Large-scale Internet applications can benefit from an ability to predict round-trip times to other hosts without having to contact them first. Explicit measurements are often unattractive because the cost of measurement can outweigh the benefits of exploiting proximity information. Vivaldi is a simple, light-weight algorithm that assigns synthetic coordinates to hosts such that the distance between the coordinates of two hosts accurately predicts the communication latency between the hosts.

This paper addresses the problem of churn---the continuous process of node arrival and departure---in distributed hash tables (DHTs). We argue that DHTs should perform lookups quickly and consistently under churn rates at least as high as those observed in deployed P2P systems such as Kazaa. We then show through experiments on an emulated network that current DHT implementations cannot handle such churn rates. Next, we identify and explore three factors affecting DHT performance under churn: reactive versus periodic failure recovery, message timeout calculation, and proximity neighbor selection. We work in the context of a mature DHT implementation called Bamboo, using the ModelNet network emulator, which models in-network queuing, cross-traffic, and packet loss. These factors are typically missing in earlier simulationbased DHT studies, and we show that careful attention to them in Bamboo's design allows it to function effectively at churn rates at or higher than that observed in P2P file-sharing applications, while using lower maintenance bandwidth than other DHT implementations.

Vivaldi is a distributed algorithm that assigns synthetic coordinates to Internet hosts, so that the Euclidean distance between two hosts' coordinates predicts the network latency between them. Each node in Vivaldi computes its coordinates by simulating its position in a network of physical springs. Vivaldi is both distributed and efficient: no fixed infrastructure need be deployed and a new host can compute useful coordinates after collecting latency information from only a few other hosts. Vivaldi can rely on piggy-backing latency information on application traffic instead of generating extra traffic by sending its own probe packets. This paper

This thesis presents a new design and implementation of the DHash distributed hash table based on erasure encoding. This design is both more robust and more efficient than the previous replication-based implementation [15]. DHash uses

DHash is a new system that harnesses the storage and network resources of computers distributed across the Internet by providing a wide-area storage service, DHash. DHash frees applications from re-implementing mechanisms common to any system that stores data on a collection of machines: it maintains a mapping of objects to servers, replicates data for durability, and balances load across participating servers. Applications access data stored in DHash through a familiar hash-table interface: put stores data in the system under a key; get retrieves the data. DHash has proven useful to a number of application builders and has been used to build a content-distribution system [34], a Usenet replacement [118], and new Internet naming architectures [133, 132]. These applications demand low-latency, high-throughput access

This paper explains the co-ordinate based location system built for XenoSearch, a resource discovery system in the XenoServer Open Platform. The system is builds on the work of GNP, Lighthouse and many more recent schemes. We also present results from various combinations of algorithms to perform the actual co-ordinate calculation based on GNP, Lighthouse and spring based systems and show our implementations of the various algorithms give similar prediction errors. 1

Abstract- The simplicity of multicast as a communication primitive belies its broad utility as a building block for distributed applications. Nevertheless, creating and maintaining multicast structures can be challenging, particularly when networks are transient and/or dynamic. We introduce a new unstructured multi-source multicast (UMM) overlay approach that we argue is less complex than, but as efficient as, current state-of-the-art solutions based either on structured overlays or on running full routing protocols at the overlay level. UMM builds a base overlay independently from the routing mechanisms employed to route messages. On top of this base overlay, it selects distribution trees for each multicast source by first flooding the base overlay and then using the implicit information contained in duplicated messages to select and filter out redundant tunnels. Simple heuristics are used to maintain and evolve both the base overlay and the multicast distribution trees in response to changes in the set of overlay participants or in underlying network conditions. We experiment on a 65-node PlanetLab deployment and on ModelNet emulated distributed platforms to quantify the overheads associated with UMM operation and to explore its performance and adaptability to changes in the underlying network conditions. I.

This paper addresses the problem of churn---the continuous process of node arrival and departure---in distributed hash tables (DHTs). We demonstrate through experiment that existing DHT implementations break down at churn levels observed in deployed peer-to-peer systems, contrary to simulation-based results. We present Bamboo, a DHT that handles high levels of churn, and discuss the manner in which it does so. We show that Bamboo is able to function effectively for median node session times as short as 1.4 minutes, while using less than 900 bytes/s/node of maintenance bandwidth in a 1000-node system. This churn rate is faster than that observed in real file-sharing systems such as Gnutella, Kazaa, Napster, and Overnet. Since Bamboo's bandwidth usage scales logarithmically in the number of nodes, we expect this cost to remain within the reach of dialup modems even for very large systems. Moreover, in simulated networks without churn, Bamboo achieves lookup performance comparable with Pastry, an existing DHT with a similar structure.