207 research outputs found
BitTorrent Experiments on Testbeds: A Study of the Impact of Network Latencies
In this paper, we study the impact of network latency on the time required to
download a file distributed using BitTorrent. This study is essential to
understand if testbeds can be used for experimental evaluation of BitTorrent.
We observe that the network latency has a marginal impact on the time required
to download a file; hence, BitTorrent experiments can performed on testbeds
Studying Social Networks at Scale: Macroscopic Anatomy of the Twitter Social Graph
Twitter is one of the largest social networks using exclusively directed
links among accounts. This makes the Twitter social graph much closer to the
social graph supporting real life communications than, for instance, Facebook.
Therefore, understanding the structure of the Twitter social graph is
interesting not only for computer scientists, but also for researchers in other
fields, such as sociologists. However, little is known about how the
information propagation in Twitter is constrained by its inner structure. In
this paper, we present an in-depth study of the macroscopic structure of the
Twitter social graph unveiling the highways on which tweets propagate, the
specific user activity associated with each component of this macroscopic
structure, and the evolution of this macroscopic structure with time for the
past 6 years. For this study, we crawled Twitter to retrieve all accounts and
all social relationships (follow links) among accounts; the crawl completed in
July 2012 with 505 million accounts interconnected by 23 billion links. Then,
we present a methodology to unveil the macroscopic structure of the Twitter
social graph. This macroscopic structure consists of 8 components defined by
their connectivity characteristics. Each component group users with a specific
usage of Twitter. For instance, we identified components gathering together
spammers, or celebrities. Finally, we present a method to approximate the
macroscopic structure of the Twitter social graph in the past, validate this
method using old datasets, and discuss the evolution of the macroscopic
structure of the Twitter social graph during the past 6 years.Comment: ACM Sigmetrics 2014 (2014
Network Non-neutrality Debate: An Economic Analysis
This paper studies the economic utilities and the quality of service (QoS) in
a two-sided non-neutral market where Internet service providers (ISPs) charge
content providers (CPs) for the content delivery. We propose new models on a
two-sided market which involves a CP, an ISP, end users and advertisers. The CP
may have either the subscription revenue model (charging end users) or the
advertisement revenue model (charging advertisers). We formulate the
interactions between the ISP and the CP as a noncooperative game problem for
the former and an optimization problem for the latter. Our analysis shows that
the revenue model of the CP plays a significant role in a non-neutral Internet.
With the subscription model, both the ISP and the CP receive better (or worse)
utilities as well as QoS in the presence of side payment at the same time.
However, with the advertisement model, the side payment impedes the CP from
investing on its contents.Comment: 15 pages, 10 figure
Understanding the Properties of the BitTorrent Overlay
In this paper, we conduct extensive simulations to understand the properties
of the overlay generated by BitTorrent. We start by analyzing how the overlay
properties impact the efficiency of BitTorrent. We focus on the average peer
set size (i.e., average number of neighbors), the time for a peer to reach its
maximum peer set size, and the diameter of the overlay. In particular, we show
that the later a peer arrives in a torrent, the longer it takes to reach its
maximum peer set size. Then, we evaluate the impact of the maximum peer set
size, the maximum number of outgoing connections per peer, and the number of
NATed peers on the overlay properties. We show that BitTorrent generates a
robust overlay, but that this overlay is not a random graph. In particular, the
connectivity of a peer to its neighbors depends on its arriving order in the
torrent. We also show that a large number of NATed peers significantly
compromise the robustness of the overlay to attacks. Finally, we evaluate the
impact of peer exchange on the overlay properties, and we show that it
generates a chain-like overlay with a large diameter, which will adversely
impact the efficiency of large torrents
How to Network in Online Social Networks
In this paper, we consider how to maximize users' influence in Online Social
Networks (OSNs) by exploiting social relationships only. Our first contribution
is to extend to OSNs the model of Kempe et al. [1] on the propagation of
information in a social network and to show that a greedy algorithm is a good
approximation of the optimal algorithm that is NP-hard. However, the greedy
algorithm requires global knowledge, which is hardly practical. Our second
contribution is to show on simulations on the full Twitter social graph that
simple and practical strategies perform close to the greedy algorithm.Comment: NetSciCom 2014 - The Sixth IEEE International Workshop on Network
Science for Communication Networks (2014
Small Is Not Always Beautiful
Peer-to-peer content distribution systems have been enjoying great
popularity, and are now gaining momentum as a means of disseminating video
streams over the Internet. In many of these protocols, including the popular
BitTorrent, content is split into mostly fixed-size pieces, allowing a client
to download data from many peers simultaneously. This makes piece size
potentially critical for performance. However, previous research efforts have
largely overlooked this parameter, opting to focus on others instead. This
paper presents the results of real experiments with varying piece sizes on a
controlled BitTorrent testbed. We demonstrate that this parameter is indeed
critical, as it determines the degree of parallelism in the system, and we
investigate optimal piece sizes for distributing small and large content. We
also pinpoint a related design trade-off, and explain how BitTorrent's choice
of dividing pieces into subpieces attempts to address it
Swarming Overlay Construction Strategies
Swarming peer-to-peer systems play an increasingly instrumental role in
Internet content distribution. It is therefore important to better understand
how these systems behave in practice. Recent research efforts have looked at
various protocol parameters and have measured how they affect system
performance and robustness. However, the importance of the strategy based on
which peers establish connections has been largely overlooked. This work
utilizes extensive simulations to examine the default overlay construction
strategy in BitTorrent systems. Based on the results, we identify a critical
parameter, the maximum allowable number of outgoing connections at each peer,
and evaluate its impact on the robustness of the generated overlay. We find
that there is no single optimal value for this parameter using the default
strategy. We then propose an alternative strategy that allows certain new peer
connection requests to replace existing connections. Further experiments with
the new strategy demonstrate that it outperforms the default one for all
considered metrics by creating an overlay more robust to churn. Additionally,
our proposed strategy exhibits optimal behavior for a well-defined value of the
maximum number of outgoing connections, thereby removing the need to set this
parameter in an ad-hoc manner
Pushing BitTorrent Locality to the Limit
Peer-to-peer (P2P) locality has recently raised a lot of interest in the
community. Indeed, whereas P2P content distribution enables financial savings
for the content providers, it dramatically increases the traffic on inter-ISP
links. To solve this issue, the idea to keep a fraction of the P2P traffic
local to each ISP was introduced a few years ago. Since then, P2P solutions
exploiting locality have been introduced. However, several fundamental issues
on locality still need to be explored. In particular, how far can we push
locality, and what is, at the scale of the Internet, the reduction of traffic
that can be achieved with locality? In this paper, we perform extensive
experiments on a controlled environment with up to 10 000 BitTorrent clients to
evaluate the impact of high locality on inter-ISP links traffic and peers
download completion time. We introduce two simple mechanisms that make high
locality possible in challenging scenarios and we show that we save up to
several orders of magnitude inter-ISP traffic compared to traditional locality
without adversely impacting peers download completion time. In addition, we
crawled 214 443 torrents representing 6 113 224 unique peers spread among 9 605
ASes. We show that whereas the torrents we crawled generated 11.6 petabytes of
inter-ISP traffic, our locality policy implemented for all torrents would have
reduced the global inter-ISP traffic by 40%
I Know Where You are and What You are Sharing: Exploiting P2P Communications to Invade Users' Privacy
In this paper, we show how to exploit real-time communication applications to
determine the IP address of a targeted user. We focus our study on Skype,
although other real-time communication applications may have similar privacy
issues. We first design a scheme that calls an identified targeted user
inconspicuously to find his IP address, which can be done even if he is behind
a NAT. By calling the user periodically, we can then observe the mobility of
the user. We show how to scale the scheme to observe the mobility patterns of
tens of thousands of users. We also consider the linkability threat, in which
the identified user is linked to his Internet usage. We illustrate this threat
by combining Skype and BitTorrent to show that it is possible to determine the
file-sharing usage of identified users. We devise a scheme based on the
identification field of the IP datagrams to verify with high accuracy whether
the identified user is participating in specific torrents. We conclude that any
Internet user can leverage Skype, and potentially other real-time communication
systems, to observe the mobility and file-sharing usage of tens of millions of
identified users.Comment: This is the authors' version of the ACM/USENIX Internet Measurement
Conference (IMC) 2011 pape
Spying the World from your Laptop -- Identifying and Profiling Content Providers and Big Downloaders in BitTorrent
This paper presents a set of exploits an adversary can use to continuously
spy on most BitTorrent users of the Internet from a single machine and for a
long period of time. Using these exploits for a period of 103 days, we
collected 148 million IPs downloading 2 billion copies of contents. We identify
the IP address of the content providers for 70% of the BitTorrent contents we
spied on. We show that a few content providers inject most contents into
BitTorrent and that those content providers are located in foreign data
centers. We also show that an adversary can compromise the privacy of any peer
in BitTorrent and identify the big downloaders that we define as the peers who
subscribe to a large number of contents. This infringement on users' privacy
poses a significant impediment to the legal adoption of BitTorrent
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