Giang T. Nguyen

Resilient and underlay-aware P2P live-streaming

Application Layer Multicast (ALM) represents a cost-efficient way to disseminate content in large scale. However, as it relies on end-systems in content distribution, it can be easily attacked and thus requires specific measures to increase its resilience against attacks. Besides attacks on end-users, few attention has been paid to attacks on the underlying transport network so far. When the overlay is not constructed in an underlay-aware manner, several overlay links may rely on the same link or router in the underlay. Hence, a single underlay failure may result in multiple, simultaneous overlay failures. Moreover, without considering the underlying transport network an inefficient content distribution can be the result. For this reason the ALM induced traffic load in transport networks can become rather large. In this article, we propose a construction algorithm for ALM topologies that incorporates information about the underlying network to improve their resilience against underlay failures, to maintain resilience against overlay attacks, and to increase the efficiency of the content distribution. Our simulation results indicate that the underlay dependence of the established ALM overlays can be nearly halved compared to overlays that do not use information about the transport network in their construction. As a result, the ALM induced traffic load in transport networks decreases considerably. In addition, the results indicate that our topologies are likewise resilient to underlay as well as overlay attacks.

On the Resilience of Pull-Based P2P Streaming Systems against DoS Attacks

The robustness of pull-based streaming systems to node failure and churn has been extensively analyzed. Their resistance to sabotage, however, is not well understood, so far. Recent measurement studies on a large deployed pull-based system have discovered stable source-to-peer paths and the convergence of the content dissemination to rather static topologies over time. Thus, an attack on central nodes within these static topologies, which causes serious service disruptions, is feasible. This paper demonstrates attacks that significantly reduce the system’s performance. As a countermeasure, we introduce a novel striping scheme, which decreases the dependencies between peers and thus the impact of attacks. A thorough simulation study indicates that our scheme achieves a high resistance against sabotage attacks at negligible overhead and performance penalties.

RBCS: A resilient backbone construction scheme for hybrid Peer-To-Peer streaming

Hybrid Peer-to-Peer streaming systems combine the advantages of an efficient push-based with a more resilient pull-based system to deliver video streams over the Internet. In this manner, hybrid systems offer low latency and an increased robustness to failures and node churn. However, current hybrid systems is vulnerable to misbehaving nodes and deliberate attacks. By taking central positions in the overlay, malicious nodes can perform extremely harmful Denial-of-Service (DoS) attacks. We propose RBCS, a novel backbone construction scheme, that is highly resilient against DoS attacks while maintaining fast content dissemination. RBCS incorporates stable peers into a manipulation-resistant multi-tree backbone overlay, which is resilient against both attacks and node churn. Additionally, RBCS securely identifies stable peers by using only local knowledge about the participation time of others. Extensive simulations indicate that RBCS outperforms the state-of-the-art in being more resilient against attacks at the price of a slightly increased overhead.

Integrating churn into the formal analysis of routing algorithms

Mathematical modeling and analysis of distributed systems, mostly applied with the goal of the correctness or asymptotic behavior of a system, rarely provides concrete results and often disregards or simplifies network dynamics. However, concrete performance bounds on a system under churn are highly useful both as a validation of empirical results and a scalable alternative to simulations. In this paper, we first present an abstract methodology for deriving the success probability of an action, such as routing, in a dynamic system, using the session length distribution as the decisive parameter. We evaluate the developed methodology by giving concrete bounds on the success probability of recursive routing. The results do not only show the adaptability of our model, but also reveal that a considerable fraction of routing attempts fails due to a leaving node on the return path rather than due to not reaching the target.

SWAP: Protecting pull-based P2P video streaming systems from inference attacks

In pull-based Peer-to-Peer video streaming systems, peers exchange buffer maps to reveal the availability of video chunks in their buffer. When collecting these buffer maps, a malicious party can infer the systems overlay structure and even identify head nodes, the direct communication partners of the streams source. Attacking these head nodes can isolate peers from the source resulting in a disruption of the video dissemination for most peers in the system. We introduce a lightweight SWAP scheme, which allows peers to proactively change their partners, to reduce the chance of head nodes to be identified by such an inference attacker. Extensive simulation studies demonstrate that our scheme effectively undermines the attacks accuracy in identifying head nodes. So, SWAP lowers the chunk miss ratio while causing only a slight increase in signaling overhead.

Resilient tree-based live streaming for mobile scenarios

Using Peer-to-Peer technology to deliver live video streams to mobile devices is a promising approach. It allows service providers to scale their video distribution without increasing their cost. As the resources are replicated at the edge of the network, mobile devices can take advantage of close-by peers in order to get the required data faster. This, however, is challenging due to the highly dynamic nature of the participating mobile devices. Hence, the video distribution overlay needs to adapt quickly to changes in the available bandwidth as well as the location of peers. Also, it should be resilient to arbitrary disconnects as well as targeted attacks. In this paper, we introduce a multi-tree-push streaming system which takes the upload capacities of mobile devices into account and arranges the overlay connections based on their position in the network topology. Our demonstrations show that our system is resilient to churn and attacks while running on desktop machines and mobile devices.

Resilient tree-based live streaming in reality

Our main contribution in this work is a deployable multitree-push system for P2P-based live streaming. It runs on both desktop PCs and Android-based mobile devices. Additionally, it provides controlling, monitoring, and measurement functionalities which help with debugging in the development phase, visualize the topology during a demonstration, and support the deployment of test scenarios in a distributed setting. Besides, the generic architecture of the system also allows for the extension to other classes of streaming systems.

Potential of Municipal Solid Waste in Hanoi for Energy Utilisation

The integration of Renewable Energy Sources (RES) within the contextual framework of existing thermal energy production systems has emerged as a promising and sustainable policy towards addressing the growing global energy demand. Especially for developing countries, as they are characterized by decentralized energy systems, locally available RES are a viable option for generating thermal energy. In this chapter, we provide a methodological framework for integrating waste biomass into a portfolio of supply chains for thermal energy production, by presenting the relevant drivers for waste biomass usage making especially the case for developing countries, the associated systems and the supply chain operations. A generic strategic optimization model is proposed for determining the optimal mixture of energy sources for a specific region. This model could be employed by a system’s regulator to conduct various ‘what-if’ analyses, in order to develop comprehensive effective policies that also integrate waste biomass into the existing energy system. Finally, a real-world case study is presented, and interesting managerial insights are discussed.