Decentralized network coordinate systems promise efficient network distance estimates across Internet endhosts. These systems support a wide range of network services, including proximity-based routing, neighbor selection in overlays, network-aware overlays, and replica placement in content-distribution networks. This paper describes Veracity, a practical fullydecentralized service for securing network coordinate systems. In Veracity, all advertised coordinates and subsequent coordinate updates must be independently verified by a small set of nodes via a voting scheme. Unlike existing approaches, Veracity does not require any a priori secrets or trusted parties, and does not depend on outlier analysis of coordinates based on a fixed set of neighbors. We have implemented Veracity by modifying an open-source network coordinate system, and have demonstrated within a simulated network environment and deployment on PlanetLab that Veracity mitigates attacks for moderate sizes of malicious nodes (up to 30% of the network), even when coalitions of attackers coordinate their attacks. We further show that Veracity resists high levels of churn and incurs only a modest communication overhead.

Network coordinates can be used in large-scale overlay applications to reduce the cost of latency estimation. Previous proposals assumed that all nodes for which latencies were to be estimated actively participated in measurement and computation of network coordinates. In this paper, we introduce proxy network coordinates, a method that enables an overlay network to calculate network coordinates for external nodes without their direct involvement. We describe an algorithm for maintaining proxy network coordinates and show that their accuracy and stability properties are comparable to directlymaintained network coordinates.

To scale to millions of Internet users with good performance, content delivery networks (CDNs) must balance requests between content servers while assigning clients to nearby servers. In this paper, we describe a new CDN design that associates synthetic load-aware coordinates with clients and content servers and uses them to direct content requests to cached content. This approach helps achieve good performance when request workloads and resource availability in the CDN are dynamic. A deployment and evaluation of our system on PlanetLab demonstrates how it achieves low request times with high cache hit ratios when compared to other CDN approaches. 1.

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The Internet has been designed as a best-effort communication medium between its users, providing connectivity but optimizing little else. It does not guarantee good paths between two users: packets may take longer or more congested routes than necessary, they may be delayed by slow reaction to failures, there may even be no path between users. To obtain better paths, users can form routing overlay networks, which improve the performance of packet delivery by forwarding packets along links in self-constructed graphs. Routing overlays delegate the task of selecting paths to users, who can choose among a diversity of routes which are more reliable, less loaded, shorter or have higher bandwidth than those chosen by the underlying infrastructure. Although they offer improved communication performance, existing routing overlay networks are neither scalable nor fair: the cost of measuring and computing path performance metrics between participants is high (which limits the number of participants) and they lack robustness to misbehavior and selfishness (which could discourage the participation of nodes that are morelikely to offer than to receive service). In this dissertation, I focus on finding low-latency paths using routing overlay

The increasing prominence of the Internet, the Web, and large data-networks in general has profoundly affected social and commercial activity. It has also wrought one of the most profound shifts in Computer Science since its inception. Traditionally, Computer-Science research focused primarily on understanding how best to design, build, analyze, and program computers. Research focus has now shifted to the question of how best to design, build, analyze, and operate networks. How can one ensure that a network created and used by many autonomous organizations and individuals functions properly, respects the rights of users, and exploits its vast shared resources fully and fairly? The Theory of Computation (ToC) community can help address the full spectrum of research questions implicit in this grand challenge by developing a Theory of Networked Computation (ToNC), encompassing both positive and negative results. ToC research has already evolved with and influenced the growth of the Web, producing interesting results and techniques in diverse problem domains, including search and information retrieval, network protocols, error correction, Internet-based auctions, and security. A more general Theory of Networked Computation could influence the development of new

Handling node churn in decentralised network

Abstract—This paper presents a design for a general locality preserving routing overlay network based on geographic coordinates of nodes. For efficient use of network resources, it is important to follow some locality principles while routing bulk multimedia content. The proposed overlay network creates the interconnection among large number of highly dynamic nodes in a completely decentralized manner, based on adaptive hierarchical partitioning of the geographical space. A major benefit of using coarse grain geographic coordinates is that they are available at off-the-shelf databases and thus do not incur additional measurement overhead. The performance of the proposed geography based routing overlay, in terms of two locality properties – stretch and route-convergence, is evaluated by simulation studies. Real topology data of 65 ISPs with presence in 534 cities across the world, collected by the RocketFuel project, is used as the basis of the simulated network. The performance results are compared with corresponding results obtained from a simulated Pastry overlay constructed on the same underlying network. The performance results show that proposed overlay has significantly better stretch and route-convergence characteristics compared to a regular Pastry network. The locality properties of the proposed routing overlay are almost equivalent to those of an optimal Pastry network where all nodes use the most proximal neighbor for each routing table row. Thus the proposed geographical routing network provides good locality properties without the overhead of proximity neighbor selection. Moreover, the proposed scheme facilitates certain geographical search applications that are difficult to realize in a Pastry overlay. I.

One of the most flexible features of Internet routing—that service providers have administrative autonomy over their networks—has, over the years, proven to be one of the most restrictive—users have little to no say in how their packets are

The increasing prominence of the Internet, the Web, and large data networks in general has profoundly affected social and commercial activity. It has also wrought one of the most profound changes in Computer Science since its inception. Traditionally, Computer-Science research has focused primarily on understanding how best to design, build, analyze, and program computers. The research agenda has now expanded to include the question of how best to design, build, analyze, and operate networks. How can one ensure that a network created and used by many autonomous organizations and individuals functions properly, respects the rights of users, and exploits its vast shared resources fully and fairly? The Theory of Computation (ToC) community can help address the full spectrum of research questions implicit in this grand challenge by developing a Theory of Networked Computation (ToNC), encompassing both positive and negative results. ToC research has already evolved with and influenced the growth of the Web, producing interesting results and techniques in diverse problem domains, including search and information retrieval, network protocols, error correction, Internet-based auctions, and security.