stuck in the middle
While we often refer to the Internet as a
single entity, it is actually composed of
13,000 different competing networks,
each providing access to some small
subset of end users. Internet capacity
has evolved over the years, shaped by
market economics. Money flows into
the networks from the first and last
miles, as companies pay for hosting
and end users pay for access. First- and
last-mile capacity has grown 20- and
50-fold, respectively, over the past five
to 10 years.
illUstration by stUdio tonne
On the other hand, the Internet’s
middle mile—made up of the peering and transit points where networks
trade traffic—is literally a no man’s
land. Here, economically, there is very
little incentive to build out capacity. If
anything, networks want to minimize
traffic coming into their networks
that they don’t get paid for. As a result, peering points are often overburdened, causing packet loss and service
degradation.
The fragile economic model of peering can have even more serious consequences. In March 2008, for example,
two major network providers, Cogent
and Telia, de-peered over a business
dispute. For more than a week, customers from Cogent lost access to Telia
and the networks connected to it, and
vice versa, meaning that Cogent and
Telia end users could not reach certain
Web sites at all.
Other reliability issues plague the
middle mile as well. Internet outages
have causes as varied as transoceanic
cable cuts, power outages, and DDoS
(distributed denial-of-service) attacks.
In February 2008, for example, communications were severely disrupted
in Southeast Asia and the Middle East
when a series of undersea cables were
cut. According to TeleGeography, the
cuts reduced bandwidth connectivity
between Europe and the Middle East
by 75%.
8
Internet protocols such as BGP
(Border Gateway Protocol, the Inter-
net’s primary internetwork routing algorithm) are just as susceptible as the
physical network infrastructure. For
example, in February 2008, when Pakistan tried to block access to You Tube
from within the country by broadcasting a more specific BGP route, it accidentally caused a near-global You Tube
blackout, underscoring the vulnerability of BGP to human error (as well as
foul play).
2
The prevalence of these Internet reliability and peering-point problems
means that the longer data must travel
through the middle mile, the more it
is subject to congestion, packet loss,
and poor performance. These middle-mile problems are further exacerbated
by current trends—most notably the
increase in last-mile capacity and demand. Broadband adoption continues
to rise, in terms of both penetration
and speed, as ISPs invest in last-mile
infrastructure. AT&T just spent approximately $6.5 billion to roll out
its U-verse service, while Verizon is
feBRuaRY 2009 | vol. 52 | No. 2 | CommunICatIons of the aCm
45
