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
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