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What is a Transit Provider?

A transit provider is an internet service provider (ISP) that sells access to the global internet by allowing another network’s traffic to pass through its infrastructure.

In practice, a transit provider enables organizations, such as other ISPs, enterprises, or data centers, to reach all other networks on the internet, not just a limited set of direct connections. This is typically a paid, wholesale service, where the customer relies on the provider’s network to route data worldwide.

Transit providers operate within the internet’s tiered hierarchy, which reflects how networks interconnect:

  • Tier 1 providers sit at the top of the hierarchy. They form the global internet backbone and can reach every network without purchasing transit, relying instead on settlement-free peering with one another.
  • Tier 2 providers both buy and sell transit, combining paid upstream access with selective peering.
  • Tier 3 providers (often local ISPs) primarily purchase transit to deliver internet access to end users.

Most transit services are delivered by Tier 1 and large Tier 2 providers, which act as upstream networks for smaller providers.

Well-known global transit providers include companies such as AT&T, Verizon, NTT, Lumen Technologies, Cogent Communications, Arelion, and Tata Communications. All operate large-scale backbone networks and provide transit services globally.