The Default Choice: Paying for Transit
Imagine you’re a new delivery company. To get packages to any address in the country, you could pay a national carrier like UPS or FedEx. You give them your packages, pay their fee, and they handle everything. This is IP transit. It’s a paid service where
a smaller network pays a larger network (an upstream provider) to carry its data to any destination on the global internet. For most companies and smaller Internet Service Providers (ISPs), this is the standard way to get online. It’s straightforward: you pay for access to the entire internet routing table, and the provider takes care of the rest. This provides broad reach without the complexity of building a global backbone yourself. The downside? It costs money, and you have less control over the exact path your data takes, which can sometimes mean higher latency (slower speeds) as your data bounces through other networks.
The Handshake Deal: Exchanging Traffic with Peering
Now, imagine your delivery company has grown. You notice a huge portion of your packages are going to addresses served by another large, regional delivery company. Instead of both of you paying a national carrier to exchange these local packages, you make a deal: you’ll deliver their packages in your area if they deliver yours in their area. This is peering. Two networks agree to directly exchange traffic between each other, typically for free. This is also called “settlement-free” peering because no money changes hands. The benefits are huge: it’s cheaper, faster, and gives networks more control. By cutting out the middleman (the transit provider), data travels a more direct path, which reduces latency and improves performance for users. This is often done at central locations called Internet Exchange Points (IXPs), where hundreds of networks can easily connect to each other.
So, What’s the Complication?
On the surface, it seems simple: pay for transit when you’re small, and switch to free peering when you’re big enough. The problem is that peering isn’t a right; it’s a negotiation between two parties. And the biggest networks—known as Tier 1 providers—have little incentive to peer with just anyone. A Tier 1 network is defined as a network that can reach every other network on the internet without paying for transit. They achieve this by peering with all the other Tier 1 networks. If a giant like AT&T or Lumen agrees to a free peering arrangement with a smaller ISP, they are essentially giving away a service they could be charging for. The smaller ISP gets access to the Tier 1’s massive network for free, but the Tier 1 gets very little in return, as the smaller network has far fewer unique destinations to offer.
The Power Dynamics of 'Free'
This is where the complexity lies. For a settlement-free peering agreement to make sense, it has to be mutually beneficial. This usually means the two networks must be of a similar size and exchange roughly equal amounts of traffic. If one network sends way more traffic than it receives, the other party might demand a fee (known as paid peering) or simply refuse to peer at all. These negotiations can lead to high-profile disputes. Disagreements over traffic ratios or costs have led to “de-peering” events, where two major networks abruptly sever their direct connection, sometimes disrupting internet access for millions of users who rely on those paths. While peering never fully replaces transit—as transit is still needed to reach parts of the internet you don't peer with—the strategic use of peering is what separates the internet's major players from everyone else.
