The definition of a 'Tier 1' IP network is the most hotly disputed term in internetworking, largely because all carriers want to be one. If any page on this wiki generates an edit war, this will be the page. :-)
In short, a Tier 1 network has 2 main defining characteristics:
- It buys no transit, peering with any other networks with which it interconnects, nearly always in a settlement-free manner, and
- It participates in the default-free zone.