Abstract — Topology discovery systems are starting to be introduced in the form of easily and widely deployed software. Unfortunately, the research community has not examined the problem of how to perform such measurements efficiently and in a network-friendly manner. This paper describes several contributions towards that end. These were first presented in the proceedings of ACM SIGMETRICS 2005. We show that standard topology discovery methods (e.g., skitter) are quite inefficient, repeatedly probing the same interfaces. This is a concern, because when scaled up, such methods will generate so much traffic that they will begin to resemble DDoS attacks. We propose two metrics focusing on redundancy in probing and show that both are important. We also propose and evaluate Doubletree, an algorithm that strongly reduces redundancy while maintaining nearly the same level of node and link coverage. The key ideas are to exploit the tree-like structure of routes to and from a single point in order to guide when to stop probing, and to probe each path by starting near its midpoint. Following the SIGMETRICS work, we implemented Doubletree, and deployed it in a real network environment. This paper describes that implementation, as well as preliminary favorable results. Index Terms — network topology, traceroute, cooperative algorithms. I.

Research on decentralized systems such as peer-to-peer overlays and ad hoc networks has been hampered by the fact that few systems of this type are in production use, and the space of possible applications is still poorly understood. As a consequence, new ideas have mostly been evaluated using common synthetic workloads, traces from a few existing systems, testbeds like PlanetLab, and simulators like ns-2. Some of these methods have, in fact, become the “gold standard ” for evaluating new systems, and are often a prerequisite for getting papers accepted at top conferences in the field. In this paper, we examine the current practice of evaluating decentralized systems under these specific sets of conditions and point out pitfalls associated with this practice. In particular, we argue that (i) despite authors ’ best intentions, results from such evaluations often end up being inappropriately generalized; (ii) there is an incentive not to deviate from the accepted standard of evaluation, even if that is technically appropriate; (iii) research may gravitate towards systems that are feasible and perform well when evaluated in the accepted environments; and, (iv) in the worst-case, research may become ossified as a result. We close with a call to action for the community to develop tools, data, and best practices that allow systems to be evaluated across a space of workloads and environments. 1.

(OCI-0532233), the workshop was intended to begin a discussion regarding the viability and utility of a community-oriented network measurement infrastructure. This report was published 20 December

Network-layer innovation has proven surprisingly difficult, in part because internetworking protocols ignore competing economic interests and because a few protocols dominate, enabling layer violations that entrench technologies. Many shortcomings of today’s internetwork layer result from its inflexibility with respect to the policies of the stakeholders: users and service providers. The consequences of these failings are well-known: various hacks, layering violations, and overloadings are introduced to enforce policies and attempt to get the upper hand in various “tussles”. The result is a network that is increasingly brittle, hostile to innovation, vulnerable to attack, and insensitive to concerns about accountability and privacy. Our project aims to design, implement, and evaluate through daily use a minimalist internetwork layer and auxiliary functionality that anticipates tussles and allows them to be played out in policy space, as opposed to in the packet-forwarding path. We call our approach postmodern internetwork architecture, because it is a reaction against many established network layer design concepts. The overall goal of the project is to make a larger portion of the network design space accessible without sacrificing the economy of scale offered by the unified Internet. We will use the postmodern architecture to explore basic architectural questions. These include: • What mechanisms should be supported by the network such that any foreseeable policy requirement can be

Abstract—Peer-to-peer streaming systems are becoming highly popular for IP Television (IPTV). Most systems can be categorized as either tree-based or mesh-based, and as either pushbased or pull-based. However, there is a lack of clear understanding of how these different mechanisms perform comparatively in a real-world setting. In this paper, we compare two representative streaming systems using mesh-based and multiple tree-based overlay routing through deployments on the PlanetLab widearea experimentation platform. To the best of our knowledge, this is the first study to directly compare streaming overlay architectures in real Internet settings. Our results indicate that mesh-based systems inject a much higher number of duplicate packets into the network, but they perform better under a variety of conditions. In particular, mesh-based systems give consistently higher application goodput when the number of overlay nodes, or the streaming rates increase. They also perform better under churn and large flash crowds. Their performance suffers when latencies among peers are high, however. Overall, mesh-based systems appear to be a better choice than multi-tree based systems for peer-to-peer streaming at a large scale. I.

Experimentation is an essential tool employed by the developers of software systems, especially distributed systems. In prior work we developed a model-driven framework for automating various experimentation tasks, such as workload generation, and demonstrated that it gives the engineer a cost-effective means to conduct large-scale experiments on distributed testbeds. We have enhanced the methods underlying the framework in four significant ways: (1) increasing the expressiveness of workloads by allowing for conditional and reactive behaviors; (2) supporting the repeatability of experiments through the creation of environment workloads that can control the operational context; (3) enabling the composability of application and environment workloads to obtain a broader class of experiments; and (4) extending the scope of experiment management to include control over multiple runs. We use the enhancements to conduct a series of interesting new experiments. Specifically, the enhancements allow us to manipulate a fixed-wired testbed so that it simulates a mobile-wireless environment, and to selectively and maliciously inject faults into a system. Categories andSubject Descriptors

performance modeling, performance prediction, capacity planning, system management, operational

Abstract not found

Abstract. Timing analysis poses a significant threat to anonymity systems that wish to support low-latency applications like Web browsing, instant messaging, and Voice over IP (VoIP). Research into timing analysis so far has been done through simulations or unrealistic local area networks. We developed SubRosa, an experimental platform for studying timing analysis attacks and defenses in low-latency anonymity systems. We present results of experiments on PlanetLab, a globally distributed network testbed. Our experiments validate the major conclusions, but not the detailed results, obtained by prior simulation studies. We also propose a new lightweight defense based on the principles of mix design called γ-buffering and show the limitations of this approach. Finally, motivated by our experimental results, we introduce spike analysis, a new timing analysis technique that takes advantage of unusual delays in a stream to substantially reduce errors over prior techniques. 1

Many computer systems have reached the point where the goal of resource allocation is no longer to maximize utilization; instead, when demand exceeds supply and not all needs can be met, one needs a policy to guide resource allocation decisions. One natural policy is to seek efficient usage, which allocates resources to the set of users who have the highest utility for the use of the resources. Researchers have