Tier 1 networks
A Tier 1 network can reach every network on the Internet without paying anyone for transit. It exchanges traffic with the other Tier 1 networks through settlement-free peering and sells transit to almost everyone else.
The list
These are the networks BGP Map treats as transit-free. On every map they are violet and marked T1. Open one to see the prefixes it announces and a map of its largest one.
| AS number | Registered name |
|---|---|
| AS174 | COGENT-174 - Cogent Communications, LLC |
| AS701 | UUNET - Verizon Business |
| AS1239 | COGENT-1239 - Cogent Communications, LLC |
| AS1299 | TWELVE99 Arelion Sweden AB |
| AS2914 | NTT-DATA-2914 - NTT America, Inc. |
| AS3257 | GTT-BACKBONE GTT Communications Inc. |
| AS3320 | DTAG Deutsche Telekom AG |
| AS3356 | LEVEL3 - Level 3 Parent, LLC |
| AS3491 | PCCWG-APAC-HK - PCCW Global (HK) Ltd. |
| AS5511 | Opentransit Orange S.A. |
| AS6453 | AS6453 - TATA COMMUNICATIONS (AMERICA) INC |
| AS6461 | ZAYO-6461 - Zayo Bandwidth |
| AS6762 | SEABONE-NET TELECOM ITALIA SPARKLE S.p.A. |
| AS6830 | LibertyGlobal Liberty Global Europe Holding B.V. |
| AS7018 | ATT-INTERNET4 - AT&T Enterprises, LLC |
| AS12956 | TELXIUS TELEFONICA GLOBAL SOLUTIONS SL |
Names as registered, from the RIPE NCC's list of AS names.
How transit-free is worked out
No registry hands out Tier 1 status, and peering contracts are private. People who keep these lists infer it from routing data instead. If a network shows up in paths as a peer of the other large networks and as a provider to others, and never behind a provider of its own, it counts as transit-free. Public route collectors such as RIPE RIS are where most of that evidence comes from.
Why the lists disagree
The group changes slowly, but it does change. Backbones are sold and merged, and a network drops out once it starts buying transit, even in one region. Some networks are transit-free for IPv4 and not for IPv6, which puts them on one list and off another.
Peering disputes matter too. When two large networks stop peering, customers that depend on only one of them can lose the ability to reach some of the other network's customers until the dispute is settled. Any Tier 1 list, this one included, is a snapshot. The paths on a map show what actually happens for a given prefix, whatever label a network carries.
Tier 2 and the other colours
Blue boxes marked T2 are large national and international transit networks that buy transit somewhere or do not peer with every Tier 1 network. There is no public definition of Tier 2 either, so that list is kept by hand. Any other network that carries someone else's routes on a particular map is cyan, and networks that only pass on their own routes are white.
A Tier 1 network is not automatically the best provider to buy from. What matters for a customer is where the provider has capacity, how it treats congestion and how well it peers in the regions that customer's users are in. Finding a network's upstream providers shows how to see who a network actually uses.
More guides
- How to read a BGP mapWhat the boxes, arrows, numbers and colours on a map mean.
- How to find the upstream providers of a networkReading transit providers from AS paths, and what the shares mean.
- Which network announces an IP address?From an address to its prefix and origin AS, and when whois disagrees.
- What is an AS path?How the AS path is written and used, and what prepending does.