Reducing our society's energy demand is critical to address the sustainability challenge. While the Internet currently accounts for 1–-1.5% of global electricity consumption and continues to grow, the energy demands of one of its core components---routers---remain poorly understood. The available power data is limited and not fine-grained enough, offering little actionable insight into strategies for effectively reducing the Internet's energy consumption.

With the rapid evolution and diversification of Internet applications, their communication-quality criteria are continuously evolving. To globally optimize communication quality, the Internet's control plane thus needs to optimize inter-domain paths on diverse criteria, and should provide extensibility for adding new criteria or modifying existing ones. However, current inter-domain routing protocols and proposals satisfy these requirements at best to a limited degree.

On today's Internet, end-user debugging is largely limited to simple tools such as ping and traceroute, supplemented by purpose-built services such as bandwidth measurement, and website uptime monitors. Unfortunately, these tools do not provide sufficient data to isolate specific network faults, nor do they give the user results that can be validated by external entities. Furthermore, since networks disparately treat measurement packets, as our empirical results confirm, measurement packets need to be indistinguishable from data packets. In this paper, we argue for a distributed network debugging infrastructure and describe Debuglet, a deployable and incentivized architecture that allows inter-domain network debugging using real data packets and user-defined code, which facilitates accurate and flexible measurements of the network performance experienced by data packets. We implement the Debuglet system, and demonstrate its feasibility by deploying it on a network testbed, evaluating its measurement accuracy, and analyzing its deployment costs.

Internet service providers (ISPs) have a variety of quality attributes that determine their attractiveness for data transmission, ranging from quality-of-service metrics such as jitter to security properties such as the presence of DDoS defense systems. ISPs should optimize these attributes in line with their profit objective, i.e., maximize revenue from attracted traffic while minimizing attribute-related cost, all in the context of alternative offers by competing ISPs. However, this attribute optimization is difficult not least because many aspects of ISP competition are barely understood on a systematic level, e.g., the multi-dimensional and cost-driving nature of path quality, and the distributed decision making of ISPs on the same path. In this paper, we improve this understanding by analyzing how ISP competition affects path quality and ISP profits. To that end, we develop a game-theoretic model in which ISPs (i) affect path quality via multiple attributes that entail costs, (ii) are on paths together with other selfish ISPs, and (iii) are in competition with alternative paths when attracting traffic. The model enables an extensive theoretical analysis, surprisingly showing that competition can have both positive and negative effects on path quality and ISP profits, depending on the network topology and the cost structure of ISPs. However, a large-scale simulation, which draws on real-world data to instantiate the model, shows that the positive effects will likely prevail in practice: If the number of selectable paths towards any destination increases from 1 to 5, the prevalence of quality attributes increases by at least 50%, while 75% of ISPs improve their profit.

In the face of the ever-increasing power consumption of the information and communication technology sector, next-generation Internet architectures offer an opportunity to improve the energy consumption of the Internet. The SCION architecture is unique in that it has reached commercial deployment and thus opens up opportunities for estimating and understanding the promised energy efficiency from a realistic perspective. In this work, we introduce a method that uses the available energy consumption models for the current Internet architecture to estimate the energy efficiency of SCION's data plane. By applying this method to the best available power consumption models of the Internet, we show that while providing advanced security and availability guarantees, SCION can reduce global data plane power consumption by around 700 MW. We further investigate the impact of the SCION's quality of service (QoS) extension on data plane's power consumption and conclude that SCION with its QoS extension can reduce the power consumption of the Internet by up to 2.88 GW. Therefore, SCION, with its QoS extension, reduces the power consumption of the Internet and the whole ICT sector by up to 9.4% and 1.3%, respectively.

Many critical computing applications rely on secure and dependable time which is reliably synchronized across large distributed systems. Today's time synchronization architectures are commonly based on global navigation satellite systems at the considerable risk of being exposed to outages, malfunction, or attacks against availability and accuracy. This paper describes a practical instantiation of a new global, Byzantine fault-tolerant clock synchronization approach that does not place trust in any single entity and is able to tolerate a fraction of faulty entities while still maintaining synchronization on a global scale among otherwise sovereign network topologies. Leveraging strong resilience and security properties provided by the path-aware SCION networking architecture, the presented design can be implemented as a backward compatible active standby solution for existing time synchronization deployments. Through extensive evaluation, we demonstrate that over 94 % of time servers reliably minimize the offset of their local clocks to real-time in the presence of up to 20 % malicious nodes, and all time servers remain synchronized with a skew of only 2 ms even after one year of reference clock outage.

Path aware networking (PAN) is a promising approach that enables endpoints to participate in end-to-end path selection. PAN unlocks numerous benefits, such as fast failover after link failures, application-based path selection and optimization, and native interdomain multi-path. The utility of PAN hinges on the availability of a large number of high-quality path options. In an inter-domain context, two core questions arise. Can we deploy such an architecture natively in today's Internet infrastructure without creating an overlay relying on BGP? Can we build a scalable multi-path routing system that provides a large number of high-quality paths?