Abstract — Since the outbreak of peer-to-peer (P2P) networking with Napster during the late ’90s, P2P applications have multiplied, become sophisticated and emerged as a significant fraction of Internet traffic. At first, P2P traffic was easily recognizable since P2P protocols used specific application TCP or UDP port numbers. However, current P2P applications have the ability to use arbitrary ports to “camouflage” their existence. Thus only a portion of P2P traffic is clearly identifiable. As a result, estimates and statistics regarding P2P traffic are unreliable. In this paper we present a characterization of P2P traffic in the Internet. We develop several heuristics that allow us to recognize P2P traffic at nonstandard ports. We find that depending on the protocol and metric used, approximately 30%-70 % of traffic related to P2P applications cannot be identified using wellknown ports. In addition we present several characteristics for various P2P networks, such as eDonkey2000, Fasttrack,

Abstract — P2P file-sharing applications are quickly being adopted by a wider and more mainstream audience. There is much to be learned from keyword searches users perform in order to retrieve content from these networks. This paper presents a large-scale measurement study of search terms in the modern Gnutella network. We developed a highly parallelized architecture capable of capturing an unprecedented amount of geographical-identified queries. We applied this architecture to generate daily logs of search queries. We collected over 25 such daily Gnutella logs, with more than 15 millions unique queries in each, over a three month period. We analyzed both static snapshots of the Gnutella networks, as well as the dynamics of the network over time. In particular, we look at the geographic location and the trends of searches to better understand the dynamics. I.

We implement this attack both in simulation and in awide-area network, and show it severity both in terms of number of packets and total traffic generated. We engi-neer and implement a novel solution that does not require client or network modifications allowing for practical de-ployment. Additionally, we demonstrate the solution's efficiency on a real network. 1 Introduction Savage et al. [29] present three techniques by which amisbehaving TCP receiver can manipulate the sender into providing better service at the cost of fairness to othernodes. With one such technique, optimistic acknowledgment ("opt-ack"), the receiver deceives the sender by send-ing acknowledgments (ACKs) for data segments before they have actually been received. In effect, the connec-tion's round trip time is reduced and the total throughput increased. Savage et al. observe that a misbehav-ing receiver could use opt-ack to conceal data losses, thus improving end-to-end performance at the cost of data in-tegrity. They further suggest that opt-ack could potentially be used for denial of service, but do not investigate thisfurther. In this paper, we consider a receiver whose sole interestis exploiting opt-ack to mount a distributed denial of service (DoS) attack against not just individual machines, butentire networks. In this paper, we:

Peer-to-peer (P2P) file-sharing applications generate a large part if not most of today's Internet traffic. The large volume of this traffic (thus the high potential benefits of caching) and the large cache sizes required (thus nontrivial costs associated with caching) only underline that efficient cache replacement policies are important in this case. P2P file-sharing traffic has several characteristics that distinguish it from well studied Web traffic and that require a focused study of efficient cache management policies. This paper uses trace driven simulations to compare traditional cache replacement policies with new policies that try to exploit characteristics of the P2P file-sharing traffic generated by applications using FastTrack protocol.

Peer-to-peer (P2P) based networks have several desirable features for content distribution, such as low costs, scalability, and fault tolerance.

P2P systems that rely on the voluntary contribution of bandwidth by the individual peers may suffer from freeriding. To address this problem, mechanisms enforcing fairness in bandwidth sharing have been designed, usually by limiting the download bandwidth to the available upload bandwidth. As in real environments the latter is much smaller than the former, these mechanisms severely affect the download performance of most peers. In this paper we propose a system called 2Fast, which solves this problem while preserving the fairness of bandwidth sharing. In 2Fast, we form groups of peers that collaborate in downloading a file on behalf of a single group member, which can thus use its full download bandwidth. A peer in our system can use its currently idle bandwidth to help other peers in their ongoing downloads, and get in return help during its own downloads. We assess the performance of 2Fast analytically and experimentally, the latter in both real and simulated environments. We find that in realistic bandwidth limit settings, 2Fast improves the download speed by up to a factor of 3.5 in comparison to state-of-the-art P2P download protocols. 1.

Abstract — The concept of superpeer has been introduced to improve the performance of popular P2P applications. A superpeer is a “powerful ” node that acts as a server for a set of clients, and as an equal with respect to other superpeers. By exploiting heterogeneity, the superpeer paradigm can lead to improved efficiency, without compromising the decentralized nature of P2P networks. The main issues in constructing superpeer-based overlays are the selection of superpeers and the association between superpeers and clients. Generally, superpeers are either run voluntarily (without an explicit selection process), or chosen among the “best ” nodes in the network, for example those with the most abundant resources, such as bandwidth or storage. In several contexts, however, shared resources are not the only factor; latency between clients and superpeers may play an important role, for example in online games and IP-Telephony applications. This paper presents SG-2, a novel protocol for building and maintaining proximity-aware superpeer topologies. SG-2 uses a gossip-based protocol to spread messages to nearby nodes and a biology-inspired task allocation mechanism to promote the “best ” nodes to superpeer status. The paper includes extensive simulation experiments to prove the efficiency, scalability and robustness of SG-2. Index Terms — P2P, superpeer, overlay, latency, quality of service.

We investigate the circumstances under which it is possible to discourage free-riding in a peer-to-peer system for resource-sharing by prioritizing resource allocation to peers with higher reputation. We use a model to predict conditions necessary for any reputation scheme to succeed in discouraging free-riding by this method. We show with simulations that for representative cases, a very simple autonomous reputation scheme works nearly as well at discouraging free-riding as an ideal reputation scheme. Finally, we investigate the expected dynamic behavior of the system. 1

Abstract. Peer-to-peer environments exhibit a very high diversity in individual peer characteristics ranging by orders of magnitude in terms of uptime, available bandwidth, and storage space. Many systems attempt to exploit this resource heterogeneity by using the best performing and most reliable peers, called super-peers, for hosting system services. However, due to inherent decentralisation, scale, dynamism, and complexity of P2P environments, self-managing super-peer selection is a challenging problem. In this paper, decentralised aggregation techniques are used to reduce the uncertainty about system properties by approximating the peer utility distribution allowing peers to calculate adaptive thresholds in order to discover appropriate super-peers. Furthermore, a heuristic search algorithm is described that allows super-peers, above a certain utility threshold, to be eOEciently discovered and utilised by any peer in the system.1

Opportunistic sharing of Internet-connected resources is a low cost method for obtaining access to unprecedented-scale collections of resources. An essential service in any resource-sharing environment is resource discovery: given a description of the resources desired, a resource discovery mechanism returns locations of resources that match the description.