Locality-aware P2P Research Articles

Optimality analysis of locality-aware tit-for-tat-based P2P file distribution

In the current Internet, periodic software update is essential to maintain systems secure from malicious attacks. In case of proliferated software, e.g., Operating System (OS), the distribution server for update tends to be a bottleneck, due to the concentration of users’ requests. To tackle this problem, several systems, e.g., Windows Update, have been applying the Peer-to-Peer (P2P) file distribution technique where clients called peers upload retrieved fragments of the original file, i.e., pieces, to others. However, peers may not be willing to upload pieces to others, due to their own communication overhead. BitTorrent has adopted the Tit-for-Tat (TFT) strategy in game theory, which encourages peers to exchange an equivalent number of pieces among each pair of peers. In recent years, the optimality of TFT-based P2P content distribution, i.e., file distribution and streaming, has been analyzed with the help of Integer Linear Programming (ILP). In this paper, considering the fact that the communication overhead inside a group, e.g., LAN or Autonomous System (AS), is much less than that of between groups, we model locality-aware TFT-based P2P file distribution where the TFT constraint is relaxed for intra-group communications. We further formulate the optimal piece flow determination problem as ILP in the similar way to the existing work. Through numerical results, we show that the locality-aware TFT-based P2P file distribution can achieve quasi-optimal average file download time when the upload capacity of the server is a bottleneck and the number of groups is moderate.

A Distance-driven alliance for a P2P live video system

In peer-to-peer (P2P) networks, free-riders and redundant streams including overlapped and folded streams dramatically degrade playback quality and network performance, respectively. Although a locality-aware P2P live video can reduce the topological complexity, it cannot effectively avoid redundant streams while denying free-riders. In this paper, we first model free-rider, redundant streams and a distance-driven P2P system. Based on that model, a distance-driven alliance algorithm is proposed to construct not only an alliance that directly prevents any utility gains of free-riders through inter-user constraints but also a small-world network or a multicast tree that effectively reduces redundant streams. Finally, simulations confirm its advantages in functionality and performance over several existing strategies and distance-driven P2P live video systems.

PON versus AON: Which is the best solution to offload core network by peer-to-peer traffic localization

Video streaming and video-on-demand are gaining popularity nowadays which dictates a need of bandwidth upgrade for Internet users. Many next generation optical access network architectures have been proposed to meet high capacity requirement on a per-user basis. However, the capacity upgrade in access networks, may lead to a huge traffic growth in the aggregation/core network. One way to avoid this problem is to keep the traffic locally (i.e., inside the access network area) as much as possible. It can be obtained by using locality-aware peer-to-peer (P2P) applications for content distribution and has the potential to offload the core segment. However, various optical access network architectures accommodate the P2P traffic in different ways. Thus, it is important to study these differences in order to identify the best architecture option for capacity offloading in the core network, energy efficiency and network resource utilization. By deploying a proper architecture in the access segment along with an efficient traffic locality aware strategy, the extra investment and capacity upgrade of the expensive core network resources needed to support the future traffic expansion can be minimized. However, to the best of our knowledge this kind of assessment is so far not available.Therefore, in this paper, we analyze the efficiency of supporting locality-aware P2P video distribution algorithm in three main types of optical access network architectures, i.e., active optical network (AON), wavelength division multiplexing passive optical network (WDM PON) and time/wavelength division multiplexing PON (TWDM PON). Our goal is to provide important design guidelines for the next generation broadband access architectures, while minimizing the need for the core network upgrade. We obtain this objective by utilizing the unique characteristics of each access network architecture in accommodating P2P video delivery applications. We have done an extensive literature study and for the first time we have compared performance of these architectures with respect to the amount of the traffic on the links in different aggregation levels, power consumption taking into account sleep mode functionality at the user premises, and required switching capacity in the nodes. Our results reveal that both active and passive architectures have good ability to localize P2P traffic, whereas they show distinct performance with respect to the other aforementioned aspects. This is caused by the different number of aggregation levels, link capacity, and resource allocation protocols. Considering the overall performance evaluation, it is shown that TWDM PON is the most promising option for the future broadband access, where locality-aware P2P video distribution is applied, thanks to its low energy consumption and required switching capacity of the network equipment needed to deliver this service. This conclusion is against the general intuition because of the PON׳s centralized control plane and passive infrastructure without switching capability in the field. Our unexpected conclusion can be of particular interest to operators as it is perfectly aligned with next generation optical access architecture identified by Full Service Access Networks (FSAN).

Characterizing Locality-aware P2P Streaming

Peer-to-peer (P2P) live streaming systems have been increasingly popular and successful in today's Internet, which provide large collections of video channels to millions of users at low server costs. The large volumes of P2P streaming traffic are exceeding those incurred by BitTorrent-like file sharing applications, threatening huge traffic relay cost to the Internet service providers (ISPs). There have recently emerged proposals advocating locality-aware P2P streaming protocol design, which aim to constrain streaming traffic within ISP boundaries and to alleviate traffic relay cost to the Internet Service Providers (ISPs). Nevertheless, there is a lack of in-depth understanding on the impact of such a locality-aware design on P2P streaming performance. Taking an analytical approach, we model the relation between streaming performance and traffic locality in P2P live streaming systems, in order to acquire useful insights for designing high-performance locality-aware real-world systems. We use end-to-end streaming delays as the performance metric for live streaming, and the number of copies of the live streams imported into an ISP to evaluate the volume of inter-ISP traffic. Considering multiple ISPs at different bandwidth levels, we characterize the generic relationship between the volume of inter-ISP traffic and the streaming performance; we then analyze the traffic volume when the best streaming performance is achieved and the streaming performance when minimum inter-ISP traffic is incurred. Our models and analyses provide intriguing insights on the design of effective locality-aware peer selection protocols and server deployment strategies across multiple ISPs. We also evaluate our models and theoretical results with large-scale simulations under realistic settings.

Topology control strategies on P2P live video streaming service with peer churning

The research community and Internet Service Providers (ISPs) are interested in designing locality-aware P2P applications, which balance the trade-off between localizing traffic and satisfying the quality of service requirements of the application. To this aim, taking into account the architecture considered by the Application Layer Traffic Optimization (ALTO) IETF Working Group, the paper proposes a study on the control of the P2P topology in a single operator intra-domain scenario, based on the K-Minimum Spanning Tree (K-MST) algorithm. In particular, the paper contribution can be summarized as follows: (i) the definition of a lower and an upper bound of the locality parameter of a P2P topology, (ii) the proposal of a heuristic, denoted as K-Better-Neighbors (KBN), for controlling the P2P topology in presence of peer churning, (iii) the discussion of different solutions based on periodic topology optimization to manage the P2P system in presence of peer churning, and (iv) the comparison of the system performance obtained by the proposed solutions and some reference strategies in a dynamic scenario, from both the ISP and user perspective.

Adaptive Search Radius – Using hop count to reduce P2P traffic

Peer-to-Peer (P2P) file sharing accounts for a very significant part of the Internet’s traffic, affecting the performance of other applications and translating into significant peering costs for ISPs. It has been noticed that, just like WWW traffic, P2P file sharing traffic shows locality properties, which are not exploited by current P2P file sharing protocols. We propose a peer selection algorithm, Adaptive Search Radius (ASR), where peers exploit locality by only downloading from those other peers which are nearest (in network hops). ASR ensures swarm robustness by dynamically adapting the distance according to file part availability. ASR aims at reducing the Internet’s P2P file sharing traffic, while decreasing the download times perceived by users, providing them with an incentive to adopt this algorithm. We believe ASR to be the first locality-aware P2P file sharing system that does not require assistance from ISPs or third parties nor modification to the server infrastructure. We support our proposal with extensive simulation studies, using the eDonkey/eMule protocol on SSFNet. These show a 19 to 29% decrease in download time and a 27 to 70% reduction in the traffic carried by tier-1 ISPs. ASR is also compared (favourably) with Biased Neighbour Selection (BNS), and traffic shaping. We conclude that ASR and BNS are complementary solutions which provide the highest performance when combined. We evaluated the impact of P2P file sharing traffic on HTTP traffic, showing the benefits on HTTP performance of reducing P2P traffic. A plan for introducing ASR into eMule clients is also discussed. This will allow a progressive migration to ASR enabled versions of eMule client software. ASR was also successfully used to download from live Internet swarms, providing significant traffic savings while finishing downloads faster.

Foreword of Special Issue on “Nomadic Services and Applications”

Foreword of Special Issue on “Nomadic Services and Applications”

Locality-Awareness in BitTorrent-Like P2P Applications

This paper presents the measurement study of locality-aware P2P solutions over real-world Internet autonomous systems (AS) topology. By using the accesses of nodes of PlanetLab testbed, we create a detailed AS-level map including the end-to-end path of all nodes, as well as the relationship of all involved ASes. Based on this map, we evaluate the performance of a set of locality-aware P2P solutions, including an optimal solution guaranteeing the minimum AS hop count, as well as modified BitTorrent system with locality-awareness built into its neighbor selection, peer choking/unchoking, and piece selection processes. Our findings suggest that locality-awareness can help existing P2P solution to significantly decrease load on Internet, and achieve shorter downloading time. By comparing the performance of different kinds of locality-aware and traditional BitTorrent systems, we also point out the necessity to tradeoff between the goals of optimizing AS-related performance and achieving fairness among peers such as intra-AS traffic and peer burden fairness.

An Efficient Semantic-Based Search Schema in Unstructured P2P Network

How to efficiently organize and manage distributed resources is a critical issue of P2P systems. In this paper, we focus on both the P2P search mechanism and the topology structure of overlay network which are the key factors to dominate the performance of resource search and discovery. We mostly concern these issues as follows: Heterogeneity of nodes in P2P networks. Topology match between the P2P overlay network and the underlying physical network. In general, most peers that hold similar shared resources have similar requirements. We consider all the factors mentioned above, and propose a semantic-based and locality-aware hybrid P2P architecture (SLHP) including the method of model construction and maintenance and the multi-root mechanism to avoid the single point failure. SLHP considers the physical locality and the semantic similarity of the shared resource at the same time, in which nodes are clustered into domains according to the physical distance, and the nodes in a domain are clustered into groups according to the similar shared resource. The physical distance is measured by the RTT value of two peers. The calculation method of semantic similarity is also given. And then a semantic-based search schema is proposed. When the search occurs, the query is forwarded to super peers, and among super peers the query is forwarded to the neighbors who have the most similar shared resource with the query keyword. We also give a proof that according to the algorithm of construction and maintenance of SLHP, it is ensured that the existed resource must be found in theory. The semantic-based search can reduce the number of the transferred messages comparing with the standard flooding scheme, since it only produces k messages each hop, and forward to the most expected peers. Along with the routing indices being optimized continuously, which represents the knowledge of nodes about the entire overlay network, the hit ratio can be improved. Finally, in order to evaluate the performance of semantic-based search schema, three sets of simulations are set up to evaluate the key features of the network topology and semantic-based search algorithm. Experimental results show that the semantic-based search schema can reduce the search space, and get a good tradeoff between the performance and the overhead.

Nearcast

Peer-to-peer (P2P) live video streaming has been widely used in distance education applications to deliver the captured video courses to a large number of online students. By allowing peers serving each other in the network, P2P technology overcomes many limitations in the traditional client-server paradigm to achieve user and bandwidth scalabilities. However, existing systems do not perform well when the number of online students increases, and the system performance degrades seriously. One of the reasons is that the construction of the peer overlay in existing P2P systems has not considered the underlying physical network topology and can cause serious topology mismatch between the P2P overlay network and the physical network. The topology mismatch problem brings great link stress (unnecessary traffic) in the Internet infrastructure and greatly degrades the system performance. In this article, we address this problem and propose a locality-aware P2P overlay construction method, called Nearcast , which builds an efficient overlay multicast tree by letting each peer node choose physically closer nodes as its logical children. We have conducted extensive simulations to evaluate the performance of Nearcast in comparison with the existing RTT and NICE protocols. Also, Nearcast has been deployed on a wide-area network testbed to delivery video coursed to about 7200 users distributed across 100 collages in 32 cities in China. The experimental results show that Nearcast leads to lower link stress and shorter end-to-end latencies compared with the RTT and NICE protocols.

Locality-aware P2P query search with ISP collaboration

More than half of Internet traffic today is contributed by peer-to-peer (P2P) systems. Yet P2P systems build their overlay topology largely agnostic of the Internet underlay, which often leads to traffic management challenges for Internet Service Providers (ISP) and potentially inefficient neighbourhood selection for P2P nodes. To overcome this, we propose to use an oracle hosted by the ISPs, so that ISPs and P2P users can cooperate for improved performance. The oracle can be queried by P2P nodes while choos- ing neighbours for content search, and it will rank the possible neighbours of the querying node according to a locality indication, like location within the same AS, or the AS-hop distance. The ISP gains by keeping traffic within its Autonomous System (AS), and the P2P node can experience improved performance like lesser delay and better bandwidth. <br> In this paper, we evaluate the benefits of our scheme by performing experiments in a real Testlab as well as a simulation framework. We show how we configure representative AS topologies for P2P networks, and present experimental results with content search phase of a P2P network using different file sharing and search query distributions.

Exploiting Geographical and Temporal Locality to Boost Search Efficiency in Peer-to-Peer Systems

As a hot research topic, many search algorithms have been presented and studied for unstructured peer-to-peer (P2P) systems during the past few years. Unfortunately, current approaches either cannot yield good lookup performance, or incur high search cost and system maintenance overhead. The poor search efficiency of these approaches may seriously limit the scalability of current unstructured P2P systems. In this paper, we propose to exploit two-dimensional locality to improve P2P system search efficiency. We present a locality-aware P2P system architecture called Foreseer, which explicitly exploits geographical locality and temporal locality by constructing a neighbor overlay and a friend overlay, respectively. Each peer in Foreseer maintains a small number of neighbors and friends along with their content filters used as distributed indices. By combining the advantages of distributed indices and the utilization of two-dimensional locality, our scheme significantly boosts P2P search efficiency while introducing only modest overhead. In addition, several alternative forwarding policies of Foreseer search algorithm are studied in depth on how to fully exploit the two-dimensional locality