Evaluation of correlation between successful lookup ratio with network size and churn rate of chord in wireless

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EVALUATION OF CORRELATION BETWEEN SUCCESSFUL LOOKUP RATIO

WITH NETWORK SIZE AND CHURN RATE OF CHORD IN WIRELESS

COMMUNICATION ENVIRONMENT

Vu Thanh Vinh1*

, Nguyen Chan Hung2

, Nguyen Tuan Anh3

1

The Faculty of Information Technology – TNU

2HaNoi University of Technology,

3

ThaiNguyen University

ABSTRACT

One of the most critical problems of peer to peer (P2P) multimedia applications is the effect of

churn to the efficiency of locating data items, which is a fundamental function of P2P networks.

Especially, when P2P network extends to the mobile environment, churn effect may heavily affect

the whole network and disrupt normal service. In this paper, we adapt a mechanism named atomic

ring maintenance for Chord to mitigate the effect of churn. Simulation results show significant

improvement in successful ratio of lookups for modified Chord protocol in high churn condition

while latency of successful lookups is as good as that in basic Chord. Simultaneously, we also

evaluate correlation between successful lookup ratio and network size and churn rate.

Keywords: P2P, Peer to Peer, distributed hash tables, DHTs, Chord, DHT performance, latency,

lookup, evaluation Chord

INTRODUCTION1

Peer to peer applications, such as P2PVoD,

P2P streaming, P2P file sharing have been

paid much attention from both industry and

academia for the last few years thanks to the

bandwidth efficiency of P2P network and the

fast growth of broadband Internet. Nowadays,

these applications not only operate on

desktop/laptop computers but also on mobile

and handheld devices. However, mobile

nodes tend to join and leave network very

frequently due to the intermittent of

communication link and user behavior. As a

result, the efficiency of locating a specific

data on the P2P network (i.e. a piece of video

chunk or a file) dramatically decreases under

this condition [2]. While this phenomenon is

not well aware in file sharing applications, it

can severely impact P2PVoD and

P2PStreaming applications, where timing has

strong effect on video and audio quality.

However, since structured P2P networks were

originally designed for wired network, where

nodes join and leave network at much slower

rate, they need significant modifications to

work in mobile environment.

In this study, we adapted atomic ring

maintenance mechanism for Chord protocol, a

typical ring-based DHT, to reduce lookup

Tel: 0982782966; Email: [email protected]

inconsistency under the effect of churn. We

also successfully implemented a modified

Chord protocol in Oversim simulator and

evaluate its performance under high churn rate

together with original Chord protocol.

This paper is structured as follows: In

section 2, we give a brief overview of

related studies. Section 3 review Chord

problems under churn, and illustrate the

modified Chord protocol. Section 4 is given

describing simulation setup and analyzing

the results. Finally, section 5 concludes this

paper with an outlook to future work.

RELATED STUDIES

Our work was inspired by the work of Ali

Ghodsi [1] namely “Atomic ring

maintenance”, which again derived from [6].

Differ from their approach, we only modified

the join process and consider leave as a

failure since this is the common case in

mobile wireless environment. In addition, we

adapt a hybrid stabilization mechanism

whereproactive stabilization is activated when

join activities happen and periodical

stabilization still run in background.

Moreover, Ali Ghodsi only proposed several

algorithms and proved it using analytical

method without fully evaluates their

performance. S. Rhea et al [4] using

emulation of 1000 DHT nodes to evaluate

several DHT mechanisms under churn. They