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BT system modeling has great importance for understanding the system performance and improving the protocol design. The challenge of accurate BT system modeling lies in the complicated peer behavior in the dynamic and heterogeneous system. In this paper, we propose a bottom-up model to simplify the performance analysis and increase the modeling accuracy, in which local transitions of the system lead to global macroscopic descriptions by integration. To be specific, we evaluate the download rate of each individual peer by estimating the probability of a connection being made, and the probability of a peer being unchoked, and then later integrate the analysis of each individual peer into the description of the whole system. Such a model characterizes both core parts of the protocol and main features of the system and requires far fewer restrictive assumptions than that used before. By using the model, we provide some interesting insights into setting of parameters, power of free-riding, effect of bandwidth distribution and effectiveness of unchoking. We also validate our model through both simulations and experiments. The preliminary experimental results show that our model is significantly more accurate than existing ones.

In this paper, we conduct an in-depth study on the feasibility of using network coding to ameliorate the content availability of BitTorrent swarms. We first perform mathematical analysis on the potential improvement in the content availability and bandwidth utilization induced by two existing network coding schemes. It is found that these two coding schemes either incur a very high coding complexity and disk operation overhead or cannot effectively leverage the potential of improving the content availability. In this regard, we propose a simple sparse network coding scheme in which both the drawbacks mentioned before are precluded. To accommodate the proposed coding scheme into BitTorrent, a new block scheduling algorithm is also developed based on the original rarest-first block scheduling policy of BitTorrent. Through extensive simulations and performance evaluations, we show that the proposed coding scheme is very effective in terms of improving the content availability of BitTorrent swarms when compared with some existing methods.

Delivering content efficiently through biased neighbor selection has attracted a lot of researchers' attention in recent years. Meanwhile, how to help peers understand each other is a crucial precondition of biased neighbor selection in distributed P2P context. Recent researches have showed that reciprocation based schemes provide a feasible way of categorizing peers. These schemes can perform in direct or indirect ways. For example, tit-for-tat is a typical example of direct ways, while reputation-based schemes are the representative examples of indirect ways. Although tit-for-tat has been proved to be successful from practical deployment and academic studies, it still suffers from free-riding, malicious peers and other problems. On the other hand, reputation-based schemes pay little attention to malicious peers. However, in this paper we propose an approach to promote the whole system performance as well as cope with malicious peers. Firstly, by building a simple mathematical model for the content delivery process in BT-like system, we find that the delivery order is critical to system performance, after that we present the best selection policy from system and single peer's perspective respectively. Secondly, according to analysis results, we bring forward indirect reciprocate Reputation (iRep), detail the design issues and sketch security and overhead introduced by iRep. Finally, several simulation experiments are conducted to evaluate the performance of iRep through comparison with tit-for-tat and Eigentrust. The comparison results validate that iRep can efficiently promote system performance with limited overheads.

Features of online social networks are being introduced in various applications and environments, including tools supporting virtual teams and online collaboration in general. In fact, social networking has a large potential for easing collaboration, also across organizational boundaries. However, effective e-collaboration through social networks requires the development of open and interoperable systems, allowing people belonging to different organizations to create ties, reflecting real connections existing in daily activities. Attention has to be paid to identity management, for allowing users to develop their reputation consistently, and to privacy and confidentiality, for creating a more trustful environment and protecting freedom of expression. In this article, the authors propose a novel peer-to-peer system, named Blogracy, leveraging the large BitTorrent network. Its main distinguishing features are: (i) protection of users' identity and privacy, (ii) absence of central control over published content; (iii) interoperability with other systems; and (iv) low costs and scalability of the infrastructure.

Recently, the cyber terror is becoming more complicated, intelligent, and causing more damage. To react more effectively to the future cyber terrors, it will be necessary to anticipate new cyber terror techniques and devise the preventive measures for the possible vulnerabilities of the system before the hackers actually disable the system. This paper verified that the attacking technology on the new vulnerability can paralyze internet service of windows system and smart phone using Android OS. Finally, the routing packets are discarded before they reach the destination and the connection to the destination host cannot be established.

In order to identify P2P traffic quickly and accurately as early as possible, an early intelligent P2P traffic identification method(EIIC) is proposed, which uses the size of early three packets payload and server port number obtained from the TCP flow as flow feature and classifies the traffic based on C4.5 algorithm. The results show that EIIC satisfies the following conditions: extracted features used, training samples selected under the unbiased conditions, it can be adaptive to actual network conditions and early classify the Internet traffic into application among WEB, MAIL, BitTorrent and eMule categories efficiently and quickly.

BitTorrent has recently introduced LEDBAT, a novel application-layer congestion control protocol for data exchange. The protocol design assumes that network bottlenecks are at the access of the network, and that thus user traffic competes creating self-induced congestion. To relieve this phenomenon, LEDBAT is designed to quickly infer when self-induced congestion is approaching (by detecting relative changes of the one-way delay in the transmission path), and to react promptly by reducing the sending rate prior to the congestion occurrence. Previous work has however shown LEDBAT to be affected by a latecomer advantage, where newly arriving connections can starve already existing flows. In this work, we propose modifications to the congestion window update mechanism of LEDBAT that solve this issue, thus guaranteeing intra-protocol fairness and efficiency. Closed-form expressions for the stationary throughput and queue occupancy are provided via a fluid model, whose accuracy is confirmed by means of ns2 packet level simulations. Our results show that the proposed change can effectively solve the latecomer issue, furthermore without affecting the other original LEDBAT goals.

BitTorrent currently contributes a significant amount of inter-ISP traffic. This has motivated research and development to explore caching and locality-aware neighbor selection mechanisms for costly traffic reduction. Recent researches have analyzed the possible effects of caching BitTorrent traffic and have provided preliminary results on its cacheability. However, little is known about the specifics of caching design that affect cache effectiveness and operation, such as replacement policy and cache size. This study addresses this gap with a comprehensive analysis of BitTorrent caching based on traces of user behavior in four popular BitTorrent sites. Our trace-driven simulation results show differences in BitTorrent traffic caching compared to that of the Web and other peer-to-peer applications. Differently from Web and other peer-to-peer caching, larger caches are necessary to achieve similar caching effectiveness in BitTorrent traffic. Furthermore, in BitTorrent caching, the LRU replacement policy that takes the temporal locality into account shows the best performance. We also use a locality-aware neighbor selection mechanism as a baseline to evaluate the LRU caching effectiveness. We find that LRU caching can provide greater traffic reduction than locality-aware neighbor selection in several scenarios of cache size and number of ISP clients.

BitTorrent is one of the most successful peer-to-peer systems. Researchers have studied a number of aspects of the system, including its scalability, performance, efficiency and fairness. However, the complexity of the system has forced most prior analytical work to make a number of simplifying assumptions, for example, user homogeneity, or even ignore some central aspects of the protocol altogether, for example, the rate-based Tit-for-Tat (TFT) unchoking scheme, in order to keep the analysis tractable. Motivated by this, in this article we propose two analytical models that accurately predict the performance of the system while considering the central details of the BitTorrent protocol. Our first model is a steady-state one, in the sense that it is valid during periods of time where the number of users remains fixed. Freed by the complications of user time-dynamics, we account for many of the central details of the BitTorrent protocol and accurately predict a number of performance metrics. Our second model combines prior work on fluid models with our first model to capture the transient behavior as new users join or old users leave, while modelling many major aspects of BitTorrent. To the best of our knowledge, this is the first model that attempts to capture the transient behavior of many classes of heterogeneous users. Finally, we use our analytical methodology to introduce and study the performance of a flexible token-based scheme for BitTorrent, show how this scheme can be used to block freeriders and tradeoff between higher-bandwidth and lower-bandwidth users performance, and evaluate the scheme's parameters that achieve a target operational point.

BitTorrent is one of the popular P2P protocols to share files. In contrast to a traditional client–server application, all peers in a BitTorrent network participate in both downloading and uploading. Free-riding occurs when a peer intentionally tries to avoid uploading, but still downloads from the rest of the peers. Such a free-riding peer, or free-rider, hurts the overall system to its own benefit. Though there are mechanisms to discourage free-riding in the BitTorrent protocol, the protocol can be exploited by free-riders. In this paper we propose an alternative strategy called the demerit point strategy as an extension to what the protocol already offers, and show through experimental evidence that this strategy is highly effective in mitigating free-riding. We compare the new strategy against a similar recent extension, and through experimental evidence, establish that our strategy is better.

Peer-to-Peer (P2P) plays an important role in the domain of Internet application, such as file sharing and instance communication. However, for the characteristic of bandwidth-intensive, P2P traffic identification is especially important in network management, which has been a hot topic in recent years. Based on the review of shortages of current existed technologies, a k-means algorithm based method was brought forward to identify the P2P traffic. For the reason that K-Means is one of the quickest and simplest clustering methods, it was selected as the core algorithm. In addition, the process of flow-information extraction and the descriptions of selected traffic attribute were also introduced in detail. Since the BT file-sharing traffic mainly runs over TCP, we only extract the flow-information of TCP connections. Finally, the experiments on 3 common used P2P applications, which are BitTorrent, BitSpirit and eMule, demonstrated the validity and efficiency of the method.

Peer-to-peer networks' widespread use makes multimedia files available to users worldwide. However, such networks are often used to spread illegal material while the data source and acquiring users remain anonymous. This article analyzes activity measurements in the BitTorrent network and examines child sex abuse activity through three major BitTorrent Web portals.

Private BitTorrent community is becoming increasingly popular, and generates a huge amount of Internet traffic. In this paper, we present a thorough measurement study on a famous private BitTorrent community, CHDBits. We find that the content of torrents published in this community are highly available, although many torrents may have been released for a very long time, and we also obtain that users in most torrents could download at a high rate. By studying user profiles, we show that many users have participated in multiple torrents, thereby generating a great amount of upload and download traffic. The user profiles also reveal that almost all users maintain a high share ratio, and are willing to contribute to content distribution by spending more time in seeding than in leeching (downloading). Our study suggests that the bandwidths of a user have a significant impact on their behavior. Low bandwidth users are more likely to participate in the torrents with a smaller content size or a higher popularity; compared with low bandwidth users, high bandwidth users tend to participate in more torrents, but spend much less time in seeding.

The enormous popularity of Video on Demand (VoD) has attracted substantial research attention into the effective use of peer-to-peer (P2P) architectures to provide solutions at large-scale. In particular, the high efficiency of BitTorrent has inspired many P2P protocols for VoD. However, these protocols use different approaches to adapt the design of Bittorrent to VoD, and in most cases their performance has been evaluated separately and in limited scenarios. As a consequence, the research community still lacks a clear understanding of how these protocols compare against each other and how well each of them would work in real world conditions, where, for instance, peers have heterogeneous bandwidths, may freeride or may be located behind NAT/firewall. In this paper, we propose a simulation based methodology which aims at putting forward a common base for comparing the performance of these different protocols under a wide range of conditions. We show that, despite their considerable differences: (i) existing BitTorrent-like VoD approaches all share some characteristics, such as that their bandwidth reciprocity based methods to incentivize cooperation do not always yield an optimal overall performance. Furthermore, we demonstrate that (ii) in these protocols there is a trade-off between QoS and resilience to freeriding and malicious attacks. We also discover that, (iii) when peers doing streaming coexist with peers doing traditional file transfer, the latter actually benefit from this coexistence, at the expenses of the former. Finally, we show that (iv) early departures of peers from the system do not significantly affect the QoS delivered, while jumping to a different position in the file has a bigger negative impact. Overall, our findings provide important implications for both VoD service providers and future system designers. On the one hand, our results can guide VoD service providers in selecting the most appropriate protocol for a given environment. On the other hand, exposing the flaws of current approaches will help researchers in improving them and/or designing better ones.

Peer-to-peer file sharing systems, most notably BitTorrent (BT), have achieved tremendous success among Internet users. Recent studies suggest that the long-term relationships among BT peers can be explored to enhance the downloading performance; for example, for re-sharing previously downloaded contents or for effectively collaborating among the peers. However, whether such relationships do exist in real world remains unclear. In this paper, we take a first step towards the real-world applicability of peers' long-term relationship through a measurement based study. We find that 95% peers cannot even meet each other again in the BT networks; therefore, most peers can hardly be organized for further cooperation. This result contradicts to the conventional understanding based on the observed daily arrival pattern in peer-to-peer networks. To better understand this, we revisit the arrival of BT peers as well as their long-range dependence. We find that the peers' arrival patterns are highly diverse; only a limited number of stable peers have clear self-similar and periodic daily arrivals patterns. The arrivals of most peers are, however, quite random with little evidence of long-range dependence. To better utilize these stable peers, we start to explore peers' long-term relationships in specific swarms instead of conventional BT networks. Fortunately, we find that the peers in Twitter-initialized torrents have stronger temporal locality, thus offering great opportunity for improving their degree of sharing. Our PlanetLab experiments further indicate that the incorporation of social relations remarkably accelerates the download completion time. The improvement remains noticeable even in a hybrid system with a small set of social friends only.

FrostWire is a peer-to-peer (P2P) application derived from the open source code of Limewire. Frostwire was first released in February of 2005 as a Gnutella P2P client. As interest in the Gnutella network waned, FrostWire switched in later versions to becoming a torrent client. Since the United States government shut Limewire down, FrostWire has become more popular and is seen more often in criminal investigations. This paper describes the different components of FrostWire and the useful information which can be obtained in a digital forensic examination.

With BitTorrent, efficient peer upload utilization is achieved by splitting contents into many small pieces, each of which may be downloaded from different peers within the same swarm. Unfortunately, piece and bandwidth availability may cause the file-sharing efficiency to degrade in small swarms with few participating peers. Using extensive measurements, we identified hundreds of thousands of torrents with several small swarms for which reallocating peers among swarms and/or modifying the peer behavior could significantly improve the system performance. Motivated by this observation, we propose a centralized and a distributed protocol for dynamic swarm management. The centralized protocol (CSM) manages the swarms of peers at minimal tracker overhead. The distributed protocol (DSM) manages the swarms of peers while ensuring load fairness among the trackers. Both protocols achieve their performance improvements by identifying and merging small swarms and allow load sharing for large torrents. Our evaluations are based on measurement data collected during eight days from over 700 trackers worldwide, which collectively maintain state information about 2.8 million unique torrents. We find that CSM and DSM can achieve most of the performance gains of dynamic swarm management. These gains are estimated to be up to 40% on average for small torrents.

Content sharing has emerged as a popular application in Peer-to-Peer (P2P) networks. The increasing number of free-riders and untrustworthy peers in content sharing network reduces the credibility of the shared contents. Also, the malicious peers pose the danger of security violation and bandwidth wastage by sharing polluted or infected contents in the network for their personal benefits. In this paper, we propose a unified trust management strategy by combining trust and security models with reputation based preferences for efficient content sharing in P2P networks. The problems in P2P content sharing, like free-riding, content pollution, content poisoning, peer availability, content availability, DoS attack, and flash crowd are considered in our unified trust management model. The model provides controlled scalability of the overlay network, and concurrently ensures the availability of contents for longer time in the network. The provider initiating content sharing is protected from Denial-of-Service (DoS) attack through restricted network size and interspersing the provider within a set of distributed peers. Performance measures, such as scalability, content availability, flash crowd and prevention of polluted or infected content distribution are compared with BitTorrent in heterogeneous environment. The advantage of this model is that it can be deployed easily in BitTorrent-like P2P networks. Simulation results show that controlled scalability helps in efficient utilization of bandwidth and protection for the providers, ultimately ensuring trust on the P2P network and the content shared.

In recent years, the surge of large-scale peer-to-peer (P2P) applications has brought huge amounts of P2P traffic, which has significantly changed the Internet traffic pattern and increased the traffic-relay cost at the Internet Service Providers (ISPs). To alleviate the stress on networks, methods of localized peer selection have been proposed that advocate neighbor selection within the same network (AS or ISP) to reduce the cross-ISP traffic. Nevertheless, localized peer selection may potentially lead to the downgrade of download speed at the peers, rendering a non-negligible tradeoff between the download performance and traffic localization in the P2P system. Aiming at effective peer selection strategies that achieve any desired Pareto optimum in face of the tradeoff, our contributions in this paper are three-fold: (1) We characterize the performance and locality tradeoff as a multi-objective $b$ -matching optimization problem. In particular, we first present a generic weighted $b$ -matching model that characterizes the tit-for-tat in BitTorrent-like peer selection. We then introduce multiple optimization objectives into the model, which effectively characterize the performance and locality tradeoff using simultaneous objectives to optimize. (2) We design fully distributed peer selection algorithms that can effectively approximate any desired Pareto optimum of the global multi-objective optimization problem, which represents a desired tradeoff point between performance and locality in the entire system. (3) Taking network dynamics into consideration, we further propose practical protocols that allow each peer to dynamically adjust its peer selection preference on download performance or traffic locality, in order to adapt to the current quality of peering connections, while guaranteeing that the desired tradeoff is still achieved over its entire download process. To support our models and protocols, we have conducted rigorous analysis, extensive simulations, and prototype experiments under various practical settings extracted from real-world traces.

Current approaches to build social networking systems are based on a centralized architecture because it allows a simple browser-based user experience and makes easier and more efficient to implement many algorithms used in a social networking site (e.g., friend suggestion), However this kind of architecture has many drawbacks for its users, e.g., lack of privacy, lack of anonymity, risks of censorship and operating costs. This paper presents a system, called Blogracy, which uses widespread and stable peer-to-peer technologies, such as distributed hash tables and BitTorrent, for coping with intrinsic defects of centralized architectures and for being the basis of solid distributed social networking platforms. Moreover, Blogracy takes advantages of multi-agent systems for simplifying the implementation of social network services in a decentralized setting.

Peer-to-Peer (P2P) communications and its applications have become conventional architecture in the wired network environment. However, they have not been effectively adapted to the ensemble mobile environment which composed of various devices such as smart mobiles devices, laptops, and device with embedded software. In P2P systems, each node can act as a client and as a server at the same time and shares with others its own data. Our contribution consists in designing, implementing and testing a BitTorrent like application adapted to wireless ad-hoc networks of Android Mobile Phones. The employment of P2P protocols and applications in the platform of the ensemble mobile environment is becoming a promising solution which permits a wide number of users to share their own contents (data, audio, video, etc.) and communicate with each other without using costly and centralized network infrastructure. By using a central server, the peers will be able to get the information about the contents of other peers. Even in the absence of the Internet, the mobile devices provide users with the potential opportunity to connect in ad-hoc manner via short range wireless protocol such as Wi-Fi. Keywords- Peer to peer computing, mobile ad hoc networks, wireless communication, Wi-Fi, multimedia communication.

Analyzing and modeling of the BitTorrent (BT) resource popularity and swarm evolution is important for better understanding current BT system and designing accurate BT simulators. Although lots of measurement studies on BT almost cover each important aspect, little work reflects the recent development of BT system. In this paper, we develop a hybrid measurement system incorporating both active and passive approaches. By exploiting DHT (Distribute Hash Table) and PEX (Peer Exchange) protocols, we collect more extensive information compared to prior measurement systems. Based on the measurement results, we study the resource popularity and swarm evolution with different population in minute/ hour/day scales, and discover that: 1) the resources in BT system appear obvious unbalanced distribution and hotspot phenomenon, in that 74.6% torrents have no more than 1000 peers; 2) The lifetime of torrents can be divided into a fast growing stage, a dramatically shrinking stage, a sustaining stage and a slowly fading out stage in terms of swarm population; 3) Users’ interest and diurnal periodicity are the main factors that influence the swarm evolution. The former dominates the first two stages, while the latter is decisive in the third stage. We raise an improved peer arrival rate model to describe the variation of the swarm population. Comparison results show that our model outperforms the state-of-the-art approach according to root mean square error and correlation coefficient.

Peer-to-Peer (P2P) communications and its applications have become conventional architecture in the wired network environment. However, they have not been effectively adapted to the ensemble mobile environment which composed of various devices such as smart mobiles devices, laptops, and device with embedded software. In P2P systems, each node can act as a client and as a server at the same time and shares with others its own data. Our contribution consists in designing, implementing and testing a BitTorrent like application adapted to wireless ad-hoc networks of Android Mobile Phones. The employment of P2P protocols and applications in the platform of the ensemble mobile environment is becoming a promising solution which permits a wide number of users to share their own contents (data, audio, video, etc.) and communicate with each other without using costly and centralized network infrastructure. By using a central server, the peers will be able to get the information about the contents of other peers. Even in the absence of the Internet, the mobile devices provide users with the potential opportunity to connect in ad-hoc manner via short range wireless protocol such as Wi-Fi.

We propose a BitTorrent-like protocol based on an online learning (reinforcement learning) mechanism, which can replace the peer selection mechanisms in the regular BitTorrent protocol. We model the peers' interactions in the BitTorrent-like network as a repeated stochastic game, where the strategic behaviors of the peers are explicitly considered. A peer that applies the reinforcement learning (RL)-based mechanism uses the observations on the associated peers' statistical reciprocal behaviors to determine its best responses and estimate the corresponding impact on its expected utility. The policy determines the peer's resource reciprocations such that the peer can maximize its long-term performance. We have implemented the proposed mechanism and incorporated it into an existing BitTorrent client. Our experiments performed on a controlled Planetlab testbed confirm that the proposed protocol 1) promotes fairness and provides incentives to contributed resources, i.e., high capacity peers improve their download completion time by up to 33 percent, 2) improves the system stability and robustness, i.e., reduces the peer selection fluctuations by 57 percent, and (3) discourages free-riding, i.e., peers reduce their uploads to free-riders by 64 percent as compared to the regular BitTorrent protocol.

We conduct a detailed simulation study to examine how localizing P2P traffic within network boundaries impacts the profitability of an ISP. A distinguishing aspect of our work is the focus on Internet-wide implications, i.e., how adoption of localization within an ISP affects both itself and other ISPs. Our simulations are based on detailed models that estimate inter-autonomous system (AS) P2P traffic and inter-AS routing, localization models that predict the extent to which P2P traffic is reduced, and pricing models that predict the impact of changes in traffic on the profit of an ISP. We evaluate our models by using a large-scale crawl of BitTorrent containing over 138 million users sharing 2.75 million files. Our results show that the benefits of localization must not be taken for granted. Some of our key findings include: 1) residential ISPs can actually lose money when localization is employed, and some of them will not see increased profitability until other ISPs employ localization; 2) the reduction in costs due to localization will be limited for small ISPs and tends to grow only logarithmically with client population; and 3) some ISPs can better increase profitability through alternate strategies to localization by taking advantage of the business relationships they have with other ISPs.

Personal cloud storage systems, like Dropbox, are revolutionizing the way people think about and access their files. As the prevailing model, these systems use unicast to push file changes to each of the "unsynced" devices. And as a result, they transmit multiple times the same information, once per unsynced device. This puts an unnecessary strain on outgoing bandwidth at the datacenters. One way to address this is to leverage P2P-like content distribution to benefit from user resources at the edges of the Internet. Although protocols like BitTorrent have proven to be effective in this scenario, we go a step further in this work and propose cross-swarm bundling as a mechanism for file distribution. One key contribution of this work is that, instead of using bundling as means to extend the lifetime of swarms, we show that it can be useful to improve the Quality of Experience (QoE). We validate our proposal using a trace of Ubuntu One, a real personal cloud system, obtaining significant improvements on the QoE levels.

Tactical Edge Networks are one of the most challenging communication environments, where node mobility, constrained devices, and the wide use of wireless ad hoc channels for communications cause frequent link disruption and network partitioning. Additionally, applications running in Tactical Edge Networks often follow one-to-many and many-to-many communication models that require the nodes' cooperation to enable data delivery. Many studies proposed the use of peer-to-peer systems in mobile ad hoc networks to remove any dependency on centralized nodes and to cope with link disruptions and network partitioning phenomena that derive from the extreme dynamicity of Tactical Edge Networks. In this paper, we compare the performance of file sharing in mobile ad hoc networks using an implementation of the BitTorrent peer-to-peer protocol and DisService, a middleware for information dissemination specifically designed for Tactical Edge Networks. DisService supports applications with routing and peer-to-peer content delivery in mobile ad hoc networks. We ran several experiments in an emulated environment to evaluate the performance of each solution when sharing large files. The obtained results show that TEN-specific solutions such as DisService can outperform traditional peer-to-peer solutions like BitTorrent.

Natural disasters take its toll on traditional communication infrastructure severely causing intermittent network connectivity due to partially or fully damaged communication infrastructure. Therefore, data dissemination is hampered and the volunteers and different disaster management agencies find it difficult to communicate among them. Fortunately, a sizeable population (around 35%–45%) these days owns various wireless devices like smart phones, tablets etc. with multiple communication interfaces (Bluetooth, Wi-Fi Direct). These devices with their alternative communication capabilities can be harnessed in a disaster aftermath in order to disseminate situational information. However, the procedure to disseminate such information through these devices should be simple enough so that minimal technical expertise is required from the user end. Several Android based applications are available which offers data forwarding service based on Wi-Fi direct. All such applications provide only unicast mode of communication while lacking to provide multicast and broadcast services. In this paper we provide a complete solution Disaster Messenger, an Android based application which allows the volunteers to disseminate information in absence of network infrastructure (through Wi-Fi direct) in unicast, multicast and broadcast mode. We perform rigorous field experiments to evaluate the performance of Disaster Messenger by varying movement speeds of the nodes and distance between the nodes. We also evaluate its performance in terms of energy efficiency. The comparison of the Disaster Messenger with a couple of well-known file sharing applications namely SHAREit and BitTorrent Sync reveals that Disaster Messenger outperforms SHAREit and BitTorrent Sync in terms of energy efficiency and data transfer rate in unicast mode. Due to unavailability of any competing application which supports multicast and broadcast services, we have not been able to compare the performance of our application for the said services.

Peer-to-peer (p2p) koristi koncept umrežavanja raĉunala u kojem nema servera tj. poslužitelja, svako je raĉunalo i server i klijent. U takvoj mreži korisnici razmjenjuju datoteke meĊusobno i to će se prikazati na konkretnim primjerima, u našem primjeru preko uTorrent klijenta. Prolaze se osnovne stvari po pitanju p2p mreža, od podjele do nekih osnovnih karakteristika. Govori se o BiTtorrent protokolu, obraĊuje se princip rada i daljnja implementacija p2p mreža. U ovom završnom radu koristi se Wireshark alat za praćenje i analizu mrežnih podataka, posebice BitTorrent protokola. Peer-to-peer ( P2P ) uses the concept of networking computers in which has no server. Each computer is a server and a client. In such network, users exchange files with each other and this will show through concrete examples, in our example over the uTorrent client. We pass the basic things in terms of P2P networks, from distribution to some basic characteristics. We are talking about the BitTorrent protocol, process operating principle and further implementation of P2P networks. In this final work we use Wireshark tool for monitoring and analyzing network data, in particular the BitTorrent protocol.

This paper addresses the problem of building and maintaining image repositories which form the basis for world-scale visual models. The availability of these models enable capabilities such as visual localization, persistent surveillance, and structure from motion. We approach this problem through the creation of PeerAppear, a location-aware framework for extensible image annotation and peer-to-peer dissemination. Due to the dynamic nature of the world, solutions to this problem generally require significant effort to be spent on mapping. PeerAppear enables a decentralized solution through the implementation of a peer-to-peer middleware framework which automates the indexing and sharing of visual information extracted from images in a user's collection. The PeerAppear network achieves scale through a Bittorrent style overlay network, which indexes the locations of user's image collections using a hierarchical geographic segmentation scheme in a distributed hash table. By enabling a distributed and collaborative solution, network participants are able to provide for frequent remapping and a search capability which leverages efficient and effective visual representations. The framework was implemented in Python and evaluated using Raspberry Pi computers for data collection and a workstation computer to simulate network participants. This evaluation showed that the framework was able to provide an effective image search capability and shows promise for large-scale operations.

In this study, we focused on peer-to-peer protocols (P2P), which represent a promising solution for data dissemination and content delivery at low-cost in the Internet. We performed, initially, a behavioral study of various P2P protocols for file sharing (content distribution without time constraint) and live streaming. Concerning file sharing, we have shown the impact of Hadopi on users’ behavior and discussed the effectiveness of protocols according to content type, based on users’ choice. BitTorrent appeared as the most efficient approach during our study, especially when it comes to large content. As for streaming, we studied the quality of service of Sopcast, a live distribution network that accounts for more than 60% of P2P broadcast live events. Our in-depth analysis of these two distributionmodes led us to focus on the BitTorrent protocol because of its proven efficiency in file sharing and the fact that it is open source. In the second part of the thesis, we proposed and implemented a new protocol based on BitTorrent, in a controlled environment. The modifications that we proposed allow to increase the efficiency of the protocol through improved dissemination of metadata (the rarest piece), both for live and file sharing. An enhanced version is introduced with a push method, where nodes that lag behind receive an extra service so as to improve the overall performance; Dans cette thèse, nous nous sommes intéressés aux protocoles pair-à-pair (P2P), qui représentent une solution prometteuse pour la diffusion et le partage de données à faible coût sur Internet. Nous avons mené, dans un premier temps, une étude comportementale de différents protocoles P2P pour le partage de fichier (distribution de contenus sans contrainte de temps) puis le live. Dans la première étude centréesur le partage de fichier, nous avons montré l’impact d’Hadopi sur le comportement des utilisateurs et discuté l’efficacité des protocoles en fonction du contenu et l’efficacité protocolaire, en se basant sur les choix des utilisateurs. BitTorrent s’est nettement démarqué au cours de cette étude, notamment pour les grands contenus. En ce qui concerne le live, nous nous sommes intéressés à la qualité de servicedu réseau de distribution live Sopcast, car plus de 60% des événements live diffusés en P2P le sont sur ce réseau. Notre analyse approfondie de ces deux modes de distribution nous a fait nous recentrer sur BitTorrent, qui est à la base de tous les protocoles P2P Live, et est efficace en partage de fichier et complètement open source. Dans la seconde partie de la thèse, nous avons proposé et implémenté dansun environnement contrôlé un nouveau protocole sur la base de BitTorrent avec des mécanismes protocolaires impliquant tous les pairs dans la gestion du réseau. Ces nouveaux mécanismes permettent d’augmenter l’efficacité du protocole via une meilleure diffusion, tant pour le live que le partage de fichier, de métadonnées (la pièce la plus rare) et via une méthode dite de push, par laquelle un client va envoyer du contenu aux pairs les plus dans le besoin

Networks rely on broadcasts and multicasts for some of the most basic services such as auto-configuration. In the recent past, application layer protocols have increasingly made use of the broadcast mechanism. Examples of these applications include Dropbox, Spotify or BitTorrent Sync. Given that broadcasts can be seen by every device in a broadcast domain, information that can be gleaned from this traffic is trivially accessible by a passive observer. Therefore, an obvious question is: what does broadcast and multicast traffic reveal about a device, a user or a group in a network?

This paper presents initial development in the search for alternative strategies for agent-based distributed control algorithms based on decoupling time-critical operations from the bulk of inter-agent communication. Agents retain autonomy from any central authority; each maintains a global view of the system and solves the global problem locally, reducing the need for communication during time-critical operations. Global data pre-fetching can be relegated to a more relaxed schedule similar to that of energy dispatch, where communication link reliability and bandwidth are much easier to manage. Depending on the size of the system as well as the speed and reliability of the communication links, such strategies might provide better performance and reliability than agent-local view strategies. An agent-based test bed setup and an example of a power flow solver are presented.

Although Mainline DHT is not an official BitTorrent protocol so far, it's widely used in many BitTorrent clients such as Utorrent, Vuze, BitComet and Xunlei. Despite there are millions of Mainline DHT users, only little research focus on Mainline DHT. In this paper, we present two kinds of measurement results based on crawling Mainline DHT. Firstly, we develop an effective crawler and crawl Mainline DHT over 10 days. We collected 10,149,649 magnet links and received over 264,846,482 get_peers requests from 57,065,499 unique peers. Based on the measurement results, we found that: (1) Russian and China play dominant roles in Mainline DHT which contribute 35% peers in it, and there are 5% Internet users use Mainline in Europe, (2) UTorrent is the most popular clients so far, half of peers use it. (3) We found that most clients use randomly chosen port numbers, only 8.9% use constant port. (4) Zona is a popular Russia peer to peer client, nine in ten top popular magnet links are unique in Zone, and only one is BitTorrent magnet link. (5) The peers' size of torrent almost follows a Zipf distribution. 11% torrents take up 95% peers of the total. 46% torrents only get one peer during our experiment. Secondly, we study two ways to convert magnet link to torrent file: Converting by five popular torrent storage services and converting by Extension protocol. We compare the performance of them in terms of converting rate, converting time, advantages and disadvantages and discover that: (1) The converting rate of torrent storage services and Extension protocol are 46.9% and 22.7%. (2) The average successful converting time of Extension protocol is 75s, and if a magnet spends more than 150s to convert but still couldn't get good peers, it tends to convert unsuccessfully at present. The best scheme is stopping for a while, and waiting good peers on line. (3) NAT is the main reason caused the converting or downloading failure, there are 32.5% peers stay in NAT or firewall. The best solution of NAT user is the popularized of IPv6 or Tunneling. Understanding DHT in depth can improve the performance of current DHT system.

Once pervasive, the File Transfer Protocol (FTP) has been largely supplanted by HTTP, SCP, and BitTorrent for transferring data between hosts. Yet, in a comprehensive analysis of the FTP ecosystem as of 2015, we find that there are still more than 13~million FTP servers in the IPv4 address space, 1.1~million of which allow "anonymous" (public) access. These anonymous FTP servers leak sensitive information, such as tax documents and cryptographic secrets. More than 20,000 FTP servers allow public write access, which has facilitated malicious actors' use of free storage as well as malware deployment and click-fraud attacks. We further investigate real-world attacks by deploying eight FTP honeypots, shedding light on how attackers are abusing and exploiting vulnerable servers. We conclude with lessons and recommendations for securing FTP.

A major problem in virtualized cloud datacenters today is the inefficiency of communication between virtual machines, i.e. inter-VM communication. Efforts have gone into optimizing communication between VMs present on the same physical server in the cloud, i.e. co-resident or co-located VMs; however, optimizing communication between VMs present on different physical servers is a separate issue. As these communicate via the TCP/IP network stack, improvements in performance or efficiency are normally proposed by customizations to the communication protocols requisite to the datacenter. We propose a mechanism to increase the average speed of inter-VM file distribution in the cloud for VMs on separate physical servers by implementing a BitTorrent-like peer-to-peer (P2P) system. The proposal, named VirtTorrent, uses direct communication between VMs in the cloud to implement a protocol similar to BitTorrent, allowing files to be distributed swiftly and with minimal network congestion. As inter-VM communication and network congestion are both important issues in the datacenter, we believe that VirtTorrent can make a marked improvement in the scenarios laid out in this paper.

As ISPs face IPv4 address scarcity they increasingly turn to network address translation (NAT) to accommodate the address needs of their customers. Recently, ISPs have moved beyond employing NATs only directly at individual customers and instead begun deploying Carrier-Grade NATs (CGNs) to apply address translation to many independent and disparate endpoints spanning physical locations, a phenomenon that so far has received little in the way of empirical assessment. In this work we present a broad and systematic study of the deployment and behavior of these middleboxes. We develop a methodology to detect the existence of hosts behind CGNs by extracting non-routable IP addresses from peer lists we obtain by crawling the BitTorrent DHT. We complement this approach with improvements to our Netalyzr troubleshooting service, enabling us to determine a range of indicators of CGN presence as well as detailed insights into key properties of CGNs. Combining the two data sources we illustrate the scope of CGN deployment on today's Internet, and report on characteristics of commonly deployed CGNs and their effect on end users. TRUE pub

Cybercrime and related malicious activity in our increasingly digital world has become more prevalent and sophisticated, evading traditional security mechanisms. Digital forensics has been proposed to help investigate, understand and eventually mitigate such attacks. The practice of digital forensics, however, is still fraught with various challenges. Some of the most prominent of these challenges include the increasing amounts of data and the diversity of digital evidence sources appearing in digital investigations. Mobile devices and cloud infrastructures are an interesting specimen, as they inherently exhibit these challenging circumstances and are becoming more prevalent in digital investigations today. Additionally they embody further characteristics such as large volumes of data from multiple sources, dynamic sharing of resources, limited individual device capabilities and the presence of sensitive data. These combined set of circumstances make digital investigations in mobile and cloud environments particularly challenging. This is not aided by the fact that digital forensics today still involves manual, time consuming tasks within the processes of identifying evidence, performing evidence acquisition and correlating multiple diverse sources of evidence in the analysis phase. Furthermore, industry standard tools developed are largely evidence-oriented, have limited support for evidence integration and only automate certain precursory tasks, such as indexing and text searching. In this study, efficiency, in the form of reducing the time and human labour effort expended, is sought after in digital investigations in highly networked environments through the automation of certain activities in the digital forensic process. To this end requirements are outlined and an architecture designed for an automated system that performs digital forensics in highly networked mobile and cloud environments. Part of the remote evidence acquisition activity of this architecture is built and tested on several mobile devices in terms of speed and reliability. A method for integrating multiple diverse evidence sources in an automated manner, supporting correlation and automated reasoning is developed and tested. Finally the proposed architecture is reviewed and enhancements proposed in order to further automate the architecture by introducing decentralization particularly within the storage and processing functionality. This decentralization also improves machine to machine communication supporting several digital investigation processes enabled by the architecture through harnessing the properties of various peer-to-peer overlays. Remote evidence acquisition helps to improve the efficiency (time and effort involved) in digital investigations by removing the need for proximity to the evidence. Experiments show that a single TCP connection client-server paradigm does not offer the required scalability and reliability for remote evidence acquisition and that a multi-TCP connection paradigm is required. The automated integration, correlation and reasoning on multiple diverse evidence sources demonstrated in the experiments improves speed and reduces the human effort needed in the analysis phase by removing the need for time-consuming manual correlation. Finally, informed by published scientific literature, the proposed enhancements for further decentralizing the Live Evidence Information Aggregator (LEIA) architecture offer a platform for increased machine-to-machine communication thereby enabling automation and reducing the need for manual human intervention.

Docker, a container-based virtualization technology, is widely used in datacenters. To increase the speed of booting containers, the storage and the distribution of Docker images have received much research effort. There are also some efforts which use Peer-to-Peer file downloading method to speed-up Docker image distribution. However, these systems just package image as a file for sharing without considering the layering structure of the Docker image. To increase the booting speed of Docker image, in this work, we propose an efficient Hybrid Docker Image Distribution System for Datacenters (HDID). First, to gain insight into the layer structure of Docker images, we investigate the size distribution of the top 29 popular Docker image layers. Second, based on the study of the size distribution, we introduce a hybrid distribution method which adaptively uses both the BitTorrent protocol, a P2P file downloading technique, and the original Registry downloading technique to boost the image transferring procedure. Third, as the BitTorrent protocol is designed for the Internet instead of datacenter networks, to further reduce the booting time, we develop file-downloading strategy, which optimizes BitTorrent for Docker images in datacenter networks. Finally, through extensive experiments, we show that the proposed method can reduce the image distribution time of Docker by about 90% compared to the default Docker image distribution method.

International audience; When considering to passively collect and then process network traffic traces, the need to analyze raw data at several Gbps and to extract higher level indexes from the stream of packets poses typical BigData-like challenges. In this paper, we engineer a methodology to extract, collect and process passive traffic traces. In particular, we design and implement analytics that, based on a filtering process and on the building of empirical distributions, enable the comparison between two generic collections, e.g., data gathered from two different vantage points, from different populations, or at different times. The ultimate goal is to highlight statistically significant differences that could be useful to flag to incidents for the network manager.After introducing the methodology, we apply it to assess the impact of Carrier-Grade NAT (CGN), a technology that Internet Service Providers (ISPs) deploy to limit the usage of expensive public IP addresses. Since CGN may introduce connectivity issues and performance degradation, we process a large dataset of passive measurements collected from an ISP using CGN for part of its customers. We first extract detailed per-flow information by processing packets from live links. Then, we derive higher level statistics that are significant for the end-users, e.g., TCP connection setup time, HTTP response time, or BitTorrent average download throughput. At last, we contrast figures of customers being offered public or private addresses, and look for statistically significant differences. Results show that CGN does not impair quality of service in the analyzed ISP deployment. In addition, we use the collected data to derive useful figures for the proper dimensioning of the CGN and the configuration of its parameters in order to avoid impairments on end-users’ experience.

DOI: 10.1016/j.jnca.2016.02.006 Filiació URV: SI Users are unceasingly relying on personal clouds (like Dropbox, Box, etc) to store, edit and retrieve their files stored in remote servers. These systems generally follow a client–server model to distribute the files to end-users. This means that they require a huge amount of bandwidth to meet the requirements of their clients. Personal clouds with limited bandwidth budget can benefit from the upload speed of the clients interested in the same content to improve the quality of service. This can be done by introducing a peer-to-peer protocol, BitTorrent for instance, when the load on a certain content becomes high. The main challenge is to decide when to switch to BitTorrent and how to allocate the cloud's available bandwidth to the different clients. In this paper, we propose an algorithm for the allocation of the cloud׳s bandwidth. Based on the current load and the predefined quality of service constraints, the algorithm identifies the most suitable protocol for each swarm and provides the corresponding bandwidth allocation. We validate the algorithm using a real trace of the Ubuntu One system and the results show important gains in the download times experienced by the clients.

Modern genomic studies utilize high-throughput instruments which can produce data at an astonishing rate. These big genomic datasets produced using next generation sequencing (NGS) machines can easily reach peta-scale level creating storage, analytic and transmission problems for large-scale system biology studies. Traditional networking protocols are oblivious to the data that is being transmitted and are designed for general purpose data transfer. In this paper we present a novel data-aware network transfer protocol to efficiently transfer big genomic data. Our protocol exploits the limited alphabet of DNA nucleotide and is developed over the hypertext transfer protocol (HTTP) framework. Our results show that proposed technique improves transmission up to 84 times when compared to normal HTTP encoding schemes. We also show that the performance of the resultant protocol (called VTTP) using a single machine is comparable to BitTorrent protocol used on 10 machines.

1969. godine američko Ministarstvo obrane osniva internet pod nazivom ARPANET, mrežu koja je za cilj imala povezati računala diljem države kako bi se država eventualno mogla obraniti od nuklearnih projektila Rusije u doba Hladnog rata.[1] 1991. godine britanski znanstvenik Tim Berners Lee predstavlja World Wide Web (WWW), najpopularniju uslugu interneta. 1992. godine američki kongres donosi odluku da se web smije koristiti u komercijalne svrhe, što značajno ubrzava razvoj web tehnologija i aplikacija sljedećih godina. U periodu od 1995. do 2001. godine aktualan je tzv. „web 1.0“ model koji počiva na jednosmjernoj komunikaciji između webmastera i posjetitelja web mjesta. Propašću mnogih tzv. „dot-com“ tvrtki tijekom 2001. godine uviđa se potreba za novim modelom komunikacije koji bi ponovo oživio web ekonomiju. Postupno se razvija "web 2.0" model koji počiva na socijalizaciji, kolaboraciji i dvosmjernoj komunikaciji, odnosno interakciji između posjetitelja i web mjesta. Nastaju brojne moderne aplikacije poput društvenih mreža, blogova, portala te servisa za razmjenu sadržaja, čime je web postupno postao interaktivna multimedijska platforma. Spomenute promjene odnose se na principe razvoja web aplikacija, no infrastruktura i protokoli razmjene podataka nisu se mijenjali.[2,4] Web stranice pohranjene su na centralnom poslužitelju, a sadržaji se isporučuju korisnicima na zahtjev, po načelima HTTP protokola. Web mjesta u takvom okruženju ranjiva su na hakerske napade (npr. DDOS, XSS) i ograničena su hardverskim resursima poslužitelja, što utječe na brzinu izvršavanja i dostupnost sadržaja. 2008. godine započinje trend decentralizacije internet usluga. Nepoznata osoba ili grupa pod nazivom Satoshi Nakamoto javno objavljuje koncept decentralizirane valute BitCoin, bazirane na inovativnoj decentraliziranoj bazi podataka (BlockChain) te kriptografskim metodama osiguranja mreže. Na temeljima BitTorrent protokola i BitCoin tehnologije razvijen je ZeroNet. To je prva decentralizirana mreža u kojoj se web stranice razmjenjuju isključivo između korisnika, prema tzv. "peer-to-peer" principu. U takvom okruženju ne postoji centralni poslužitelj pa stoga na takvoj mreži nije moguće izvršavati aplikacije izrađene pomoću tzv. "server-side" tehnologija (npr. PHP, MySQL). ZeroNet trenutno podržava samo statične HTML stranice. Obzirom da je krajnji rezultat izvršavanja "server-side" tehnologija uvijek HTML dokument, one se mogu iskoristiti kao generatori HTML stranica za objavu u decentraliziranoj mreži. Ovaj završni rad će prikazati kako se lokalno instalirana WordPress CMS platforma može koristiti kao generator statičnih HTML stranica koje će se potom objaviti u ZeroNet mreži.[2,9,10,11]

The paper presents the results of the traffic investigation on the home networks for BitTorrent, Skype and M2M services. The traffic features are investigated on the test beds. One of them is created for Skype and BitTorrent traffic investigation. Another test bed is created for M2M traffic investigation. The related works on the teletraffic investigation area are analysed. The Poisson and self-similar traffic models are considered, including Skype and BitTorrent traffic models. The anti-persistent traffic models for M2M traffic in case of mass events is discussed. The anti-persistent traffic can mainly affect the traffic service. So, the most important task of the paper investigation is the detection of anti-persistent traffic on the home networks. The Hurst parameter is calculated by the analysis of change in dispersion method. The obtained results have shown that outcoming and incoming BitTorrent and M2M traffic have the anti-persistent features on the home network. It should be counted at the home network planning. The traffic control methods can be used on the home networks, for example traffic scheduling.

BitTorrent splits the files that are shared on a P2P network into fragments and then spreads these by giving the highest priority to the rarest fragment. We propose a mathematical model that takes into account several factors such as the peer distance, communication delays, and file fragment availability in a future period also by using a neural network module designed to model the behaviour of the peers. The ensemble comprising the proposed mathematical model and a neural network provides a solution for choosing the file fragments that have to be spread first, in order to ensure their continuous availability, taking into account that some peers will disconnect.

arXiv:1711.08060v1, The biggest overhead for the instantiation of a virtual machine in a cloud infrastructure is the time spent in transferring the image of the virtual machine into the physical node that executes it. This overhead becomes larger for requests composed of several virtual machines to be started concurrently, and the illusion of flexibility and elasticity usually associated with the cloud computing model may vanish. This poses a problem for both the resource providers and the software developers, since tackling those overheads is not a trivial issue. In this work we implement and evaluate several improvements for virtual machine image distribution problem in a cloud infrastructure and propose a method based on BitTorrent and local caching of the virtual machine images that reduces the transfer time when large requests are made., The authors acknowledge the financial support from the European Commission (via EGI-InSPIRE Grant Contract number RI-261323).

Persistent Identifiers (PID) are the foundation referencing digital assets in scientific publications, books, and digital repositories. In its realization, PIDs contain metadata and resolving targets in form of URLs that point to data sets located on the network. In contrast to PIDs, the target URLs are typically changing over time; thus, PIDs need continuous maintenance -- an effort that is increasing tremendously with the advancement of e-Science and the advent of the Internet-of-Things (IoT). Nowadays, billions of sensors and data sets are subject of PID assignment. This paper presents a new approach of embedding location independent targets into PIDs that allows the creation of maintenance-free PIDs using content-centric network technology and overlay networks. For proving the validity of the presented approach, the Handle PID System is used in conjunction with Magnet Link access information encoding, state-of-the-art decentralized data distribution with BitTorrent, and Named Data Networking (NDN) as location-independent data access technology for networks. Contrasting existing approaches, no green-field implementation of PID or major modifications of the Handle System is required to enable location-independent data dissemination with maintenance-free PIDs., Published IEEE paper of the FedCSIS 2016 (SoFAST-WS'16) conference, 11.-14. September 2016, Gdansk, Poland. Also available online: http://ieeexplore.ieee.org/document/7733372/