untangling_the_web

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Heathrow airports. Internet Exchanges (IX) are also known less frequently
Network Access Points or NAPs.
as
The IX system is extremely important because it greatly facilitates the movement of
Internet traffic both within a country and around the world. IXs permit traffic to be
handed off directly between two different Autonomous Systems without incurring a
cost instead of having to travel through third party networks, which is usually slower
and more expensive. Over the past decade, there has been a marked increase in
the number of IXs in the world. It used to be the case that in order for Internet traffic
to travel within a country, it had to be routed to an Internet Exchange on another
continent because there was no way for a network in one city to get its traffic directly
to a network in another city in the same country, at least without paying a rather
steep price to use a third party network.
Internet Exchanges principally consist of a large number of switches, network
devices that select a path for sending data to its next stop. In general, a switch is
simpler than a router because it does not require as much information about the
network and routing policies.
Some IXs are relatively small while others, such as MAE-East and MAE-West in the
US, may have many providers as members and many different locations. At the
heart of this system, in which traffic is voluntarily handed off or exchanged among
Autonomous Systems, is something called peering.
Peering
"Peering is the practice of voluntarily interconnecting distinctly separate data
networks on the Internet, for the purposes of exchanging traffic between the
customers of the peered networks... Peering usually indicates that neither party pays
the other for the traffic being exchanged. There are, of course, examples of paid
peering.
The act of peering typically involves the following elements:
~ The physical interconnection of the networks involved.
~ The exchange of routing information, through the BGP routing protocol.
~ Commercial and contractual peering contracts or aqreements.!"
Why is peering so important? One of the original concepts behind the creation of the
Internet was the concept of global reachability, that is, every point on the Internet is
148 "Peering," Wikipedia,
(14
November 2006).
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