On Tue, May 02, 2006 at 10:38:22PM -0700, Robert Sherrard wrote:
  

What make a provider a tier 2, versus a tier 1 provider...

Is it possible to determine who a tier 2 (i.e. Cogent) leases fiber from?
    

It has absolutely nothing to do with fiber.

http://en.wikipedia.org/wiki/Tier_1_carrier

As of this exact moment that I'm posting, that article is actually 
reasonably accurate. Of course I'm sure in 5 minutes 100 people will be 
updating it to include their favorite not-really-a-tier-1 carrier. :)