Is there anything the ordinary customer can do about this? I can get to level 3 but not to cogent. Does this mean I will not ever be able to access those other sites? What do you suggest we do, and how would we know which providers use what and where?
well, those questions require pretty detailed answers that i don't care to get into. suffice it to say that eventually it will be worked out by the market. for the time being, the only work around would be complex routing schemes by the carriers stuck in the middle. for those suggesting that they leave their carrier or demand that the carrier go somewhere else for service, such as roadrunner.... all i can say is that they would be shooting themselves in the foot by doing so.
as i said, i have a dog in this fight, but the best permanent solution would be for cogent to agree to a mroe equitable peering relationship and stop using other carrier's networks for a free ride, and then undercutting prices because they have no network infrastructure to pay for.
and be on the lookout; there will be lots more of this stuff coming, and not just between my company and others. this has been a brewing issue for some time now.