Data Mining - Concepts and Techniques.

Data Mining Practical Machine Learning Tools and Techniques

Topology control in a sensor network balances load on sensor nodes and increases network scalability and lifetime. Clustering sensor nodes is an effective topology control approach. We propose a novel distributed clustering approach for long-lived ad hoc sensor networks. Our proposed approach does not make any assumptions about the presence of infrastructure or about node capabilities, other than the availability of multiple power levels in sensor nodes. We present a protocol, HEED (Hybrid Energy-Efficient Distributed clustering), that periodically selects cluster heads according to a hybrid of the node residual energy and a secondary parameter, such as node proximity to its neighbors or node degree. HEED terminates in O(1) iterations, incurs low message overhead, and achieves fairly uniform cluster head distribution across the network. We prove that, with appropriate bounds on node density and intracluster and intercluster transmission ranges, HEED can asymptotically almost surely guarantee connectivity of clustered networks. Simulation results demonstrate that our proposed approach is effective in prolonging the network lifetime and supporting scalable data aggregation.

/pdf/heed-a-hybrid-energy-efficient-distributed-clustering-4c3cjgsfv9.pdf

HEED: a hybrid, energy-efficient, distributed clustering approach for ad hoc sensor networks

http://cpham.perso.univ-pau.fr/ENSEIGNEMENT/PAU-UPPA/RESA-M2/Clustering-abasi.pdf

A survey on clustering algorithms for wireless sensor networks

Topology Control (TC) is one of the most important techniques used in wireless ad hoc and sensor networks to reduce energy consumption (which is essential to extend the network operational time) and radio interference (with a positive effect on the network traffic carrying capacity). The goal of this technique is to control the topology of the graph representing the communication links between network nodes with the purpose of maintaining some global graph property (e.g., connectivity), while reducing energy consumption and/or interference that are strictly related to the nodes' transmitting range. In this article, we state several problems related to topology control in wireless ad hoc and sensor networks, and we survey state-of-the-art solutions which have been proposed to tackle them. We also outline several directions for further research which we hope will motivate researchers to undertake additional studies in this field.

/pdf/topology-control-in-wireless-ad-hoc-and-sensor-networks-3e17u396zt.pdf

Topology Control in Wireless Ad Hoc and Sensor Networks

The Ripple credit network has emerged as a payment backbone with key advantages for financial institutions and the remittance industry. Its path-based IOweYou (IOU) settlements across different (crypto)currencies conceptually distinguishes the Ripple blockchain from cryptocurrencies, and makes it highly suitable to an orthogonal yet vast set of applications in the remittance world for cross-border transactions and beyond. 
This work studies the structure and evolution of the Ripple network since its inception, and investigates its vulnerability to devilry attacks that affect the credit of linnet users' wallets. We find that about 13M USD are at risk in the current Ripple network due to inappropriate configuration of the rippling flag on credit links, facilitating undesired redistribution of credit across those links. Although the Ripple network has grown around a few highly connected hub (gateway) wallets that constitute the network's core and provide high liquidity to users, such a credit link distribution results in a user base of around 112,000 wallets that can be financially isolated by as few as 10 highly connected gateway wallets. Indeed, today about 4.9M USD cannot be withdrawn by their owners from the Ripple network due to PayRoutes, a gateway tagged as faulty by the Ripple community. Finally, we observe that stale exchange offers pose a real problem, and exchanges (market makers) have not always been vigilant about periodically updating their exchange offers according to current real-world exchange rates. For example, stale offers were used by 84 Ripple wallets to gain more than 4.5M USD from mid-July to mid-August 2017. Our findings should prompt the Ripple community to improve the health of the network by educating its users on increasing their connectivity, and by appropriately maintaining the credit limits, rippling flags, and exchange offers on their credit links.

Mind Your Credit: Assessing the Health of the Ripple Credit Network

In wireless networks, the implicit assumption which TCP makes that losses indicate network congestion is no longer valid. Losses in wireless networks can result from bit errors, fading and handoffs. There are two different approaches to improve TCP performance in case of wireless losses: (1) hide non-congestion-related losses from the TCP sender, using either TCP-aware or TCP-unaware reliable link layer protocols, or using split connections with separate wireline and wireless TCP connections, or (2) adapt the TCP sender to realize that some losses are not due to congestion, e.g., using selective acknowledgments or explicit loss notification. In this paper, we classify popular mechanisms that have been recently proposed to solve the wireless transport problem, and contrast them according to their complexity, ease of deployment, and performance in different scenarios. We conclude that some TCP sender adaptations work well for certain environments only, while others are generally useful. Local recovery works best when the wireless link delay is small, and split connection schemes allow application/transport level optimizations, but exhibit overhead and lack robustness. Keywords— TCP/IP, congestion control, wireless networks, satellite networks

/pdf/tcp-over-wireless-links-mechanisms-and-implications-2odp5l9tp4.pdf

TCP over Wireless Links: Mechanisms and Implications

Asynchronous transfer mode (ATM) is the new generation of computer and communication networks that are being deployed throughout the telecommunication industry as well as in campus backbones. ATM technology distinguishes itself from the previous networking protocols in that it has the latest traffic management technology and thus allows guaranteeing delay, throughput, and other performance measures. This in turn, allows users to integrate voice, video, and data on the same network. Available bit rate (ABR) service in ATM has been designed to fairly distribute all unused capacity to data traffic and is specified in the ATM Forum's Traffic Management (TM4.0) standard. This paper will describe the OPNET models that have been developed for ATM and ABR design and analysis.

Modeling Traffic Management in ATM Networks with OPNET

Internet Service Providers (ISPs) need to balance multiple opposing objectives. On one hand, they strive to offer innovative services to obtain competitive advantages; on the other, they have to interconnect with potentially competing ISPs to achieve reachability, and coordinate with them for certain services. The complexity of balancing these objectives is reflected in the diversity of policies of the Border Gateway Protocol (BGP), the standard inter-domain routing protocol. Unforeseen interactions among the BGP policies of different ISPs can cause routing anomalies. In this work, we propose a methodology to allow ISPs to check their BGP policy configurations for guaranteed convergence to a single stable state. This requires that a set of ISPs share their configurations with each other, or with a trusted third party. Compared to previous approaches to BGP safety, we (1) allow ISPs to use a richer set of policies, (2) do not modify the BGP protocol itself, and (3) detect not only instability, but also multiple stable states. Our methodology is based on the extension of current theoretical frameworks to relax their constraints and use incomplete data. We believe that this provides a rigorous foundation for the design and implementation of safety checking tools.

/pdf/detecting-unsafe-bgp-policies-in-a-flexible-world-26d7qlkr2z.pdf

Detecting unsafe BGP policies in a flexible world

We design an efficient on-line approach, FlowMate, for partitioning flows at a busy server into flow groups that share bottlenecks. These groups are periodically input to congestion coordination, aggregation, load balancing, admission control, or pricing modules. FlowMate uses in-band packet delay measurements to the receivers to determine shared bottlenecks among flows. Packet delay information is piggybacked on returning feedback, or, if impossible, flow (e.g., TCP) round trip time estimates are used. We simulate FlowMate to examine the effect of network load, traffic burstiness, network buffer sizes, and packet drop policies on partitioning correctness. Our results demonstrate accurate partitioning of medium to long-lived flows even under heavy load and self-similar background traffic. Experiments with HTTP/1.1 flows demonstrate difficulties in partitioning bursty foreground traffic. We also study fairness of coordinated congestion management when integrated with FlowMate.

/pdf/on-efficient-on-line-grouping-of-flows-with-shared-4up4w1u1n3.pdf

Sonia Fahmy

Papers

Mind Your Credit: Assessing the Health of the Ripple Credit Network

TCP over Wireless Links: Mechanisms and Implications

Modeling Traffic Management in ATM Networks with OPNET

Detecting unsafe BGP policies in a flexible world

On efficient on-line grouping of flows with shared bottlenecks at loaded servers