Eng Keong Lua

A survey and comparison of peer-to-peer overlay network schemes

Over the Internet today, computing and communications environments are significantly more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. There has been much interest in emerging Peer-to-Peer (P2P) network overlays because they provide a good substrate for creating large-scale data sharing, content distribution, and application-level multicast applications. These P2P overlay networks attempt to provide a long list of features, such as: selection of nearby peers, redundant storage, efficient search/location of data items, data permanence or guarantees, hierarchical naming, trust and authentication, and anonymity. P2P networks potentially offer an efficient routing architecture that is self-organizing, massively scalable, and robust in the wide-area, combining fault tolerance, load balancing, and explicit notion of locality. In this article we present a survey and comparison of various Structured and Unstructured P2P overlay networks. We categorize the various schemes into these two groups in the design spectrum, and discuss the application-level network performance of each group.

Internet routing policies and round-trip-times

Round trip times (RTTs) play an important role in Internet measurements. In this paper, we explore some of the ways in which routing policies impact RTTs. In particular, we investigate how routing policies for both intra- and inter-domain routing can naturally give rise to violations of the triangle inequality with respect to RTTs. Triangle Inequality Violations (TIVs) might be exploited by overlay routing if an end-to-end forwarding path can be stitched together with paths routed at layer 3. However, TIVs pose a problem for Internet Coordinate Systems that attempt to associate Internet hosts with points in Euclidean space so that RTTs between hosts are accurately captured by distances between their associated points. Three points having RTTs that violate the triangle inequality cannot be embedded into Euclidean space without some level of inaccuracy. We argue that TIVs should not be treated as measurement artifacts, but rather as natural features of the Internets structure. In addition to explaining routing policies that give rise to TIVs, we present illustrating examples from the current Internet.

On the accuracy of embeddings for internet coordinate systems

Internet coordinate systems embed Round-Trip-Times (RTTs) between Internet nodes into some geometric space so that unmeasured RTTs can be estimated using distance computation in that space. If accurate, such techniques would allow us to predict Internet RTTs without extensive measurements. The published techniques appear to work very well when accuracy is measured using metrics such as absolute relative error. Our main observation is that absolute relative error tells us very little about the quality of an embedding as experienced by a user. We define several new accuracy metrics that attempt to quantify various aspects of user-oriented quality. Evaluation of current Internet coordinate systems using our new metrics indicates that their quality is not as high as that suggested by the use of absolute relative error.

Phoenix: A Weight-Based Network Coordinate System Using Matrix Factorization

Network coordinate (NC) systems provide a lightweight and scalable way for predicting the distances, i.e., round-trip latencies among Internet hosts. Most existing NC systems embed hosts into a low dimensional Euclidean space. Unfortunately, the persistent occurrence of Triangle Inequality Violation (TIV) on the Internet largely limits the distance prediction accuracy of those NC systems. Some alternative systems aim at handling the persistent TIV, however, they only achieve comparable prediction accuracy with Euclidean distance based NC systems. In this paper, we propose an NC system, so-called Phoenix, which is based on the matrix factorization model. Phoenix introduces a weight to each reference NC and trusts the NCs with higher weight values more than the others. The weight-based mechanism can substantially reduce the impact of the error propagation. Using the representative aggregate data sets and the newly measured dynamic data set collected from the Internet, our simulations show that Phoenix achieves significantly higher prediction accuracy than other NC systems. We also show that Phoenix quickly converges to steady state, performs well under host churn, handles the drift of the NCs successfully by using regularization, and is robust against measurement anomalies. Phoenix achieves a scalable yet accurate end-to-end distances monitoring. In addition, we study how well an NC system can characterize the TIV property on the Internet by introducing two new quantitative metrics, so-called RERPL and AERPL. We show that Phoenix is able to characterize TIV better than other existing NC systems.

Scalable multicasting with network-aware geometric overlay

Abstract It is crucial to design an efficient network-aware overlay network to enable multicast service to adjust under the dynamic underlying network conditions and node churn in a scalable manner without extensive network measurements. We propose an accurate and scalable Internet subspace geometry to embed the nodes onto a geometric plane by measuring delay latencies between some nodes and assign geometric coordinates to all nodes in such a way that the geometric distances between node coordinates closely approximate their delay latencies. We exploit this Internet subspace geometry to design a network-aware SuperPeers–Peers geometric overlay hierarchy. This is maintained locally in a distributed manner allowing lightweight self-organization. We then create shortest-path overlay multicast tree based on shortest geometric distances between SuperPeers at the SuperPeers layer for overlay multicasting. This low-latency and high-bandwidth multicast backbone infrastructure will serve the Peers in the lower layer. We evaluate our proposals on the 10 massive scale networks each consisting of 100,000 nodes and in the PlanetLab. Our performance evaluation results show high efficiency and good scalability .

Phoenix: Towards an Accurate, Practical and Decentralized Network Coordinate System

Network coordinate (NC) system allows efficient Internet distance prediction with scalable measurements. Most of the NC systems are based on embedding hosts into a low dimensional Euclidean space. Unfortunately, the accuracy of predicted distances is largely hurt by the persistent occurrence of Triangle Inequality Violation (TIV) in measured Internet distances. IDES is a dot product based NC system which can tolerate the constraints of TIVs. However, it cannot guarantee the predicted distance non-negative and its prediction accuracy is close to the Euclidean distance based NC systems. In this paper, we propose Phoenix, an accurate, practical and decentralized NC system. It adopts a weighted model adjustment to achieve better prediction accuracy while it ensures the predicted distances to be positive and usable. Our extensive Internet trace based simulation shows that Phoenix can achieve higher prediction accuracy than other representative NC systems. Furthermore, Phoenix has fast convergence and robustness over measurement anomalies.

Securing Peer-to-Peer Content Sharing Service from Poisoning Attacks

Poisoning attacks in the Peer-to-Peer (P2P) content sharing service have become a serious security problem on the global Internet due to the features of P2P systems such as self-organization, self-maintenance, etc. In this paper, we propose a novel poisoning-resistant security framework based on the notion that the content providers would be the only trusted sources to verify the integrity of the requested content. To provide the mechanisms of availability and scalability, a content provider publishes the information of his shared contents to a group of content maintainers self-organized in a security overlay, so that a content requestor can verify the integrity of the requested content from the associated content maintainers. Two defense functions are first carried out - filtering out malicious activities and selecting the authentic content version. Then, the content requestor can perform the content integrity verification while downloading and take prompt protection actions to handle content poisoning attacks. To further enhance the system performance, we devise a scalable probabilistic verification scheme. The evaluation results illustrate that our framework can effectively and efficiently defend against content poisoning in various scenarios.

On the Quality of Triangle Inequality Violation Aware Routing Overlay Architecture

It is known that Internet routing policies for both intra- and inter-domain routing can naturally give rise to triangle inequality violations (TIVs) with respect to quality of service (QoS) network metrics such as latencies between nodes. This motivates the exploitation of such TIVs phenomenon in network metrics to design TlV-aware routing overlay architecture which is capable of choosing quality overlay routing paths to improve end-to-end QoS without changing the underlying network architecture. Our idea is to find quality overlay routes between node pairs based on TIV optimization in terms of the latency and packet loss ratio, and that can offer near optimal routing quality in cost-effective and scalable manner. Our intuition to do this is to choose these overlay routes from a small set of transit nodes. We propose to assign nodes with transit selection frequency scores that are computed based on previous node usage for transit, and consolidate a small set of highly ranked transit nodes. For every node pair, we choose the best transit node in this small set for overlay routing, based on TIV optimization in latency and packet loss ratio. We analyze the quality of our TlV-aware routing overlay algorithm analytically and using real Internet measurements on latency and packet loss ratio. Our results show good quality performance in improving end-to-end QoS routing.

Embeddable Overlay Networks

Internet round-trip-times (RTTs) exhibit widespread and persistent Triangle Inequality Violations (TIVs). It has been shown that TIVs are a natural consequence of the Internets routing structure and they degrade the embedding accuracy of any Internet coordinate systems based on RTTs. In this paper, we simulate a coordinate system in a hypothetical overlay environment where RTTs are measured with respect to overlay forwarding that has eliminated all the TIVs. The resulting coordinate system is much more accurate and the embedding accuracy is predictable and stable (under simulated node churn) than the existing techniques based on RTTs along paths chosen by native IP forwarding. We believe that this work helps to illustrate the detrimental effects of TIVs on Internet coordinate systems, and it suggests that high quality coordinate systems in the global Internet may be possible only with overlay forwarding.

Security for emerging ubiquitous networks

Emerging ubiquitous networks will enable interac- tions between various types of device, in both wired and wireless networks, and among Peer-to-Peer (P2P) overlay networks. Dy- namic, heterogeneous and distributed P2P overlay networks will help to create new ubiquitous services, through the convergence of communication technologies and highly adaptive reconfigurable devices. In this paper, we will give an overview of the evolution of ubiquitous networks, its security architectures and challenges. We describe our proposal of a practical security protocol model for ubiquitous networks which is computationally fast and requires low memory resources. Our technique combines both network authentication technique based on symmetric keys and single sign-on mechanisms. In our security protocol model, there are three stages of securing user and application access in ubiquitous networks: Authentication, Access Control and Key Negotiation. Our proposal is also able to fully satisfy the security requirements for users of the network applications and services in Ambient Networks (1), (2).