On Thu, Feb 14, 2008 at 11:02:54AM -0600, Kai Chen wrote:
A typical Internet Exchange Point (IXP) consists of one or more network switches <http://en.wikipedia.org/wiki/Network_switch>, to which each of the participating ISPs connect. We call it the exchange-based topology. My question is if some current IXPs use directly-connected topology, in which ISPs just connect to each other by direct link, not through a network switch?? If so, what's the percentage of this directly-connected case?
Kai
the "directly-connected" case - over point2point link is not per se, an Internet Exchange Point (IXP) in that there is no chance of multiplexing the link to connect more than one provider over that direct link. the direct link can be a dedicated fiber pair, a cat5 cable, conditioned copper pair or coax or combination of these layer one transmission media (yeah, sat, microwave, avian carrier etc...) depending on proximity and cost. latency is usually less of an issue here, as is buffering, since there is a single endpoint. Its also much easier to maintain security associations on direct links. --bill