There are many business pros to N-Tier Architecture. For example, a small business can begin running all tiers on a single machine. As traffic and business increases, each tier can be expanded and moved to its own machine and then clustered. This is just one example of how N-Tier Architecture improves scalability and supports cost-efficient application building.
N-Tier model also make applications more readable and reusable. It reduces the amount of spaghetti code. Custom tag libraries and EJBs are easier to port to readable applications in well-maintained templates. Re usability multiplies developer productivity and improves application maintainability. It is an important feature in web applications.
N-Tier Architectures make application more robust because there is no single point of failure. Tiers function with relative independence. For example, if a business changes database vendors, they just have to replace the data tier and adjust the integration tier to any changes that affect it. The business logic tier and the presentation tier remain unchanged. Likewise, if the presentation layer changes, this will not affect the integration or data layer. In 3-Tier Architecture all the layers exist in one and affect each other. A developer would have to pick through the entire application code to implement any changes. Again, well-designed modules allow for applications or pieces of applications to be customized and used across modules or even projects. Reusability is particularly important in web applications.
As demonstrated N-Tier Architecture offers innovations in the standard Client-Server technology that spawned the Internet itself. It is but one of many web application frameworks. These are used to develop dynamic web sites, web applications or web services. They provide database access libraries, templates, and, as previously stated code re-use. Most web application frameworks follow the Model View Controller (MVC) which separate the user interface, the business rules and the data model. They provide authentication and authorization to provide security. This allows the web server to restrict user access based on pre-determined criteria. Web application frameworks also provide a unified API (Application programming Interface). This allows web application to work with various databases without requiring any code change. These frameworks also maintain a web template system.
Single layer architectures do not adapt to changes very easily. Often a minor change in technology or requirements will result in a major rewrite of large portions of the application.
Since the design is more complex than the single or two layer design, the implementation will also be more complex. When compared to pure VFP single layered design data access performance may be affected. Because of the nature of the data access mechanisms the presentation layer’s user interface design may be affected.
Creates an increased need for network traffic management, server load balancing, and fault tolerance.
Current tools are relatively immature and are more complex.
Maintenance tools are currently inadequate for maintaining server libraries. This is a potential obstacle for simplifying maintenance and promoting code reuse throughout the organization