Type of Architecture

Client server application/Web server application

Points: It is a network architecture which separates a client from a server.

• The client software can send request to a server.
• Server includes web server, application server, file server, terminal server and mail server.

Ex: if you are browsing an online store, your computer and web browser would be considered a client and the computer, data and application that make up the online store would be considered the server. When your web browser request a particular page from the online store, the server finds all of the information required to display the article in the database, assembles it into a web page and send it back to your web browser for you to look at.

Characteristics of a Server:
• Passive (slave)
• Waits for the request
• Upon receipts of request, processes them and then server’s replies.

Characteristics of a Client:
• Active (master)

• Sends request

• Waits for and receives server replies

Servers are two types,
• State full server and Stateless

A State less server does not keep any information b/w requests
A State full server can remember information b/w requests.
Ex: An HTTP server for static HTML pages is a stateless server,
While Apache Tomcat is an example of a state full server

The interaction b/w client & server are often described using sequence diagrams. It is a standardized in the UML (Unified Modular Language).

Peer to Peer Architecture: Is another types of network architecture because each node or instance of the program is both a client and a server and each has equivalent responsibilities.

Tiered Architecture: Generic client/server architecture has two types of nods on the network client and server. This is called as “two-tier architecture”.

Some network will consists of three different kinds o f nodes.

Client, application server, which process data for the client and data base server which store data for the application server. This is called 3 tier architecture.

Advantages of n-tier architecture with two tier architecture
1. It separates out the processing that occurs to better balance the load on the different server.
2. It is more scalable

Disadvantages:
1. It puts more loads on the network.
2. It is much more difficult to program and test software than in two-tier architecture because more devices have to communicate to complete a user’s transaction.

Thin client Vs thick client:
Thin client (sometimes also called lean client) is a client computer or client software in client server architecture network which depends primarily on the central server for processing activities and mainly focus on convening input and output b/w the user and the remote server.

Thick client or fat client server does as much processing as possible and passes only data for communications and storages to the server.

Environment:

Environment is a combination of 3 layers:
• Presentation Layer
• Business layer
• Data base layer

Types of Environment:
There are 4 types of environments:
1. Stand alone environment/ one-tier architecture
2. Client server environment/two-tier architecture
3. Distributed environment/ n- tier architecture

1. Stand alone environment (or) one tier architecture:
This environment contains all the three layer i.e. presentation layer, business layer, and data base layer single tier.

2. Client server environment or two tier architecture:
In this environment two tiers will be there one tier is for client and other tier is for database server. Presentation layer and business layer will be present in each and every client and the database will be present in database server.

3. Web environment: In this environment three tiers will be there client resides in one tier, application server resides in middle tier and database server resides in the last tier. Every client will have the presentation layer, application server will have the business layer and database server will have the database layer.

4. Distributed environment: it is same as the web environment but the business logic is distributed among application server is order to distribute the load.

Web server: It is software that provides web services to the client

Application server: It is server that holds the business logic.
Ex: Tomcat, web logic, web spear etc…

Comparison with the MVC architecture:
MVC – Model view controller

A fundamental rule in three tier architecture is the client – tier never communicates directly with the data tier in a three – tier model. All communication must pass through the middle ware tier.
The three tier architecture is linear. MVC is a triangle the view sends update to the controller, the controller updates the model and the view gets updated directly from the model.

Web development usage:
Three tiers are often used to refer to web sites.
1. A front end web servers serving static content.
2. A middle dynamic content processing and generation level application servers for ex: java EE platform.
3. A back end database, comprising both data sets and the database management system or RDBMS software that manager and provides access to the data.

Application and Web Servers:
Web server serves pages for viewing in a web browser, while an application server provides method that client application can call.

A web server exclusively handles HTTP request, whereas an application server serves business logic to applications programs through any number of protocols.