Re: Question on the topology of Internet Exchange Points

[bmanning () vacation karoshi com]

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