Web Architectures

Web App Architectures: 1- tier,2-tier,3-tier,n-tier.

1-tier Architecture:

All 3 layers are on same machine 
Presentation,Business Logic,Database are tightly connected.
Scalability: Single processor means hard to increase the volume of processing speed.
Portability:  Moving to new machine may mean rewriting every thing.
Maintenance: Changing one layer requires to change  in other layers.

2-tier Architecture:

The Two-tier architecture is divided into two parts:

1) Client Application (Client Tier)
2) Database (Data Tier)

The two-tier is based on Client Server architecture. The two-tier architecture is like client server application. The direct communication takes place between client and server. There is no intermediate between client and server. Because of tight coupling a 2 tiered application will run faster

• Database runs on Server 
• Separated from client
• Easy to switch to different databases
• Presentation and logic layers still tightly connected

Advantages:

1. Easy to maintain and modification is bit easy
2. Communication is faster

Disadvantages:

1. In two tier architecture application performance will be degrade upon increasing the users.
2. Cost-ineffective 

 3-tier Architecture:

Three-tier architecture typically comprise a presentation tier, a business or data access tier, and a data tier. Three layers in the three tier architecture are as follows:

1) Client layer
2) Business layer
3) Data layer

1) Client layer:
It is also called as Presentation layer which contains UI part of our application. This layer is used for the design purpose where data is presented to the user or input is taken from the user. For example designing registration form which contains text box, label, button etc.
2) Business layer:
In this layer all business logic written like validation of data, calculations, data insertion etc. This acts as a interface between Client layer and Data Access Layer. This layer is also called the intermediary layer helps to make communication faster between client and data layer.
3) Data layer:
In this layer actual database is comes in the picture. Data Access Layer contains methods to connect with database and to perform insert, update, delete, get data from database based on our input data.

• Each layer can potentially run on a different machine.
• Presentation,Logic,Data Layers disconnected. 

Advantages

1. High performance, lightweight persistent objects
2. Scalability – Each tier can scale horizontally
3. Performance – Because the Presentation tier can cache requests, network utilization is minimized, and the load is reduced on the Application and Data tiers.
4. High degree of flexibility in deployment platform and configuration
5. Better Re-use
6. Improve Data Integrity
7. Improved Security – Client is not direct access to database.
8. Easy to maintain and modification is bit easy, won’t affect other modules
9. In three tier architecture application performance is good.

Disadvantages

1. Increase Complexity/Effort