3-Tier Network Architecture: Explained

Quick Definition: A 3-tier network architecture logically separates the end-user from the application and database servers. This provides independently scalable tiers and additional security for the back-end assets. 

When you complete a task on your computer, a lot happens behind the scenes. For example, when you visit a website, say CBTNuggets.com, you see a website with a login page and lots of great information, but your computer sees much more. 

Behind the scenes, your computer is interacting with a 3-tier network architecture to gather information about displaying the page, interacting with the page, and even interacting with databases if you’re logging into your account or working your way through one of our courses. 

In this blog, we’ll cover the basics of a 3-tier network architecture, its advantages and disadvantages, and some best practices for implementing it. 

What is the 3-Tier Network Architecture?

The 3-tier network architecture is a network setup where each layer or tier is logically separated and focused on its own task. This configuration provides three independently scalable environments, which separate the end-user from the application and database servers. 

This allows developers to improve some parts of the network stack even if other parts are not ready for upgrades. For example, you can upgrade your database servers even if your application servers can’t be upgraded at the same time due to issues like software dependencies or licensing costs. 

What are the Components of the 3-Tier Network Architecture?

The 3-tier architecture consists of a client tier (also called the presentation tier), an application tier, and a database tier. 

The Client Tier

The client tier is how you get the CBTNuggets website to appear on your screen. This tier operates via web browser or application and does so using front-end web tools like HTML, CSS, and JavaScript. This tier is all about providing you with a visual experience and providing servers with information about your device and interactions.

The Application Tier

The next tier, the application tier, is the logical middle tier that supports the functionality behind all the features you see via the client tier. This tier is usually developed in languages like Python or Java. It responds to inputs gathered from the client tier and does something with them. (What it does depends on the website's purpose or programming.) 

The Database Tier

Finally, we have the database tier (also referred to simply as the data tier). This tier is the back-end that completes the response to your input gathered from the presentation or client tier. It is where your inputs are fully processed, and any results are stored. This tier relies on MySQL, MongoDB, and other database software. 

Practical Application of 3-Tier Architecture 

All three of these tiers work together to provide you with a full user experience when browsing the web. Let’s look at this from start to finish: say you’re on the CBTNuggets page and decide to log in to your account. The client tier provides you with the page content and layout so you know where to move your cursor and click “log in.” 

The application tier takes that click and brings you to a new page where you can enter a username and password. You’re back to the client tier, where you click into the submission fields for your username and password and click the “submit” button. 

Then, the application tier takes that login attempt to the database tier, where the credentials you entered are validated against the credentials stored in the database. 

Of course, the process is a bit more complex than this, especially when you consider additional features such as multi-factor authentication, but this covers the basic concept of how 3-tier network architecture works. 

What are the Benefits of 3-Tier Network Architecture?

You may have heard about a two-tiered architecture called Spine and Leaf, which is touted as quick and scalable, so why add a tier to that? There are two major benefits to the 3-tier network architecture we’ll discuss. 

Enhanced Flexibility Through Independent Scalability

First, it’s just as scalable as the spine and leaf configuration, if not a little better. Since each tier handles a different responsibility, one tier can be scaled with little impact on the others. 

Hardware, whether physical or virtual, can also be upgraded independently between tiers. If your databases need to stay a version or three behind for some reason, you can still upgrade the rest of your stack among the client and application tiers. 

More Security with Layered Access

Another benefit to the 3-tier network architecture is better security. Your computer only interacts with the client tier, so there's a reduced likelihood of successful compromise of the application and database tiers. This is great when you consider the type of information databases might store, like passwords. 

3-Tier Network Implementation Examples

Although we briefly discussed this in an earlier section, we’ll revisit CBT Nuggets and websites as a whole since they are the perfect example of where a 3-tier network architecture makes sense. 

Your computer interacts with the web server via the client tier, which presents your computer with various web pages. The content of these web pages is made of HTML, CSS, and, more than likely, JavaScript. The client tier passes your input to the application tier, which runs on an application server. Your input is passed to the database tier for further responses. 

For example, if you were to navigate to www.cbtnuggets.com/signup to start a free 7-day trial, your request would be sent to the database tier for storage and correlation. The application tier uses other scripting and coding languages like Python, Ruby, or PHP, and runs on a framework. 

At the database tier, your information is stored in one or more databases so we can associate your login information with your name, email address, and any course information. 

The database and application tiers will interact with one another to track things like the expiration of your 7-day free trial or the completion of one or more courses. Then, that information would be passed to the client tier so the CBTNuggets webpage you see accurately reflects the information in the database server. This information would likely be stored in an SQL database or similar. 

Best Practices for Implementing 3-Tier Network Architecture

The best practices for the 3-tier network architecture are similar to the best practices of most network designs. Your client tier should have adequate load balancing capabilities to effectively distribute traffic amongst the client-facing servers. This not only helps provide a fast user experience but also helps protect your network from Distributed Denial of Service (DDoS) attacks. 

Strategically Scaling for Peak Performance

At the application tier, you should prioritize scalability. Whether you’re using a cloud service provider or hosting your own data center, you should consider configuring your application servers to autoscale resources based on increased requests. 

Some reasons an application server may see an increase in traffic include an influx of new site visitors for companies running a promotional sale or a drive for new membership sign-ups.

Securely Managing Access and Monitoring Changes

Securing connections is a best practice for servers at every tier. Configure the network to limit the number of users who have access to read and modify data and configurations on each server to only those who absolutely need access as part of their job function. 

Also, be sure to track any changes to your network and its assets, tracking items such as version information, the intent behind the change, and who made the change. 

Conclusion

A 3-tier network architecture is one which logically separates the client from the application servers and databases. The tiers involved are the client tier, application, and database, which use the application tier as an intermediary.

This setup helps reduce the risk of an attacker compromising the application and database servers since the client never directly interacts with anything other than the client-tier server. The 3-tier network architecture also allows for scalability and enhancement independent of each other, which means upgrades can be made to one tier without impacting the availability of the other tiers. 

Want to learn more about networking? Check out the CBT Nuggets course Intro to Networking.