paper (1) - Comparing the performance of distributed hash...

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Comparing the performance of distributed hash tables under churn Jinyang Li, Jeremy Stribling, Thomer M. Gil, Robert Morris, M. Frans Kaashoek MIT Computer Science and Artificial Intelligence Laboratory { jinyang, strib, thomer, rtm, kaashoek } @csail.mit.edu Abstract A protocol for a distributed hash table (DHT) incurs communi- cation costs to keep up with churn—changes in membership—in order to maintain its ability to route lookups efficiently. This pa- per formulates a unified framework for evaluating cost and per- formance. Communication costs are combined into a single cost measure (bytes), and performance benefits are reduced to a single latency measure. This approach correctly accounts for background maintenance traffic and timeouts during lookup due to stale routing data, and also correctly leaves open the possibility of different pref- erences in the tradeoff of lookup time versus communication cost. Using the unified framework, this paper analyzes the effects of DHT parameters on the performance of four protocols under churn. 1 Introduction The design space of DHT protocols is large. While all designs are similar in that nodes forward lookups for keys through routing tables that point to other nodes, algorithms differ in the amount of state they keep: from O (1) with respect to a network size of size n [7, 9] to O (log n ) [10, 13, 14, 16] to O ( n ) [6] to O ( n ) [5]. They also differ in the techniques used to find low latency routes, in the way they find alternate paths after encountering dead intermediate nodes, in the ex- pected number of hops per lookup, and in choice of parame- ters such as the frequency with which they check other nodes for liveness. How is one to compare these protocols in a way that sep- arates incidental details from more fundamental differences? Most evaluations and comparisons of DHTs have focused on lookup hopcount latency, or routing table size in unchanging networks [2, 12, 15]. Static analysis, however, may unfairly favor protocols that keep large amounts of state, since they pay no penalty to keep the state up to date, and more state usually results in lower lookup hopcounts and latencies. This paper presents a framework for evaluating DHT al- gorithms in the face of joining and leaving nodes, in a way that makes it easy to compare tradeoffs between state main- tenance costs and lookup performance. The paper compares the Tapestry [16], Chord [14], Kelips [6], and Kademlia [10] This research was conducted as part of the IRIS project ( http://project-iris.net/ ), supported by the National Sci- ence Foundation under Cooperative Agreement No. ANI-0225660. lookup algorithms within this framework. These four reflect a wide range of design choices for DHTs. We have implemented a simple simulator that models
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This note was uploaded on 12/08/2011 for the course CS 525 taught by Professor Gupta during the Spring '08 term at University of Illinois, Urbana Champaign.

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paper (1) - Comparing the performance of distributed hash...

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