Internet Fundamentals

Fundamental Terms Underpinning the Internet

02 What is Peering?
A Detailed Explanation of the Fundamentals of Internet Connectivity Have you ever wondered how the internet is connected?

Peering is the key to understanding the answer to this question.
In this article, we will explain peering, a little-known keyword essential for the efficient operation of the internet, in a way that is easy for beginners to understand.

What Exactly is an AS?

An AS (Autonomous System) is an independent network operated by an organization and is a unit that constitutes the internet. Each AS has its own routing policy. Various entities, such as IT companies and ISPs*1, operate ASes. Each AS is assigned a unique AS number, which identifies networks on the internet. For example, it is used to exchange routing information using BGP (Border Gateway Protocol)*2 for efficient communication on the internet.

*1 ISP (Internet Service Provider): A company that provides internet connections.
*2 BGP (Border Gateway Protocol): A routing control protocol.

What is an IX (Internet Exchange)?

Next, let’s look at IXes (Internet Exchanges), which are closely related to peering.

An IX is a platform for efficiently exchanging internet traffic. ISPs, content providers, and various other businesses’ ASes connect to an IX and engage in traffic exchange through peering. The IX serves as a hub connecting ASes, smoothing out traffic exchange, reducing internet delays, and cutting down the operational costs of ASes.

What is Peering?

Now, let's look at peering, the main topic of this article.

Peering is a form of connection where ASes on the internet directly connect and mutually exchange traffic. There are two types of peering: private peering, where specific ASes peer with each other, and public peering, where multiple ASes peer through an IX.

Private Peering

Private peering is a method where ISPs and content companies connect their networks directly. Each business prepares a dedicated line and shares IP addresses and routing information. Private peering operates on an agreement between both businesses, offering flexibility in policy and cost. However, a downside is the increased cost and management of connection lines as the number of peering partners grows.

Public Peering

Public peering is a method where multiple ISPs and content companies connect through an IX. This allows efficient peering with various networks by simply connecting to an IX. Although there is a fee for using the IX, the peering conducted over it is typically free of charge.

Other Connection Forms - Transit

In addition to peering, there is another form of network connection called transit, which we will also touch upon.
Transit is a form of connection where an AS with a large amount of route information on the internet provides this information to another AS. Typically, large-scale providers offer paid connection services to smaller providers through transit. Transit allows access to a wide range of route information but tends to be more expensive than peering.

The Benefits of Peering Through an IX

To deepen our understanding, let's look at the benefits of public peering in more detail.

Improvement in Communication Speed

Peering on an IX can lead to improved communication speeds. ASes that engage in peering also exchange routing information with each other using the BGP protocol, transferring data through optimal routes. This helps avoid unnecessary detours in internet traffic, reducing delays.

In an era where services like streaming, online gaming, and financial transactions cannot afford even slight delays, such speed improvements contribute significantly to the quality of internet services.

Reduction in Communication Costs

Smaller businesses only have route information within their AS. They can communicate globally by obtaining route information from other ISPs and content companies through paid transit services offered by large ISPs. However, this method can become costly.
Peering through an IX allows for the free exchange of route information with many companies at once, greatly reducing communication costs.


The internet is a collection of countless networks, and one of the ways these networks connect with each other is through peering. As the number of networks continues to grow and evolve, how they peer is constantly under review and updated. Peering, including public peering through an IX, is a key element in keeping the internet a comfortable and efficient space.