W H I T E P A P E R
T i e r 1 I S P s : W h a t T h e y A r e a n d W h y T h e y A r e I m p o r t a n t Sponsored by: NTT Communications
Mark Winther May 2006
E X E C U T I V E S U MMARY
The global Internet is an amalgam of separate, but semiautonomous networks. The binding element of the global Internet is that networks share a common IP addressing and global BGP routing framework. Generally, smaller tier 2 and 3 Internet service providers (ISPs) connect to larger tier 1 networks for delivery of their customers' packets to destinations outside the smaller providers' footprints.
The choice of which network to connect to for upstream bandwidth is important because it affects the experience of end-user customers. Many networks refer to themselves as tier 1 ISPs, but their specific capabilities often vary widely and attributes may vary.
The simple approach has been to label a network tier 1 if it has large traffic volumes, large capacities, large customer bases, and large numbers of routes and if it supports many autonomous systems (ASs) inside the network.
However, size and scale are not the only dimensions of tier 1 ISPs. The key attributes of tier 1 ISPs are as follows: