ISP Interconnection and its Impact on Consumer Internet Performance

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What is Interconnection and Why Study It?

Interconnection is the mutual exchange of traffic across separate networks by contractual agreement between different Internet service providers (ISPs). Interconnection puts the “inter” in the Internet, joining many networks into a single system that permits one connected device to reach other connected devices, regardless of where or how they are connected. Interconnection is both definitive of the Internet, and a manifestation of a business relationship between two ISPs.

 In order to exchange traffic directly via interconnection, two ISPs physically connect in places where they both have facilities, such as in an Internet exchange point. This is usually achieved by linking short wires between routers belonging to one ISP and routers belonging to a second ISP. Making this physical connection is rarely expensive or tricky – much less so than laying new undersea cable, or digging ditches to install new fiber or other network infrastructure. The traffic that flows through interconnections is the lifeblood of the Internet – nearly all of the value of the Internet comes from the exchange of traffic across networks, even when the ISPs involved are fierce competitors. As a result, the business arrangements associated with interconnection are not inconsequential, and can be complex and hotly negotiated. Once ISPs agree on an arrangement, interconnections are typically maintained as common infrastructure between both parties. In some cases, traffic to and from more than one Access ISP may transit a single interconnection, or conversely, a given Access ISP may have multiple and distinct interconnection points with a given Transit ISP.  Further study could productively explore the differences and how they result to this scope of research. 

While interconnection has a profound impact on all aspects of Internet performance, it is nearly always implemented and visible only to ISPs and the engineers who run their networks. It’s thus both remote from consumers, literally and conceptually, and difficult to observe. Studying the way interconnection impacts network performance provides insight into the health of Internet infrastructure, and the way in which its management and maintenance directly impacts consumers. This work expands on current consumer Internet performance research, moving from a focus on the performance of Access ISPs’ edge networks to an analysis of how the Internet performs as an integrated system, including the complex business and technical relationships that shape the expectations and experience of consumers. 

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