1. Introduction
In this tutorial, we’re going to go over the N-tier architecture in software development. To start, we’ll give a definition, we’ll review its components, and outline its characteristics. Then, we’ll also describe the benefits and drawbacks, and give examples of situations where they are appropriate for use.
2. What Is A N-tier Architecture?
Before we look at N-tier architectures, software architecture is the basic structure of any software system and incorporates any aspect that makes a system function and behaves as it should. There are different software architectures in use to dates such as client-servers, microservices, microkernels, and layered architectures.
Now, an N-tier architecture is a multilayered client-server architecture in which the presentation, processing, and data functions are divided into logically and physically separate tiers. Being physically separated also means that each of these functions executes on different physical machines. Sometimes in different geographical locations.
Let’s take a look at some key characteristics.
2.1. Characteristics
N-tier architectures are usually connected in a linear narrative, that is to say, we must pass through one tier to get to the next.
Furthermore, despite the physical and logical separation of components, an N-tier application appears and functions as a single unit to the user. This is an example of distributed networking. The different components usually communicate through communication links such as high-speed buses.
Additionally, N-tier architectures also adopt a client-server model. In the client-server model, multiple clients request and receive service from a centralized server. In this case, the client and server are both computer programs running in different tiers.
Lastly, N-tier also means that the architecture can have an arbitrary number of tiers, however, 3-tier is the most common. FOr example, in 1-tier architecture, all components would be placed on a single-tier hence a single machine.
3. Components of a Layered Architecture
The N-tier architecture divides its main components into logically and physically separate components. These are the presentation tier, processing or logic tier, and data tier:
The presentation tier is responsible for presenting information in a format that can be easily understood and manipulated by the user. For example, a user interacting with a web application on a laptop is the presentation tier at work.
Additionally, the logic tier handles all processing functions which includes command executions, handing of errors, calculations, and any logical decisions. In the example of a web application, the logic tier would have the underlying program that renders the web pages written in a programming language such as HTML or PHP.
Lastly, the data tier handles the data store, usually a database, and any communication to and from the database. In the example of a web application, the data tier would be the database running SQL statements.
Let’s now take a look at a real use-case of N-tier architecture.
4. Example of N-tier Architecture
Let’s consider a web-based patient appointment application for a medical center, which enables patients to schedule appointments with doctors and specialists:
The presentation layer consists of the user interacting with a web browser on a computing device such as a laptop or phone. The user logs into the system with their login details and selects the doctor with whom they would like to make an appointment.
It is important to note that one of the perks of using the n-tier design is being able to change one layer easily without touching the others. In this case, the graphical interface of the web browser can be adjusted to work on different computing devices such as laptops or phones, without affecting the other tiers.
The logic tier connects to the presentation tier and consists of user authorization processes. In addition, there are scheduling and validation forms on a web server hosted on a different machine.
Lastly, the logic tier connects to the data tier and consists of a MySQL database hosted on another machine. The database hosts the details of patients, doctors, and specialists. It also contains information on available times for each of the doctors and specialists. Here, the appointment scheduled by the user is also saved on the database.
5. Benefits
Scalability is significantly improved when an N-tier architecture is used. Due to the separation of individual components in the architecture, it is easy to upgrade one component without affecting the performance or operation of the other components. For example, if storage runs low on the database in the data tier, the storage size can be increased easily and this will not affect the presentation and logic tiers.
In addition to scalability, having separate components makes it easier to maintain each of these components in the architecture without affecting the performance of all the others.
Another notable benefit of adopting this architecture is reusability. This is due to the logical separation of components which allows the architecture to be reused for different applications or projects.
Security is also heightened in an N-tier architecture because the different tiers can be secured with the appropriate security privileges as required.
6. Drawbacks
There is always the possibility of an increase in latency due to the physical separation of components. However, this is where a fast communication link would somehow solve the problem.
Additionally, an increase in the number of tiers tends to increase the complexity of the architecture. More tiers usually mean there are additional components to maintain and operate.
7. When To Use N-Tier Architectures
N-tier architectures are suitable for situations where the communication links are very fast in terms of transmitting and receiving information. This is vital because the communication links are what enable the communication between the different components.
Furthermore, this architecture is mostly suitable for applications where scalability, security, ease of maintenance, and reusability are a priority.
8. Conclusion
In this article, we’ve reviewed N-tier architectures. First, we defined software architectured and N-tier architecture. Secondly, we listed some characteristics and listed the basic components of the architecture. We also went over the benefits and drawbacks associated with this architecture. Lastly, we discussed situations where it is plausible to use the N-tier architecture.