Recently, it has been reported that certain access ISPs are surreptitiously blocking their customers from uploading data using the popular BitTorrent file-sharing protocol. The reports have sparked an intense and wide-ranging policy debate on network neutrality and ISP traffic management practices. However, to date, end users lack access to measurement tools that can detect whether their access ISPs are blocking their BitTorrent traffic. And since ISPs do not voluntarily disclose their traffic management policies, no one knows how widely BitTorrent traffic blocking is deployed in the current Internet. In this paper, we address this problem by designing an easy-to-use tool to detect BitTorrent blocking and by presenting results from a widely used public deployment of the tool.

Planetary-scale network testbeds like PlanetLab and RON have become indispensable for evaluating prototypes of distributed systems under realistic Internet conditions. However, current testbeds lack the heterogeneity that characterizes the commercial Internet. For example, most testbed nodes are connected to well-provisioned research networks, whereas most Internet nodes are in edge networks.

A large and rapidly growing proportion of users connect to the Internet via residential broadband networks such as Digital Subscriber Lines (DSL) and cable. Residential networks are often the bottleneck in the last mile of today's Internet. Their characteristics critically affect Internet applications, including voice-over-IP, online games, and peer-to-peer content sharing/delivery systems. However, to date, few studies have investigated commercial broadband deployments, and rigorous measurement data that characterize these networks at scale are lacking. In this paper, we present the first large-scale measurement study of major cable and DSL providers in North America and Europe. We describe and evaluate the measurement tools we developed for this purpose. Our study characterizes several properties of broadband networks, including link capacities, packet round-trip times and jitter, packet loss rates, queue lengths, and queue drop policies. Our analysis reveals important ways in which residential networks differ from how the Internet is conventionally thought to operate. We also discuss the implications of our findings for many emerging protocols and systems, including delay-based congestion control (e.g., PCP) and network coordinate systems (e.g., Vivaldi).

This paper proposes Monarch, a novel tool that accurately emulates transport protocol flows from an end host controlled by its user to any other Internet host that responds to simple TCP, UDP, or ICMP packet probes. Since many Internet hosts and routers respond to such probes, Monarch can evaluate transport protocols, such as TCP Reno, TCP Vegas, and TCP Nice, over a large and diverse set of Internet paths. Current approaches to evaluating these protocols need control over both end hosts of an Internet path. Consequently, they are limited to a small number of paths between nodes in testbeds like PlanetLab, RON or NIMI. Monarch's ability to evaluate transport protocols with minimal support from the destination host enables many new measurement studies. We show the feasibility of using Monarch for three example studies: (a) understanding transport protocol behavior over network paths that are less explored by the research community, such as paths to cable and DSL hosts, (b) investigating the relative performance of different transport protocol designs, such as TCP Vegas and TCP Reno, and (c) testing protocol implementations under a wide range of experimental conditions.