In this article, we will get into detail about the three-tier client-server architecture. The most common type of multi-tier architecture in distributed systems is a three-tier client-server architecture. In this architecture, the entire application is organized into three computing tiers
- Presentation tier
- Application tier
- Data-tier
The major benefit of the three tiers in client-server architecture is that these tiers are developed and maintained independently and this would not impact the other tiers in case of any modification. It allows for better performance and even more scalability in architecture can be made as with the increasing demand, more servers can be added.
Three-tier client-server architecture in a distributed system:
- Presentation Tier: It is the user interface and topmost tier in the architecture. Its purpose is to take request from the client and displays information to the client. It communicates with other tiers using a web browser as it gives output on the browser. If we talk about Web-based tiers then these are developed using languages like- HTML, CSS, JavaScript.
- Application Tier: It is the middle tier of the architecture also known as the logic tier as the information/request gathered through the presentation tier is processed in detail here. It also interacts with the server that stores the data. It processes the client’s request, formats, it and sends it back to the client. It is developed using languages like- Python, Java, PHP, etc.
- Data Tier: It is the last tier of the architecture also known as the Database Tier. It is used to store the processed information so that it can be retrieved later on when required. It consists of Database Servers like- Oracle, MySQL, DB2, etc. The communication between the Presentation Tier and Data-Tier is done using middle-tier i.e. Application Tier.
Advantages:
- Logical separation is maintained between Presentation Tier, Application Tier, and Database Tier.
- Enhancement of Performance as the task is divided on multiple machines in distributed machines and moreover, each tier is independent of other tiers.
- Increasing demand for adding more servers can also be handled in the architecture as tiers can be scaled independently.
- Developers are independent to update the technology of one tier as it would not impact the other tiers.
- Reliability is improved with the independence of the tiers as issues of one tier would not affect the other ones.
- Programmers can easily maintain the database, presentation code, and business/application logic separately. If any change is required in business/application logic then it does not impact the presentation code and codebase.
- Load is balanced as the presentation tier task is separated from the server of the data tier.
- Security is improved as the client cannot communicate directly with Database Tier. Moreover, the data is validated at Application Tier before passing to Database Tier.
- The integrity of data is maintained.
- Provision of deployment to a variety of databases rather than restraining yourself to one particular technology.
Disadvantages:
- The Presentation Tier cannot communicate directly with Database Tier.
- Complexity also increases with the increase in tiers in architecture.
- There is an increase in the number of resources as codebase, presentation code, and application code need to be maintained separately.