  Internet eXchange Points (IXPs) are generally considered to be the successors
of the four Network Access Points that were mandated as part of the
decommissioning of the NSFNET in 1994/95 to facilitate the transition from the
NSFNET to the "public Internet" as we know it today. While this popular view
does not tell the whole story behind the early beginnings of IXPs, what is true
is that since around 1994, the number of operational IXPs worldwide has grown
to more than 300 (as of May 2013), with the largest IXPs handling daily traffic
volumes comparable to those carried by the largest Tier-1 ISPs, but IXPs have
never really attracted any attention from the networking research community. At
first glance, this lack of interest seems understandable as IXPs have
apparently little to do with current "hot" topic areas such as data centers and
cloud services or software defined networking (SDN) and mobile communication.
However, we argue in this article that, in fact, IXPs are all about data
centers and cloud services and even SDN and mobile communication and should be
of great interest to networking researchers interested in understanding the
current and future Internet ecosystem. To this end, we survey the existing but
largely unknown sources of publicly available information about IXPs to
describe their basic technical and operational aspects and highlight the
critical differences among the various IXPs in the different regions of the
world, especially in Europe and North America. More importantly, we illustrate
the important role that IXPs play in today's Internet ecosystem and discuss how
IXP-driven innovation in Europe is shaping and redefining the Internet
marketplace, not only in Europe but increasingly so around the world.
