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The Beginner’s Guide to Interconnection

What is Interconnection?​

The Internet isn’t one single network, it’s thousands of networks all talking to each other. Interconnection is the magic that makes those conversations possible. Every time you load a website, stream a video, or play an online game, your traffic hops across different networks. How those networks decide to exchange data is what interconnection is all about.

Think of it like a transportation system:

  • Highways connect cities (Internet Exchanges).
  • Toll roads get you everywhere if you’re willing to pay (transit).
  • Driveways between neighbors let you walk next door for free (peering).

Internet Exchanges (IXs): The Marketplaces of the Internet​

An Internet Exchange (IX) is a shared platform where many networks meet to exchange traffic. Instead of building dozens of separate connections, a network can plug into an IX once and instantly reach hundreds of others.

There are different kinds of IXs:

  • Non-profit / Membership-based IXs (like AMS-IX in Amsterdam or LINX in London) are owned and governed by their members. They aim to keep costs low and decision-making democratic.
  • Commercial IXs (like Equinix IX) are run as for-profit businesses, often bundling extra services such as cloud access or DDoS protection.
  • Regional / Community IXs grow out of local efforts, ISPs, universities, or municipalities setting one up to keep local traffic local, like SIX (Seattle IX).

Why IXs matter: they save money, keep data flowing efficiently, and improve user experience. For example, streaming a video in San Francisco shouldn’t bounce all the way to New York and back, an IX helps keep it local.

Transit: The Full-Access Pass​

Transit is when one network pays another, usually larger, provider to deliver its traffic to the entire Internet.

  • Analogy: it’s like buying a full-access train ticket. No matter where you want to go, the transit provider gets you there.
  • When it’s useful: if you’re a small network or just starting out, buying transit is the fastest way to guarantee global reach.
  • The trade-off: it costs money, and the more traffic you send, the more you pay.

Peering: Direct Connections Between Networks​

Peering is when two networks agree to exchange traffic directly, often at no cost, because it benefits both sides.

  • Public Peering: happens at IXs, where one connection lets you exchange traffic with many peers.
  • Private Peering: is a direct, dedicated connection between two networks with heavy traffic needs.

Why it’s powerful: peering lowers costs and improves performance. For example, an ISP peering directly with Netflix means smoother video streams for customers and lower bandwidth bills for the ISP.

Cloud Interconnection: The Modern Twist​

Today, many companies run their services in the cloud (AWS, Azure, Google Cloud, etc etc). IXs increasingly provide cloud on-ramps, direct connections into these providers.

  • Benefit: faster, more reliable, and more secure than sending cloud traffic over the Internet.
  • Reality: cloud interconnection is now part of almost every network strategy, alongside transit and peering.

VLANs: Keeping the Lanes Separate​

At an IX, dozens or even hundreds of networks share the same physical switch. So how does each one keep its traffic separate? The answer is VLANs (Virtual Local Area Networks).

  • Analogy: imagine a multi-lane highway where each lane is reserved for different types of traffic.
  • At IXs: VLANs separate peering traffic, route server sessions, and sometimes private interconnects, all on the same physical infrastructure.
  • Takeaway: VLANs make shared infrastructure safe, orderly, and efficient.

Other Useful Concepts​

  • Route Servers: a special service at IXs that lets you set up one connection but reach many peers, simplifying operations.
  • Remote Peering: allows a network to connect to an IX without being physically present, often via a carrier.
  • Cross-Connects: private physical links in data centers that support direct peering or cloud interconnects.
  • Resilience: most networks use a mix of transit, peering, and cloud interconnection to balance cost, reliability, and performance.

A Short History​

In the 1990s, transit dominated, smaller ISPs all paid large Tier-1 carriers for global connectivity. As traffic exploded, especially with the rise of web content and video, networks started peering to cut costs and improve performance. IXs, originally small community projects, grew into massive hubs: AMS-IX in Amsterdam, DE-CIX in Frankfurt, and LINX in London each now handle terabits of traffic per second.

Today, the hybrid model is the norm:

  • Transit for the long tail (global reach).
  • Peering for high-volume, high-value partners.
  • Cloud interconnects to reach the services everyone depends on.

✨Beginner's takeaway:​

  • IX = the platform (the marketplace).
  • Transit & peering = the services (the deals you strike).
  • Cloud = the modern extension.
  • VLANs = the lanes that keep it all organized.