Comment Re:sell is the key word. Cogent not paying Verizon (Score 1) 289
Shortest exit path routing.
It's pretty much what everyone's expected to do and makes technical sense: you don't know the topology of the other guy's network, so if you have a packet for one of his customers, you should hand it over to that network at the closest possible point, rather than hauling it over your backbone and possibly having the other guy haul it back if your assumptions about costs are wrong..
But this means people that are "push" heavy use a lot less backbone resources than the provider that is receiving the traffic. Historically that has resulted in payments when peering connections have significantly asymmetric traffic flows.