N-tier applications separate an application into logical layers or tiers for increased maintainability and scalability. This includes a presentation tier for user interfaces, a middle tier for business logic and data access, and a data tier for data storage. Separating an application into tiers allows individual tiers to be updated or scaled independently without redesigning the entire application. A typical n-tier application implementation uses separate projects or services for each tier.

1. Microsoft .NET
Muhammad Ghalib Mirza
.NET Application
Development

2. N-tier data applications are applications that access data and are separated
into multiple logical layers, or tiers. Separating application components into
discrete tiers increases the maintainability and scalability of the application. It
does this by enabling easier adoption of new technologies that can be
applied to a single tier without requiring you to redesign the whole solution.
N-tier architecture includes a presentation tier, a middle-tier, and a data tier.
The middle tier typically includes a data access layer, a business logic layer,
and shared components such as authentication and validation. The data tier
includes a relational database. N-tier applications usually store sensitive
information in the data access layer of the middle-tier to maintain isolation
from end users who access the presentation tier.

3. A typical n-tier application includes a presentation tier, a middle tier, and a data
tier. The easiest way to separate the various tiers in an n-tier application is to
create discrete projects for each tier that you want to include in your
application. For example, the presentation tier might be a Windows Forms
application, whereas the data access logic might be a class library located in
the middle tier.
Here I consider a 3 Layered application Design. These 3-Layes are:
 Presentation Layer.
 Middle Layer.
 Business Rules.
 Data Validations.
 Authorization/Authentications.
 Data Access Layer.

4. This is the top most layer of application where user performs their activity.
Let’s take example of any application where user needs to fill up one form.
This form is nothing nut presentation layer. In windows application windows
form is presentation layer and in web application web form belongs to
presentation layer. Basically user’s input validation and rule processing
performs in this layer.
This is on top of presentation layer. As the name suggest, most of the
business operation performs here. For example, after collecting form data
we want to validate them with our custom business rule. Basically we define
classes and business entities in this layer.

5. It is on top of Business Logic Layer Data Access Layer presents. It
contains methods that helps business layer to connect with database
and perform CRUD operation. In data access layer generally all
database related code and stuff belongs to. Sometimes people use
platform independent data access layer to fetch data from different
database vendor.

6. The three tier design is the one of the most common best practice design
and this is so common that most of the software developers are familiar
with the acronym DAL and BAL used to refer to the data access layer and
business access layer respectively.
Now look how the application evolves into these tiers.
Case # 1

7. Case #2

10. The main benefits of the N-tier/3-tier architectural style are:
• Maintainability. Because each tier is independent of the other
tiers, updates or changes can be carried out without affecting
the application as a whole.
• Scalability. Because tiers are based on the deployment of
layers, scaling out an application is reasonably straightforward.
• Flexibility. Because each tier can be managed or scaled
independently, flexibility is increased.
• Availability. Applications can exploit the modular architecture
of enabling systems using easily scalable components, which
increases availability.

11. • The performance of the whole application may be slow if the
hardware and network bandwidth aren’t good enough because
more networks, computers and processes are involved.
• More cost for hardware, network, maintenance and deployment
because more hardware and better network bandwidth are
needed.

12. An N-Tier design can refer to logical and physical separation of
responsibilities within an application. The terms tiers and layers
may be used interchangeably though each has specific meaning
as well. Logical separation in two layers can improve the code
maintainability while physical separation into tiers can provide
scalability, security and fault tolerance among other benefits.
Applications can evolve over the time as their needs require the
complexity of an N-Tier design.