Internet Fundamentals

Fundamental Terms Underpinning the Internet

05 What is an ISP (Internet Service Provider)?
A Detailed Explanation of ISP Types and Their Relationship with IXes

To use the internet, or in other words, to connect to the internet via a computer or smartphone, an ISP (Internet Service Provider) is essential. Many of you may be familiar with ISPs, but did you know there are different types of ISPs?
This article gives an overview of ISPs, their types, and their relationship to IXes in a way that's easy for beginners to understand.

What is an ISP (Internet Service Provider)?

An ISP is a business that provides services that enable individuals and companies to connect to the internet. Physical communication lines like fiber optics are not enough for internet connectivity; connection services provided by ISPs are also necessary (often, the same business provides both the line and ISP services).
When using the internet, you contract with an ISP and connect to other networks on the internet via the network of your contracted ISP. Besides providing internet connectivity, ISPs offer additional services and maintain network security.

The internet is a collection of networks interconnected globally. Since communication doesn't happen entirely within the network of a single ISP, ISPs play a role in sending and receiving user data along appropriate paths to other networks and sites.
In reality, there are different types of ISPs, known as Tier 1, Tier 2, and Tier 3. Below, we'll explain how they are differentiated.

Tier 1

Tier 1 ISPs operate global-scale internet backbones and are among the top-tier ISPs in the world. Tier 1 ISPs are directly connected to major IXes worldwide and peer with all other Tier 1 ISPs, providing access to IP addresses globally. Essentially, Tier 1 ISPs play a core role in internet infrastructure.

Tier 1 ISPs provide transit services to the lower-tier ISPs and businesses mentioned below.

Tier 2, Tier 3

Tier 2 ISPs do not own global internet backbones. Tier 2 ISPs offer connectivity to the global network by purchasing transit from Tier 1 ISPs or peering with other networks.

Tier 3 ISPs are smaller in scale than Tier 2. They provide internet connectivity services by purchasing transit from Tier 2 or peering with other networks.

Thus, Tier 1/Tier 2/Tier 3 are classifications that hierarchically categorize ISPs. It's important to note that the definitions, numbers, and relationships between these tiers are not absolute and vary by country, region, and time. Recently, hyper-scalers and big tech companies (with networks comparable to the world's top-level ISPs) have been peering with various ISPs, not confined to these tier concepts.

What is an IX (Internet Exchange)?

An IX is a platform where networks that make up the internet can efficiently exchange traffic. IXes are used not only by ISPs, which are networks on the user side but also by content providers and network service providers on the content dissemination side. By interconnecting various business networks through IXes, these networks increase traffic flow efficiency and enhance internet performance.

The Benefits of ISPs Using IXes

There are two main benefits for ISPs using IXes: improved performance and cost reduction.
When ISPs interconnect at an IX, communication routes are shortened compared to connections via transit, making traffic transfer more efficient. This can lead to faster website access and improved response of online services, providing a comfortable internet experience for end-users.
Furthermore, from a network operation perspective, ISPs can save on transit costs through peering, significantly reducing communication costs.


The internet operates through the interconnection of numerous networks, with IXes and ISPs at its core, smoothing the flow. By properly utilizing these technical mechanisms, the flow of data is optimized, and users can enjoy a faster and more stable internet environment.