Transit

The commercial internet service where one network pays another to carry its traffic to the rest of the internet, billed by bandwidth used (usually 95th-percentile).

Last updated: April 22, 2026

What is transit?

Transit is the paid service a smaller or less-connected network buys from a larger upstream provider to reach the rest of the internet. The customer pays per Mbps or Gbps, usually on a 95th-percentile model, and the transit provider announces the customer's routes out to the entire internet. Without transit, a network can only reach destinations it directly peers with.

Tier-1 transit

A "tier-1" network is one that reaches the entire internet purely through peering — it never buys transit from anyone. The list is small (roughly a dozen operators: Lumen, AT&T, NTT, Telxius, Arelion, Cogent, Zayo, and a few more) and fairly stable. Every other network, no matter how large, buys transit from at least one tier-1 or tier-2 upstream.

Transit vs. peering

Transit — commercial, carries traffic to the entire internet, paid per volume
Peering — settlement-free, carries only traffic destined for the peer and the peer's customers, no cost per volume

Most production networks use both: peer directly with the networks they exchange the most traffic with, buy transit to reach everything else. This mix is what lets BGP's "prefer shortest AS path" rule produce reasonable routes across the entire internet.

Transit in IP investigations

When investigating an IP, knowing whether an address is announced by a tier-1 carrier, a regional ISP with transit, or a niche hosting provider tells you a lot about what the IP is likely being used for. See the origin AS and its upstream transit on any IP with our WHOIS lookup tool.

Frequently Asked Questions

Almost universally on a 95th-percentile model: the provider samples your bandwidth usage in 5-minute intervals over a month, sorts the samples, drops the top 5% (~36 hours of peaks), and bills you on the highest remaining sample. This lets short bursts not blow up your bill while still capturing sustained usage. Pricing is typically dollars per Mbps per month, ranging from $0.20-$0.50 per Mbps at very high volumes down to $1-$5 per Mbps for small commitments. Some providers offer flat-rate or 95th-percentile-with-burstable-allowance hybrids.

A Tier-1 network is one that reaches every destination on the internet purely through settlement-free peering — it never pays anyone for transit. The list is small (about a dozen operators including Lumen/CenturyLink, AT&T, NTT, Telxius, Arelion/Telia, Cogent, Zayo, Tata, GTT, and a few more) and relatively stable. Every other network, no matter how large, buys transit from at least one upstream. The Tier-1 status is operationally significant — it determines who can reach the "default-free zone" without depending on any single provider.

Two reasons. Redundancy — if one transit provider has an outage or DDoS attack, traffic shifts automatically to the others via BGP. Routing optimization — different upstreams have different relationships and footprints, so for any given destination one will usually offer a shorter or less congested path than the others. BGP "best path selection" and inbound traffic engineering let networks balance cost, latency, and reliability across multiple transits.

Transit carries your traffic to the entire internet for a fee. Peering carries traffic only between you and the peer (and the peer's customers) without per-byte cost. Transit is a commercial relationship; peering is a mutual one. A complete network typically uses both — transit to reach the long tail of the internet, peering with the networks you exchange the most traffic with directly to cut costs and improve latency.

Tier-1 transit prices have collapsed by ~50% per year for decades. As of 2025, list prices for IP transit at major hubs are typically $0.20-$0.50 per Mbps/month at 10+ Gbps commit levels, $1-$3 per Mbps for sub-Gbps. Niche markets (Sub-Saharan Africa, parts of Latin America) cost 5-10x more due to limited capacity. Major content networks negotiate heavy custom discounts; commodity transit pricing is set by a handful of price-leader providers like Cogent and Hurricane Electric.

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