BISTRO: BitTorrent Based on Space-Time Trade-Off

doi:10.4236/cn.2013.53B2111

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Communications and Network, 2013, 5, 618-624

http://dx.doi.org/10.4236/cn.2013.53B2111 Published Online September 2013 (http://www.scirp.org/journal/cn)

BISTRO: BitTorrent Based on Space-Time Trade-Off

Roanna Lun1, Ye Zhu1, Huirong Fu2

1Departmentof Electr ical and C omputer Engi neering, C leveland State University, Clevelan d, USA

2Department of Computer Science and Engineering, Oakland University, Rochester, USA

Email: r.lun@csuohio.edu, [email protected], [email protected]

Received July 2013

ABSTRACT

Due to the content bundling and the dramatic increase of content size, the download performance in peer-to-peer net-

works has become a research focus again recently. In this paper, we propose a novel approach to improve the download

performance based on the classical space-time trade-off. With the approach, a peer can speed up local downloads in

peer-to-peer networks by contributing a portion of local hard disks for the content distribution in peer-to-peer networks.

The contribution can bring performance improve ment to each peer following the approach and in the meantime improve

the overall content distribution performance in a peer-to-pe er net work. Based o n the approach, we propose BISTRO, a

BitTorrent based on space-time trade -off. The BISTRO is compatible with the vanilla BitTorrent. Our extensive expe-

riments show that BISTRO can significantly reduce the download time.

Keywords: Peer-to-Peer Networking; BitTorrent

1. Introduction

According to the recent study [1-3], the majority of file

sharing through peer-to-peer networks is adopting the

approach called as content bundling. With the content

bundling method, publishers can combine multiple re-

lated files s uch as movies of the same genre, episodes of

one TV series, and disc images of different flavors of

Linux OS and distribute the bundled content in a single

large swarm. A user in the swarm may choose one or

more files of interest to her in the bundled content to

download [3]. In co mpariso n with d is tr ibuting o ne sin gle

file through a much smaller swarm, the c ontent b undli ng

method can greatly increase the content availability es-

pecially for unpopular content [1,2]. In the meant i me, t he

size of the content distributed through peer-to-peer net-

works is increasing significantly due to the popularity of

high-definition multimedia content. Because of the in-

crease of the content size in coupling with the content

bundling method, the content distribution performance of

peer-to-peer networks has become a research focus again.

In this paper we propose a new approach to improve

the do wnlo ad per formance of t he co ntent dis trib ution with

the content bundling method through peer-to-peer net-

works. The main idea of the approach originates from the

classical space-time trad e-off [4]. In algorithm researches,

the tradeoff can be used to reduce the time to solve a

problem at the cost of the space efficiency, i.e., more

memory or more storage consumption.

As the storage becomes cheaper, thanks to Moore’s

Law, the peers in peer-to -peer networks have more disk

space that can be used to trade off the time of download-

ing co ntent . In the new approach, a peer in a swarm con-

tributes a portion of local hard disk for the content dis-

trib utio n eve n whe n the pee r is no t downloading any file.

The peer can benefit from the blocks in the contributed

storage since these file blocks can be used to exchange

back file blocks needed by the peer when the peer is in

the downloading phase.

Our major contributions are summarized as follows:

 We propose a novel approach to improve the perfor-

mance of content distribution through peer-to-peer net-

works. The approach is based on the classical space-

time trade-off.

 We are particularly interested in improving the per-

formance of the Bit Torrent protocol due to its do-

mina nce in peer-to-peer networks. We develop Bit-

Torrent based on space-time trade-off (BISTRO) with

the new approach.

 We verify the new approach with extensive experi-

ment s on BISTRO. Our experiments show that the

new approach can significantly speed up content dis-

tribution, i.e., and reduce the do wnload time.

The rest of the paper is organized as follows: Section 2

defines the problem and briefly introduces the BitTorrent

protocols. The detail of the new approach is described in

Section 3. We evaluate the performance of BISTRO with

extensive experiments in Section 4. Section 5 reviews

R. LUN ET AL.

619

related works. We discuss the approach and outline the

future work in Section 6. We conclude the paper in Sec-

tion 7.

2. Problem Definition

The goal of this paper is to improve the download per-

formance for peers joining content distribution with the

content bundling method. We are particularly interested

in BitTo rrent due to its do minance in content distr ibution

through peer-to-peer networks: 1) More than 79% of In-

ternet peer-to-peer bandwidth is used by BitTorrent [5]. 2)

The estimated number of monthly BitTorrent users is

more t han a quar ter bill ion, whi ch is more than the num-

ber of active users of YouTube and Facebook combined

[6].

First we would li ke to revie w fundamentals of BitT or-

rent related to our approach. BitTorrent allows Internet

users (peers) who are intereste d in do wnloading the sa me

content to form a network (swarm). In a swarm, peers

can download and upload from each other simultaneous-

ly. To share a file or bundled files, a torrent file t hat con-

tains metadata about the shared files must be created.

The content distribution is coordinated by a tracker spe-

cified in the torrent file. To join the swarm, a peer first

obtains the tracker’s URL in the torrent file, and then

connects to the tracker to ask for other peers’ information.

Periodically, peers connect to the tracker to provide their

downloading status. The tracker also lets peers share in-

formation.

In BitTorrent, a large file is divided into smaller file

blocks of a f ixed size for distribution. T he typical siz e of

a file block is 256 KB. Once a peer completely receives a

new block of the file, it becomes a possible provider of

that block for other peers immediately. Each peer main-

tains the status of each file block which indicates whether

the file block is available for uploading or not. After a

file block is completely downloaded, the status of that

block will be marked as available for uploading to other

peers. The file block statu s is communicated a mon g peers

thro ugh BITF IELD messa ge [7].

One of the most important policies in the BitTorrent

protocol is the tit-for-tat incentive policy, which is de-

signed to prevent free riding. By the tit-for-tat policy, a

peer with a low ratio of the upload rate versus the do wn-

load rate is choked by data providers. Once the upload

activities increased, meaning that the ratio is going up,

the peer gets unchoked. Then the peer can continue to

download desired file blocks. In other words, more upl-

oad contribution made by a peer can bring the peer more

file blocks to download.

We believe a new approach to improve the download

performance s hould sati sfy the follo wing require ments: 1)

The new app roach shoul d be c ompatib le wi th curr ent Bit-

Torrent protocols because of the huge user base. In other

words, peers adopting the new approach should be able

to exchange file blocks with vanilla BitTorrent peers

according to the tit-for-tat policy and help content distri-

bution in a swarm consisting of both vanilla BitTorrent

peers and the peers adopting the new approach; 2) The

new approach should bring in extra incentives to moti-

vate peers to adopt the new approach. Otherwise no peers

will be interested in adopting the new approach.

3. BISTRO: BitTorrent Based on

Space-Time Trade-Off

In this section, we describe the approach based on the

space-time trade-off and present BISTRO. We begin the

section with an overview of the approach and then pro-

ceed with the details of BISTRO. The rationale behind

the new approach and the incentives for peers to use the

new approach are introduced at the end of the section.

3.1. Overview

The novel approach to improve the download perfor-

mance in peer-to-peer networks is based on the classical

space-time trade-off, which is often used to speed up

program execution at the cost of increased memory usage

or storage usage in algorithm researches. We extend the

idea to the peer-to-peer networks. To speed up local

downloading, a peer can contribute a portion of the local

hard disk to the content distribution. The storage contri-

buted by the peer can increase the local download speed

since more file blocks, including file blocks in the con-

tributed storage can be used for exchanging desired file

blocks.

A BISTRO peer can be in one of the two phases: the

dormant phase and the download phase. In the dormant

phase, a peer is not downloading any desired files. In-

stead the peer is simply participating in the content dis-

tribution and filling the local storage contributed to the

conte nt di str ibuti o n. In t he d or mant p hase, wh en the co n-

tribu ted stora ge is fu ll, some re place ment me thods ar e used

to optimize the storage. When the peer becomes inter-

ested in downloading some files in the bundled content,

such as the next TV episode in a bundle of TV series, it

changes into the download phase. During the download

phase, the file blocks in the contributed storage can be

used to exchange desired file blocks with other peers.

The details of the BISTRO are described below.

3.2. Design of BISTRO

In this section, we first describe the preliminaries includ-

ing storage configurations and then describe the details

of the dormant phase and the download phase. To avoid

unnecessary repeating of t he original BitTorrent protoco l,

we focus on the difference between BISTRO and the

R. LUN ET AL.

620

vanilla BitTorrent.

1) Preliminaries: In this paper, we assume the content

files are bundled. A peer joining the distribution of the

bundled content may select one or more files in the con-

tent bundle to download [3].

Each peer has a portion of local disk space allocated

for use by BISTRO to speed up local downloads. In this

paper, we call the portion of the local disk space as the

contributed storage. The storage is divided into two parts:

the content part and the management part. The content

part is used to store file blocks and it takes the majority

of t he space al located as the contributed stora ge. The con-

tent part is divided into blocks and the size of each block

in the content part is the same as the size of file blocks

exchanged among BitTorrent peers so that each block of

the content part can be used to store one file block. Since

most BitTo rrent swarms use 256 KB as the block size so

the size of the block in the contributed storage is set to

256 KB by default1. The management part is used to

store information required to manage the storage. For

example, the information needed by the block replace-

ment method is kept in the management pa rt.

2) Dormant Phase: In the dormant phase, a peer has

no desire to download a file from a swarm yet. The peer

joins the swarm simply to participate in the content dis-

tribution to fill and optimize its contributed storage. So

that later, the file blocks in the storage can be used by the

peer to maximize the return, i.e., exchange back its de-

sired file blocks according to the tit-for-tat policy used

by BitTorrent. The pre-filled storage is equivalent to the

pre-calculated results stored in memory. In the classical

time-space trade-off, the pre-calculated results are used

to speed program execution. In BISTRO, the prefilled

storage is used to speed up both local downloads and the

content distribution to other peers.

For the dormant phase we extend the vanilla BitTor-

rent as follows:

BITFIELD Message: A vanilla BitTorrent peer ex-

changes the BITFIELD messages with other peers to an-

nounce the file blocks that have already downloaded. A

BISTRO peer will also announce the file blocks in its

contributed storage so that other peers can download

these file blocks in the contributed storage.

Storage Management: When the storage is not full, a

BISTRO peer simply stores downloaded file blocks in

the contributed storage since these file blocks are not of

interest by the peer in the dormant phase. But when the

storage is full and new file blocks are downloaded, cer-

tain blocks in the contributed storage may have to be

replaced. Obviously the block replacement method is im-

portant to the performance: 1) Because of the tit-for-tat

policy, file blocks in the contributed storage are essen-

tially bargain chips used to exchange back desired file

blocks when the peer is in the download phase. So it is

important for a peer to keep most useful barga in chips i n

the contributed storage to speed up the file downloading

in the do wnload p hase; 2) In the dormant phase, the peer

has no interest in the blocks within the contributed sto-

rage. But the file blocks held by the dormant peers affect

the content distribution to other peers in the swarm. In

this paper, we propose two storage replacement methods:

 Random Replacement: The peer randomly selects a

file block in the contributed storage and replaces the

file block with a newly downloaded file block.

 Least Frequently Requested (LFR): In the LFR me-

thod, the least frequently requested, i.e., the most un-

popular file blocks are replaced. To keep track of re-

quests on each file block in the contributed storage, a

request count associated with each file block is kept

in the management part of the storage. The heuristic

behind the met hod is that the most popular file blo cks

are the most useful bargain chips to exchange back

desired file blocks in the download phase.

For different content distribution networks, the actual

implementation of the dormant phase may vary in terms

of participating in the content distribution without the

desire to download a file. In some content distribution

networks, it is possible for a peer to participate in the

distribution passively as a cache node [8]. In other type

of content distribution networks, a peer in the dormant

phase has to send download requests to participate in the

content distribution. For the second type of content dis-

tribution networks, the peer in the dormant phase re-

quests file blocks randomly or simple select a file ran-

domly from the bundled content to download. In BISTRO,

the second implementation method is used.

The length o f the do rmant p hase depend s on whe n the

peer beco mes interested in downloading files. So me peers

may want to simply contributing the storage for content

distribution so that they can use the file blocks in the

storage to speed up their future download. Some peers

may want to download desired files immediately after

joining a BitTorrent swarm.

3) Download Phase: Whenever a BISTRO peer be-

comes interested in downloading files in the swarm, the

peer is changed into the download p hase.

A BISTRO peer in the download phase acts largely the

same as a regular peer in the vanilla BitTorrent. The ma-

jo r differe nce is t hat from the begi nning o f the downlo ad

phase, the peer has bargain chips, i.e., file blocks in the

contributed storage. So when a BISTRO peer advertises

the file blocks availab le for sharing, the BI TFIELD mes-

sage also contains the availability of the file bloc ks i n the

contributed storage. So that other peers can request and

download the file blocks in the contributed storage.

In the download phase, the contributed storage is not

1The

block size in the contributed storage can be changed according to

the change of the block size used by BitTorrent swarms.

R. LUN ET AL.

621

updated. In other words, a peer in the download phase

only requests and downloads file blocks in its desired

files. In this way, the download bandwidth is only used

for downloading the desired files. Since the contributed

storage is filled and optimized only in the dormant phase,

the benefits brought by the contributed storage are at no

cost to the actual download ing of the desired files.

3.3. Design Rationales

In the rest of this section, we introduce our design con-

siderations and analyze the benefits of BISTRO.

One of the major design considerations is to make

BISTRO compatible with the current BitTorrent proto-

cols because: 1) BitTorrent is the dominant protoc ol used

in the content distribution with a huge user base [9]; 2)

Some devices running BitTorrent may not have large

amount of disk space available for BISTRO. For example,

home routers with the open source firmware such as DD-

WRT [10] can r un B itTo rrent for co ntent dist rib ution. But

the storage space in the home routers is relatively small.

BIST RO is compatible with B itT orrent proto cols since

a vanilla BitTo rrent peer is equivalent to a BIST RO peer

with an empty contributed storage. The messages ex-

changed among BISTRO peers are in the same format as

the messages exchanged among the vanilla BitTorrent

peers.

The second major design consideration is on the in-

centive to encourage peers to contribute a part of the disk

space for the content distribution. Obviously without in-

centives, mo st of the p eers will not make the contribution.

The incentive for a peer to use BISTRO is t he less down-

load time for future downloads. According to the tit-for-

tat policy, the incentive policy in BitTorrent to prevent

free-ridi ng, a hig her up loa d ra te can e xc han ge fo r a higher

download rate. If the contributed storage is filled with

useful bargain chips, the peer holding the storage will

benefit from a much faster download speed. So essen-

tially BISTRO amplifies the benefits brought by follow-

ing the tit-for-ta t policy. In other words, BISTRO is more

encouraging in motivating peers to contribute the local

storage in content distribution.

Because of the contributed storage, BISTRO can greatly

increase the content availability and in turn speed up the

content distrib ution in BitT orrent swarms. T he benefit on

the content availability is obvious since the contributed

storage can greatly increase the number of file blocks in

swarms. We analyze the benefit on the content distribu-

tion with the model established for content bundling.

According to the content bundling model in [2], the mean

download time of a file, denoted as [T], can be derived

as:

[ ]

ET P

= +⋅

(1)

Where s donates the file size, μ donates the mean

download rate of peers, r donates the arrive rate of file

content publishers, i.e., seeds in BitTorrent, and P do-

nates the unavailability of file content. As shown in the

equation, E [T] decreases with P. In other words, the

download time decreases when the file content unavaila-

bility decreases. Hence as more file blocks are available

at any given time in a BitTorrent swarm because of the

contributed storage, the download time decreases. So the

download performance is improved. The analysis theo-

retically proves that BISTRO can speed up the content

distribution.

We evaluate the performance of BISTRO with exten-

sive experiments described below.

4. Performance Evaluation

In this section we first introduce the experiment setup

and then present results of extensive experiments on BI-

STRO. Due to the space limit, we leave the experiments

on size of the contributed storage and length of the dor-

mant phase in the companion technical report [11].

4.1. Experimental Settings

We evaluate BISTRO with the ns2 simulator [12]. Since

BIST RO is b ased on BitT orrent and it is co mpatible with

BitTorrent, we implement BISTRO by adding the follow-

ing key components to the vanilla BitTorrent patch de-

veloped by Kolja Eger [7]: 1) A storage class is added

and it includes the storage block structure and the func-

tions t o manage t he stora ge. The b asic infor mation a bout

a storage block, such as the block index, the file ID, the

request count, and its status, is defined in this class. In

addition, this class defines the implementation of block

replacement methods; 2) We add functions necessary to

allow a peer in the dormant phase to randomly request

file blocks for building up the contributed storage and to

exchange blocks in the contributed storage with other

peers; 3) An initializatio n fun ction is added to set the file

block status based on pre-filled storage bloc k in formation.

If a fi le bl ock is found in the contributed storage, then the

status of that file bloc k is set to be a vailable, otherwise it

is set to unavailable; 4) Functions are added or modified

to allow a peer in the download phase to share the file

blocks in the contributed storage in exchange for desired

file blocks.

In the following experiments, we assume the down-

load capacity and the upload capacity of each peer are 16

Mbps and 2 Mbps respectively.

4.2. Performance Metrics

We evaluate the download performance with the down-

load time defined as the time to complete downloading a

R. LUN ET AL.

622

file or files. The performance metric used to benchmark

one network is the average download time of all peers

participa ting in the BitTorrent network. Since we do not

study effectiveness of any incentive methods in BitTor-

rent in this paper, we assume peers are not required to

stay in networ k af te r c ompleting downloading all data.

As described in Section 3, a BISTRO peer has no de-

sire to download any file and the peer is simply contri-

buting a por tion of local disk to participate in the content

distr ib ut io n p ass i vel y. So the l ength of t he d o rma nt p has e

is not a part of download time. In the download phase, a

BISTRO peer is actively downloading a desired file so

the download time is the length of the download phase

for a BISTRO peer.

4.3. Size of the Contributed Storage

In this set of experiments, we investigate the download

performance with different content file sizes. Among the

100 peers included in this set of experiments, half o f the

peers are BISTRO peers with 50 MB or 500 MB contri-

buted storage and the other half are vanilla BitTorrent

peers. We vary the file size from 100 MB to 1 GB. Fig-

ure 1 shows the experiment results with 50 MB and 500

MB contributed storage. From Figure 1, we can observe:

1) The average download time of BISTRO peers in a

swarm consisting of half BISTRO peers and half vanilla

peers is cons istently 30% less than the do wnload time of

peers in the BitTorrent swarm consisting of only vanilla

BitTorrent peers. It means BISTRO can greatly reduce

the download time; 2) Even the download time taken by

the vanilla peers in the swarm with half BISTRO peers

and ha l f va nil la pe er s i s 2 0% les s tha n the d ownloa d t ime

taken by the peers in the BitTorrent swarm consisting of

only vanilla BitTorrent peers. This observation means

BISTRO can also help content distribution to vanilla

peers; 3) The difference between the download time of

BISTRO peers using any of the two block replacement

methods and t he download ti me of the vanilla BitTor rent

peers is increasing with the file size. In other words, the

performance improvement over the vanilla BitTorrent

increases with the file size; 4) The performance of BI-

STRO peers with the LFR replacement method is close

to the performance of BISTRO peers with the random

replacement method for small file size. When the down-

load file is larger than 700 MB, the LRF replacement

methods outperform the random replacement methods.

4.4. Number of Peers

In this set of experiments, we study the performance of

BISTRO with different swarm sizes, i.e., different num-

ber of peers. Figure 2 shows the results on the random

replacement method and the LFR replacement method.

(a) (b)

Figure 1. D ownload Time vs. Download File S ize.

(a) (b)

Figure 2 . D ownload Time vs. Number of Peers .

R. LUN ET AL.

623

From these two figures, we again observe the large per-

formance improvement of BISTRO over the vanilla Bit-

Torrent. Figure 2 also shows that the performance im-

provement increases with the number of peers.

In summary, the experiment results described above

indicate that BISTRO can significantly improve the down-

load performance. T he performance improvement brought

by BISTRO is consistently more than 30%. Our experi-

ments also show that a relatively small contributed sto-

rage can bring signi fi cant performance impro vement.

5. Related Work

Since its debut in 2001, BitTorrent, the most popular

peer-to-peer file sharing protocol, has attracted a signifi-

cant amount of researches on its performance. In [13] the

improvement of download performance is achieved by

collaborative download mechanism. The mechanisms

presented in [14,15] have shown that cooperation be-

tween peers can also reduce peer’s download time. The

approaches of utilizing localization among peers for re-

ducing overlay traffic and improving performance were

proposed in [16,17]. BISTRO improves the download

performance with the contributed storage to trade the

local storage for faster download speed.

Lee et al. [8] proposed to increase content availability

in multi-swarm BitTorrent networks by caching. The pro-

posed approach requires significant changes to the Bit-

Torrent protocols to support the exchange of file blocks

in multiple swarms and it involves a large amount of

messages exchanged between multiple trackers.

Caching at the ISP level of peer-to-peer networks is

proposed by Lehrieder et al. [18] to improve the perfor-

mance of content distribution. The ISP-level approach

decreases the inter-ISP traffic by storing popular contents

at the ISP level so that the remote peers do not have to

download them from peers within the ISP. BISTRO im-

proves the download performance at the peer level and it

is compatible with the vanilla BitTor rent protocols.

To the best of our knowledge, BISTRO is the first at-

tempt to speed up downloads in peer-to-peer ne twor ks by

contributing the local storage space based on the space-

time trade-off.

6. Discussion and Future Work

The experiments show that BISTRO can greatly reduce

the download time when in comparison with the vanilla

BitTorrent. But the LRF replacement method used in

BISTRO is not significantly better than the random re-

placement method. Similar results have been reported on

cache design in computer architecture [19]: The Least-

Recently Used (LRU) method used for cache block re-

placement is only about 1% better than random replace-

ment method.

Alt houg h the pe rfor ma nce res ults fro m our e xperi ments

are consistent with the benchmark results reported in [19]

in terms of the difference between the LRF/LRU re-

placement methods and the random replacement methods,

we believe it is possible to further improve BISTRO’s

performance by improving the replacement method. We

plan to make more information such as request trend

available to replacement methods. We will compare dif-

ferent replacement methods in terms of performance gain

and processing overhead on the additional information.

We also plan to establish a theo retica l model to pr edict

the performance of the approach based on the space-time

trade-off. The model can be used by peer-to-peer net-

work users to determine the tradeoff between the down-

load performance and the amount of local storage con-

tributed for content distribution.

7. Conclusion

In this paper we present a novel approach to improve

peers’ do wnload per formance based on the class ical space-

time trade-off. The experiment results have shown that

the performance improvement over the vanilla BitTorrent

is average 30% consistently with different tests. Given

the popularity of the low-cost and high-capacity hard

disks, we believe the new approach is very promising in

practice.

8. Acknowledgements

This work was supported in part by the US National

Science Foundation (NSF) under grant No. 1144644. Any

opinions, findings, conclusions, and recommendations in

this paper are those of the authors and do not necessarily

reflect the views of the funding agencies.

REFERENCES

[1] D. Menasche, G. Neglia, D. Towsley and S. Zilberstein,

“Strategicreasoning about Bundling in Swarming Sys-

tems,” International Conference on Game Theory for

Networks, 2009, pp. 611-620.

[2] D. S. Menasche, A. A. de Aragao Rocha, B. Li, D. F.

Towsley and A. Venkataramani, “Content Availability

and Bundling in Swar ming S ystems,” Proceedings of the

ACM Conf er ence on Emerging Net w orking Experiments

and Technology, 2009, pp. 121-132.

[3] J. Han, S. Kim, T. Chung, T. T. Kwon, H.-C. Kim and Y.

Choi, “Bundling Practice in Bittorrent: What, How, and

Wh y,” Proceedings of the 12th ACM SIGMETRICS/

PERFORMANCE Joint International Conference on

Measurement and Modeling of Computer Systems, 2012,

pp. 77-88.

[4] A. Levitin, “Introduction to the Design and Analys is of

Algorithms, 3/E,” Addison-Wesley, 2012.

[5] In ternetob s er vat ory.net, “Internet Status Report”.

R. LUN ET AL.

624

http://www.internetobservatory.net

[6] A. Carr, “Bittorrent Has More Users Netflix and Hulu

Combined-and Doubled”.

http://www.fastcompany.com/1714001

[7] K. Eger, “Bittorrent in ns-2, Patch for NS-2.29”.

https://sites.google.com/site/koljaeger/bittorrent-simulatio

n-in-ns-2

[8] H. Lee, A. Nakao and J. Kim, “Multi-Swarm Collabora-

tion for Improved Content Availability in Bittorrent-Like

S ys t e m s ,” Proceedings of Consumer Communications and

Networking Conference (CCNC), IEEE, 2011, pp. 565-

569.

[9] A. M. Mateus and J. M. Peha, “Quantifying Global

Transfers of Copyrighted Content Using Bittorrent”.

http://papers.ssrn.com/abstract=1985737

[10] DD-WRT.co m, “Unleash Your Router”.

http://www.dd-wrt.com

[11] R. Lun, Y. Zhu and H. Fu, “Bistro: Bittorrent Based on

Space-Time Trade off,” Department of Electrical and

Comput er Engineerin g, Cleveland State Un iversity, Tech.

Rep. 20130423a, 2013.

http://academic.csuohio.edu/zhu_y/techreport/20130423a.

pdf

[12] ISI.ed u, “The Network Simulator NS 2”.

http://www.isi.edu/nsnam/ns

[13] N. Zeilemaker, M. Capota, A. Bakker and J. Pouwelse,

“Tribler: Searchand Stream,” IEEE International Confe-

rence on Peer-to-Peer Computing (P2P), 2011, pp. 164-

165.

[14] C.-J. Wu, C.-Y. Li and J.-M. Ho, “Improving the Down-

load Time of BitTorrent-Like Systems,” IEEE Interna-

tional Conference on Communications, 2007, pp. 1125-

1129.

[15] M. Lingjun, P.-S. Tsang and K.-S. Lui, “Improving File

Distribution Performance by Grouping in Peer-to-Peer

Networks,” IEEE Transactions on Network and Service

Management, 2009, pp. 149 -162.

[16] R. Rahman, M. Meulpolder, D. Hales, J. Pouwelse, D.

Epema and H. Sips, “Improving Efficiency and Fairness

in p2p Systems with Effort-Based Incentives,” IEEE In-

ternational Conference on Communications (ICC), 2010,

pp. 1-5.

[17] C. Tian, X. Liu, H. Jiang, W. Liu and Y. Wang, “IM-

PROVING BitTorrent Traffic Performance by Exploiting

Geographic Locality,” Global Telecommunications Con-

ference, 2008, pp. 1-5.

[18] F. Lehrieder, G. Dan, T. Hossfeld, S. Oechsner and V.

Singeorzan, “Cachi ng for Bittorrent-Like p2p Systems: A

Simple Fluid Model and Its Implications,” IEEE/ACM

Transactions on Networking, 2011.

[19] J. L. Hennessy and D. A. Patterson, “Computer Architec-

ture: A Quantitative Approach,” 3rd Editon, Morgan

Kaufmann Publ ishe r s Inc., San Francisco, 2002.