On 23 December 2015 at 20:05, Reza Motamedi <motamedi@cs.uoregon.edu> wrote:
In Private peering however the AS pays the colo provider for the xconnect per ASes that it wants to peer with. The cost of transit would be additional if the peering is in fact a transit and not settlement free.
You are still assuming there is a colo. But perhaps the most common case is a multihomed company buying transit from two independent service providers. The customer is at his office and the two service providers will have their end somewhere in the city, perhaps even terminating their end of the circuit in a street cabinet. The customer is multihomed and therefore has his own AS. This is a peering situation with three AS numbers that fits your description, it is private peering and there is no xconnect. Instead there is usually a leased line cost, but this cost is often hidden from the customer. Also the ISP might own the line (physical fiber) and the cost is not a simple $/month. But also two ISPs might peer in this way. Residual internet providers have a ton of points of presences, so why choose a place where there is a xconnect fee? We can peer anywhere in the city, including at a random street cabinet. Often the cost of renting a dark fiber somewhere is lower than a xconnect fee (a sign that datacenter owners are too greedy). If one party is a content provider I give you that the peering point is usually at a datacenter somewhere. But still, if the content provider is big enough to run their own datacenter, we are back at the leased line case again. Some content providers, even if small, prefer to just run their own datacenter in the basement of their offices. Regards, Baldur