Software Architecture

1. Client /server architecture:

The client process sends a request to the server. The server interprets the message and then attempts to fulfill the request. In order to fulfill the request, the server may have to refer to a knowledge source (database), process data (perform calculations), control a peripheral, or make an additional request of another server. In many architectures, a client can make requests of multiple servers and a server can service multiple clients.

Characteristics of a client:

Initiates requests

Waits for replies

Receives replies

Usually connects to a small number of servers at one time

Typically interacts directly with end-users using a graphical user interface

Characteristics of a sever:

Never initiates requests or activities

Waits for and replies to requests from connected clients

A server can remotely install/uninstall applications and transfer data to the intended clients 

2. 2-tier architecture:

It is client/server architecture, where a request to do some task is sent to the server and the server responds by performing that task.

Two-tier client/server architectures have 2 essential components

1. A Client PC and

2. A Database Server

3. 3-tier architecture: In 3-tier architecture, the processing is divided between two or more servers, one used for application processing and another for database processing. I.e. A separate computer (application server) performs the data processing, although some part may still be handled by the user's machine.

3-Tier client-server architectures have 3 essential components:

1. A Client PC

2. An Application Server

3. A Database Server

4. N-tier architecture: The term ‘N-tier’ refers to the possibility of having some N-no of configurations. I.e. client / database / layers / elements etc.

The n-tier architecture is the same as the 3-tier architecture, but it has multiple (n) component and data management servers. It can distribute components across multiple servers and can access data in multiple databases.