programs, which performs a variety of applied processes.

The process, which invokes the service function with certain operations, called by the client. They may be program or user. In figure. 2 the following list of services in the architecture of client – server.

Clients are workstations, which use server resources and provides convenient user interfaces. The user interfaces is user interaction with the system or network.

The client is the initiator and uses e-mail or other server services. In this process the client requests service, establishes a session, receives the results and reports on completion of work.

In networks with a dedicated file server on a dedicated stand-alone PC installed network server operating system. This PC becomes a server. Software (ON), installed on the workstation, allows her to communicate with the server. The most common network operating systems:

- Novel NetWare company;

- Windows NT Microsoft;

- UNIX company AT &T;

- Linux.

In addition to network operating system network application, take advantage of, provided by the network.

Network-based servers have better features and improved reliability. The server owns the main network resources, are accessed by the other workstations.

In modern client – server architecture, there are four groups of objects: customers, servers, data and network services.Customers are in the system on the user desktop. Data is mostly stored in the servers. Network services are a shared server and data. Additionally, services run by the data-processing procedures.

Network client – server architecture have the following advantages:

- Allow to organize the network with a large number of workstations;

- Provide centralized management of user accounts, security and access, which simplifies network administration;

- Effective access to network resources;

- The user needs one password to log into the network and to gain access to all resources, subject to the rights of the user.

Along with the advantages of client – server architectures have some disadvantages:

- Faulty servers can make the network unusable, at least the loss of network resources;

- Require a qualified staff for administration;

- Have a higher value of networks and network equipment.