Improving lookup reliability in Kad

Authors: Bingshuang Liu Tao Wei Chao Zhang Jun Li Jianyu Zhang

Publish Date: 2013/10/20

Volume: 8, Issue: 1, Pages: 156-170

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Abstract

Kad is one of the most popular peertopeer P2P networks deployed on today’s Internet It provides support for filesharing applications such as eMule and aMule and serves millions of users Its reliability impacts not only the availability of filesharing services but also the capability of supporting other Internet services However in today’s Kad network its lookup operation’s success ratio is lower than 91 and not suitable for critical applications In this paper we investigate why Kad lookup fails and propose several new solutions We build a measurement system called Anthill to analyze Kad’s communication process quantitatively and figure out that the causes of Kad’s lookup failures can be classified into four categories packet loss selective Denial of Service nodes search sequence miss and publish/search space miss The first two are due to the environment changes the third is caused by the detachment of routing operations and content operations in Kad and the last one shows the limitations of the Kademlia DHT algorithm under Kad’s current configuration Based on the analysis we propose corresponding approaches for Kad including packetretransmission neighborhood lookup and βadjusting We have systematically measured the effectiveness and efficiency of these approaches and then give several recommendations for adoption in different situations The improved version of Kad can achieve a success ratio of 998 for lookup operations with only a moderate communication overhead while its average lookup latency is reduced significantly to only about 1 second Our work shows that with proper configurations and improvements Kad can work much better and is capable of supporting more Internet services

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