Revisiting the interplay of inter-domain traffic and routing policies
Thomas Krenc · DepositOnce · 2019
The Internet started out – with the inception of ARPANET in the 1960s, followed by NSFNET in 1986 – as a government-funded academic research network interconnecting universities and research facilities. Just a few years later, the World Wide Web was invented, and the first commercial service providers emerged. During the transition phase from a research to a commercial-purpose network, most of the crucial changes to protocols, infrastructure, and governance have occurred and continue to shape the Internet today. In its current state, the Internet is a collection of tens of thousands interconnected networks which exchange traffic among each other. These heterogeneous networks, varying in size and type, are owned and operated by organizations with individual interests and goals. While some networks provide connectivity to consumers and companies, other networks focus on the distribution and delivery of content. Depending on their business model, traffic composition and volumes exchanged among these networks can vary significantly. Network operators need to understand the composition of traffic in order to meet the quality expectations of their customers. However, Internet traffic is more diverse than ever. Many different applications, including video streaming, gaming, or file-sharing, dominate the dynamic composition of traffic, while live events such as the World Cup cause major temporal variations in traffic volume. Moreover, an increasing trend towards traffic encryption makes it increasingly difficult for network operators to obtain a holistic picture of the traffic landscape. Further, the manner in which traffic is exchanged between the networks makes it increasingly hard to reason about trends in the Internet. The exchange of traffic is governed by complex business relations among ISPs, or by traffic steering policies performed by CDNs and cloud providers who take advantage of network and path diversity by peering at IXPs. Inter-domain routing and the associated traffic flow is steadily evolving. In order to keep track of developments in the Internet, it is vital to steadily revisit changes to infrastructure and policies and how they affect traffic flow. In this dissertation, we investigate the traffic flow and the underlying routing mechanisms. Specifically, we seek to gain a better understanding of heterogeneity and traffic asymmetries on inter-domain links and the global routing table growth. We dissect the composition of today’s Internet traffic and the interactions of the involved parties and highlight the economic incentives that drive many of the main commercial players to deploy their servers deep within third-party networks. Further, we illuminate how hypergiants and complex business relationships impact the balance and distribution of ingress and egress in inter-domain traffic. Finally, we study the ramifications of these complexities on the global routing table growth by investigating one of the contributors to growth, namely prefix delegations, and how different parties use prefix delegations to influence path selection. Through the analysis of the Internet from multiple points of view, we observe an increasing trend towards network heterogeneity and unconventional routing, which is increasingly diverging from our notion of a hierarchical Internet. Our findings contribute to advancing a new mental model for the Internet’s ecosystem that goes beyond traffic agnostic AS-graph models and can support network operators in network planning and provisioning. Last, insights in the complexities of prefix delegations shed light on current protocol limitations and can inform protocol designers in the future.