Tier 1 and Tier 2 Networks — The Internet Backbone Hierarchy
The internet isn’t one network. It’s tens of thousands of independently operated networks stitched together by BGP (Border Gateway Protocol). These networks fall into a loose hierarchy.
The Three Tiers
Tier 1 — The Backbone
A Tier 1 network can reach every other network on the internet without paying anyone for transit. They achieve this through settlement-free peering agreements with other Tier 1s — mutual handshakes where no money changes hands.
The recognized global Tier 1s (as of 2026):
| Network | ASN | Headquarters |
|---|---|---|
| Lumen (formerly CenturyLink/Level 3) | AS3356 | USA |
| Cogent Communications | AS174 | USA |
| NTT Communications | AS2914 | Japan |
| Telia Carrier (now Arelion) | AS1299 | Sweden |
| GTT Communications | AS3257 | USA |
| AT&T | AS7018 | USA |
| Verizon | AS701 | USA |
| Zayo | AS6461 | USA |
| PCCW Global | AS3491 | Hong Kong |
| Hurricane Electric | AS6939 | USA |
| Deutsche Telekom | AS3320 | Germany |
| Telecom Italia Sparkle | AS6762 | Italy |
There are about 8-15 depending on who you ask. The exact list is debated because peering relationships shift over time.
A fully meshed backbone. Each Tier 1 connects directly to every other Tier 1 so traffic can flow without intermediaries.
Tier 2 — Where Your ISP Lives
Tier 2 networks peer with some networks for free but pay Tier 1s for transit to reach parts of the internet they can’t access directly.
Singtel (AS7473), StarHub (AS4657), M1 (AS4773), and Simba (AS4817) are all Tier 2. The difference is scale:
| ISP | ASN | IPv4 Prefixes | Peers | Traffic |
|---|---|---|---|---|
| Singtel | AS7473 | ~100,000 | 253 | Not disclosed |
| StarHub | AS4657 | ~5,000 | Moderate | ~200-300 Gbps |
| M1 | AS4773 | ~500 | ~100G at SGIX | Not disclosed |
| Simba | AS4817 | ~40 | Limited | ~100-200 Gbps |
Tier 3 — Pure Resellers
Tier 3 networks own no infrastructure. They buy transit from Tier 2 or Tier 1 providers and resell it to end users. Some of the smallest MVNOs operate this way.
Why Tier Matters
A Tier 1 network has: - Global reach without middlemen (fewer hops) - Massive capital investment in physical fibre - Redundancy across multiple routes - Direct peering with content providers (Netflix, Google, etc.)
A small Tier 2 like Simba has: - Fewer direct routes (traffic takes more hops) - Higher oversubscription (more customers sharing less capacity) - Dependence on upstream providers working correctly
When a submarine cable breaks, Tier 1 networks reroute instantly through their mesh. A small Tier 2 that buys transit from that Tier 1 is at the mercy of that upstream provider’s rerouting speed.
The Reality
For browsing YouTube and Instagram from Singapore, Tier 1 vs Tier 2 makes zero difference. Content is cached locally (Google has servers in Singapore). Your latency is 4ms either way.
The tier distinction matters for: - Niche international routes (game servers in South America) - Network resilience during outages - Business/enterprise connectivity where SLAs matter - Understanding why some ISPs are more expensive