Tier architecture Difference in asp.net

a tier is a physical seperation, and a layer is a logical seperation

so adding more layrers make it n-layered solution not a n-tiered solution.

adding so much layer may increse the complexity of your solution so try to avoid a lot of layering in the solution also.

Normally, Application divide their layers into two broad categories


1- Horizontal Layers : These layers are used to provide the application wide functionality and they can be re-used in different solutions example of layers are

a- Logging Layer b- Security Layer

2- Vertical Layers : These are the layers which actually logically creates your application e.g. UI , Business Logic , Data Access and theoratically these layers can also be used in similar applications with some changes. Horizontal layers are used across by the vertical layers.




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The "n" in n-tier basically means "a number you choose", so you could called it multiple-tier architecture. Normally, this manifests itself in three tiers. Display, Logic and Data.

This could be implemented in many different ways, as you mention - you've seen it in action where the web page has the display function, a web service has the logic function and the database satisfies the data tier.

N-Tier is an architecture, so it can be applied to any language / technology. It isn't quite a design pattern, but the principle behind it is the separation of concerns between data, logic and presentation. The difference between N-Tier architecture and a design pattern is that with N-Tier, it is describing a physical hardware separation as well as code-unit separation. A design pattern would be concerned about the code design, but not the server design.


It places constraints on the developer to limit the responsibility of the code to specific concerns in each of the layers.

i.e. :

View layer deals with making things effectively presented and validate the input and prepare it for use inside the application

Service layer will capture the "Business Rules" i.e. the logic in the reltions and transformations of the objects.

Persistence Layer will limit itself to getting data from and to long term storage, usually a database.

By limiting the responsibilities code in each layer becomes clearer and more focused and it is easier to reason about (at the expense of additional plumbing).


N-tier application architecture provides a model for developers to create a flexible and reusable application. By breaking up an application into tiers, developers only have to modify or add a specific layer, rather than have to rewrite the enitire application over, if they decide to change technologies or scale up. In the term "N-tier," "N" implies any number -- like 2-tier, or 4-tier; basically, any number of distinct tiers used in your architecture. Application architectures are part of Layer 7 of theOSI model.