Incentive-driven QoS in peer-to-peer overlays

A well known problem in peer-to-peer overlays is that no single entity has control over the software, hardware and configuration of peers. Thus, each peer can selfishly adapt its behaviour to maximise its benefit from the overlay. This thesis is concerned with the modelling and design of incentive mechanisms for QoS-overlays: resource allocation protocols that provide strategic peers with participation incentives, while at the same time optimising the performance of the peer-to-peer distribution overlay. The contributions of this thesis are as follows. First, we present PledgeRoute, a novel contribution accounting system that can be used, along with a set of reciprocity policies, as an incentive mechanism to encourage peers to contribute resources even when users are not actively consuming overlay services. This mechanism uses a decentralised credit network, is resilient to sybil attacks, and allows peers to achieve time and space deferred contribution reciprocity. Then, we present a novel, QoS-aware resource allocation model based on Vickrey auctions that uses PledgeRoute as a substrate. It acts as an incentive mechanism by providing efficient overlay construction, while at the same time allocating increasing service quality to those peers that contribute more to the network. The model is then applied to lagsensitive chunk swarming, and some of its properties are explored for different peer delay distributions. When considering QoS overlays deployed over the best-effort Internet, the quality received by a client cannot be adjudicated completely to either its serving peer or the intervening network between them. By drawing parallels between this situation and well-known hidden action situations in microeconomics, we propose a novel scheme to ensure adherence to advertised QoS levels. We then apply it to delay-sensitive chunk distribution overlays and present the optimal contract payments required, along with a method for QoS contract enforcement through reciprocative strategies. We also present a probabilistic model for application-layer delay as a function of the prevailing network conditions. Finally, we address the incentives of managed overlays, and the prediction of their behaviour. We propose two novel models of multihoming managed overlay incentives in which overlays can freely allocate their traffic flows between different ISPs. One is obtained by optimising an overlay utility function with desired properties, while the other is designed for data-driven least-squares fitting of the cross elasticity of demand. This last model is then used to solve for ISP profit maximisation

Sustainable Cooperation in Peer-To-Peer Networks

Traditionally, peer-to-peer systems have relied on altruism and reciprocity. Although incentive-based models have gained prominence in new-generation peer-to-peer systems, it is essential to recognize the continued importance of cooperative principles in achieving performance, fairness, and correctness. The lack of this acknowledgment has paved the way for selfish peers to gain unfair advantages in these systems. As such, we address the challenge of selfish peers by devising a mechanism to reward sustained cooperation. Instead of relying on global accountability mechanisms, we propose a protocol that naturally aggregates local evaluations of cooperation. Traditional mechanisms are often vulnerable to Sybil and misreporting attacks. However, our approach overcomes these issues by limiting the benefits selfish peers can gain without incurring any cost. The viability of our algorithm is proven with a deployment to 27,259 Internet users and a realistic simulation of a blockchain gossip protocol. We show that our protocol sustains cooperation even in the presence of a majority of selfish peers while incurring only negligible overhead

SMART: A Subspace based Malicious Peers Detection algorithm for P2P Systems

In recent years, reputation management schemes have been proposed as promising solutions to alleviate the blindness during peer selection in distributed P2P environment where malicious peers coexist with honest ones. They indeed provide incentives for peers to contribute more resources to the system and thus promote the whole system performance. But few of them have been implemented practically since they still suffer from various security threats, such as collusion, Sybil attack and so on. Therefore, how to detect malicious peers plays a critical role in the successful work of these mechanisms, and it will also be our focus in this paper. Firstly, we define malicious peers and show their influence on the system performance. Secondly, based on Multiscale Principal Component Analysis (MSPCA) and control chart, a Subspace based MAlicious peeRs deTecting algorithm (SMART) is brought forward. SMART first reconstructs the original reputation matrix based on subspace method, and then finds malicious peers out based on Shewhart control chart. Finally, simulation results indicate that SMART can detect malicious peers efficiently and accurately

LiveShift: mesh-pull P2P live and time-shifted video streaming

The popularity of video sharing over the Internet has increased significantly. High traffic generated by such applications at the source can be better distributed using a peer-to-peer overlay. LiveShift combines both live and on-demand video streaming -- while video is transmitted through the peer-to-peer network in a live fashion, all peers participate in distributed storage. This adds the ability to replay time-shifted streams from other peers in a distributed and scalable manner. This technical report describes an architecture, a mesh-pull protocol, and a set of policies that support the envisioned use case enable. User-focused evaluation results show its effectiveness and limits in terms of quality of experience

LiveShift: Mesh-pull live and time-shifted P2P video streaming

The popularity of video sharing over the Internet has increased significantly. High traffic generated by such applications at the source can be better distributed using a peer-to-peer (P2P) overlay. Unlike most P2P systems, LiveShift combines both live and on-demand video streaming while video is transmitted through the peer-to-peer network in a live fashion, all peers participate in distributed storage. This adds the ability to replay time-shifted streams from other peers in a distributed and scalable manner. This paper describes an adaptive fully-distributed mesh-pull protocol that supports the envisioned use case and a set of policies that enable efficient usage of resources, discussing interesting trade-offs encountered. User-focused evaluation results, including both channel switching and time shifting behavior, show that the proposed system provides good quality of experience for most users, in terms of infrequent stalling, low playback lag, and a small proportion of skipped blocks in all the scenarios studied, even in presence of churn

Conciliando satisfação e paridade para promover reciprocidade em federações de provedores de computação na nuvem.

Provedores privados de computação na nuvem poderiam obter considerável benefício mútuo ao operar suas infraestruturas de forma federada. Tal operação permite que a demanda excedente de um provedor possa ser atendida por outros provedores que estejam experimentando uma baixa demanda naquele mesmo instante. Sob uma ótica de mercado, federações com arquitetura descentralizada têm como principal desafio a promoção de cooperação entre indivíduos egoístas e racionais em um cenário que não dispõe de uma autoridade central e confiável. Este trabalho se concentra em arquiteturas de mercado descentralizado, baseadas em mecanismos de reciprocidade, para suporte a federações P2P (Peer-to-Peer) de provedores de computação na nuvem. Nos mecanismos de reciprocidade, um indivíduo utiliza o histórico de comportamentos de cooperação dos demais indivíduos para doar seus recursos aos que forem mais recíprocos. A maioria dessas estratégias se atém à priorização dos participantes (a quem devo doar?) de acordo com métricas tais como reputação ou grau de reciprocidade. Essa estratégia é suficiente para promover cooperação e assegurar aos participantes cooperativos os melhores níveis possíveis de satisfação (percentual de requisições atendidas). Porém, em cenários com baixa contenção de recursos, a priorização por si só não é suficiente para evitar o aproveitamento por parte de indivíduos não-cooperativos e garantir paridade (percentual de recursos retribuídos). Neste sentido, este trabalho propõe que mecanismos de reciprocidade, especialmente aqueles baseados em reciprocidade direta, sejam estendidos com um laço de controle retroalimentado que regula a quantidade de recursos que cada nuvem deveria ofertar à federação. Quando cada participante cooperativo controla de maneira individual a quantidade de recursos ofertada à federação, tem-se como resultado um controle indireto da contenção de recursos, que por sua vez é mantida em um patamar que assegura aos participantes cooperativos níveis adequados de satisfação e paridade. Por fim, é apresentada uma investigação acerca da utilização de uma forma mais limitada de reciprocidade indireta, a reciprocidade transitiva, que pode ser utilizada conjuntamente com mecanismos de reciprocidade direta, para evitar impasses gerados pela assimetria de tempo/interesses, aquecendo a economia da federação e consequentemente provendo maiores níveis de paridade e satisfação aos nós cooperativos.Private cloud providers could obtain considerable benefits from operating their infrastructures within a federation. Such operation allows a provider’s exceeding demand to be met by other providers experimenting a resource underutilization on the same moment. From a market perspective, federations with decentralized architecture have as main challenge the promotion of cooperation among rational selfish individuals in a context with no central trusted authorities. This work focuses in decentralized market architectures, based on reciprocity mechanisms, to support P2P (Peer-to-Peer) federations of cloud providers. In reciprocity mechanisms, an individual uses the history of behaviors of other individuals, reflecting their cooperation levels, in order to prioritize the provision of resource to those shown to be the most reciprocative. Most of these strategies are restricted to the prioritization of participants (to whom should I donate?) according to metrics such as reputation or degree of reciprocity. This strategy is sufficient to promote cooperation and assure cooperative participants the best possible levels of satisfaction (percentage of requests met). However, in low resource contention scenarios, prioritization alone is not sufficient to avoid resource provision to non-cooperative individuals and thus to guarantee fairness (percentage of resources reciprocated). In this sense, this work proposes that mechanisms of reciprocity, especially those based on direct reciprocity, be extended with a feedback control loop that regulates the amount of resources that each cloud should offer to the federation. When each cooperative participant controls individually the amount of resources offered to the federation, there is an indirect control of resource contention, which in turn is kept at a level that ensures cooperative participants adequate levels of satisfaction and fairness. Finally, an investigation on the use of a more limited form of indirect reciprocity is presented, the transitive reciprocity, which can be used in conjunction with direct reciprocity mechanisms to avoid deadlocks generated by time/interest asymmetry, moving the federation’s economy and consequently assuring higher levels of fairness and satisfaction to cooperative nodes.Cape