Congduc Pham

Enforcing QoS in scientific workflow systems enacted over Cloud infrastructures

The ability to support Quality of Service (QoS) constraints is an important requirement in some scientific applications. With the increasing use of Cloud computing infrastructures, where access to resources is shared, dynamic and provisioned on-demand, identifying how QoS constraints can be supported becomes an important challenge. However, access to dedicated resources is often not possible in existing Cloud deployments and limited QoS guarantees are provided by many commercial providers (often restricted to error rate and availability, rather than particular QoS metrics such as latency or access time). We propose a workflow system architecture which enforces QoS for the simultaneous execution of multiple scientific workflows over a shared infrastructure (such as a Cloud environment). Our approach involves multiple pipeline workflow instances, with each instance having its own QoS requirements. These workflows are composed of a number of stages, with each stage being mapped to one or more physical resources. A stage involves a combination of data access, computation and data transfer capability. A token bucket-based data throttling framework is embedded into the workflow system architecture. Each workflow instance stage regulates the amount of data that is injected into the shared resources, allowing for bursts of data to be injected while at the same time providing isolation of workflow streams. We demonstrate our approach by using the Montage workflow, and develop a Reference net model of the workflow.

Performance study of multiple cover-set strategies for mission-critical video surveillance with wireless video sensors

A Wireless Video Sensor Network (WVSN) consists of a set of sensor nodes equipped with miniaturized video cameras. Unlike omni-directional sensors, the sensing region of a video node is limited to the field of view of its camera. In this paper, we study the problem of coverage by video sensors in randomly deployed WVSN. We focus on the performance of various fast cover set construction strategies for enabling efficient scheduling of nodes in mission-critical surveillance applications. Simulation results shows the performance of the various strategies in terms of percentage of coverage, network lifetime, intrusion stealth time and number of intrusion detection.

Communication performances of IEEE 802.15.4 wireless sensor motes for data-intensive applications

In this paper, we are investigating the communication performances of low-resources sensor motes that are commonly found in recent smart cities test-beds or used by the research community. We focus here on 802.15.4 radio and we will present a performance study of sending and receiving capabilities of Libelium WaspMote, Arduino-based motes, Telosb-based motes, MicaZ motes and iMote2 motes when a large number of packets needs to be sent from sources to sink node. We provide measures for the minimum time spent in send procedure, minimum time needed to read data into application memory space and maximum sender/receiver throughput. We will highlight the main sources of delays assuming no flow control nor congestion control to determine the best case performance level. Our contribution is therefore in determining the maximum realistic level of performance for commonly found mote platforms in order to predict end-to-end performances for surveillance applications. Finally, we illustrate our study with an image transmission test case for intrusion detection surveillance applications.

Load repartition for congestion control in multimedia wireless sensor networks with multipath routing

Wireless sensor networks hold a great potential in the deployment of several applications of a paramount importance in our daily life. Video sensors are able to improve a number of these applications where new approaches adapted to both wireless sensor networks and video transport specific characteristics are required. The aim of this work is to provide the necessary bandwidth and to alleviate the congestion problem to video streaming. In this paper, we investigate various load repartition strategies for congestion control mechanism on top of a multipath routing feature. Simulations are performed in order to get insight into the performances of our proposals.

Active Networking Support for the Grid

Grid computing is a promising way to aggregate geographically distant machines and to allow them to work together to solve large problems.After studying Grid network requirements, we observe that the network must take part of the Grid computing session to provide intelligent adaptative transport of Grid data streams.By proposing new intelligent dynamic services, active network can be the perfect companion to easily and efficiently deploy and maintain Grid environments and applications.This paper presents the Active Grid Architecture (A-Grid) which focus on active networks adaptation for supporting Grid environments and applications.We focus the benefit of active networking for the grid on three aspects: High performance and dynamic active services, Active Reliable Multicast, and Active Quality of Service.

Robust transport protocol for dynamic high-speed networks: enhancing the XCP approach

Transport protocols have the difficult task of providing reliability and fair sharing of the bandwidth to end-users. In this paper, we focus on very dynamic high-speed networks where the available best-effort bandwidth for regulated traffics can vary over time. Foreseen problems introduced by such highly dynamic environments are inefficiency due to convergence time and high amount of packet losses due to dramatic reductions of the available bandwidth. Therefore end-to-end solutions show their limitations for exploiting the current very high-speed infrastructures. XCP is a promising approach as the evolution of the sender congestion window size is dictated by the routers. However, as the XCP sender relies on the returned ACKs to adapt its congestion window size, XCP performances can be affected if many losses occur on the reverse path. This paper proposes to calculate the congestion window size at the receiver side and to overcome the problem of ACK losses. The result is a more robust XCP transport protocol, capable of achieving a high level of performance in very dynamic high-speed networks, thus able to function in a broader range of network conditions.

Dynamic replier active reliable multicast (DyRAM)

Desirable features of reliable multicast include low end-to-end delays, high throughput and scalability, and meeting these objectives is not an easy task. We propose a receiver-based (replier) local recovery multicast protocol with dynamic repliers elected on a per-packet basis. Designed to provide an efficient reliable multicast service without any cache facilities in the multicast tree, our approach, denoted DyRAM, uses low-overhead active services in routers. After presentation of the protocol and some design and implementation issues, the paper compares DyRAM to ARM, the nearest active reliable multicast protocol in term of functionalities proposed in the active multicast community. Simulation results show that DyRAM performs much better than an ARM-like protocol which needs a significant amount of cache to exhibit performances. Additionally, in the case that some cache is available for DyRAM and ARM, the study shows that DyRAM always performs better than ARM.

Dynamic scheduling of cover-sets in randomly deployed Wireless Video Sensor Networks for surveillance applications

A Wireless Video Sensor Network (WVSN) consists of a set of sensor nodes equipped with miniaturized video cameras. Unlike omni-directional sensors, the sensing region of a video node is limited to the field of view of its camera. Power conservation and coverage is an important issue in such wireless video networks, especially in the context of surveillance applications which is the focus of the article. In this paper, we address the area coverage problem of scheduling the activity of randomly deployed nodes to extend the network lifetime. We present a distributed algorithm for area coverage (no known targets). Moreover, we show that our approach reduces inherent ambiguities when it is necessary. Simulation results are also presented to verify the performance of the proposed approach.

NXG03-4: XCP-i : eXplicit Control Protocol for Heterogeneous Inter-Networking of High-Speed Networks

XCP is a transport protocol that uses the assistance of specialized routers to very accurately determine the available bandwidth along the path from the source to the destination. In this way, XCP efficiently controls the senders congestion window size thus avoiding the traditional slow-start and congestion avoidance phase. However, XCP requires the collaboration of all the routers on the data path which is almost impossible to achieve in an incremental deployment scenario of XCP. It has been shown that XCP behaves badly, worse than TCP, in the presence of non-XCP routers thus limiting dramatically the benefit of having XCP running in some parts of the network. In this paper, we address this problem and propose XCP-i which is operable on an internetwork consisting of XCP routers and traditional IP routers without loosing the benefit of the XCP control laws. The simulation results on a number of topologies that reflect the various scenario of incremental deployment on the Internet show that although XCP-i performances depend on available bandwidth estimation accuracy, XCP-i still outperforms TCP on high-speed links.

Resource management for bursty streams on multi-tenancy cloud environments

The number of applications that need to process data continuously over long periods of time has increased significantly over recent years. The emerging Internet of Things and Smart Cities scenarios also confirm the requirement for real time, large scale data processing. When data from multiple sources are processed over a shared distributed computing infrastructure, it is necessary to provide some Quality of Service (QoS) guarantees for each data stream, specified in a Service Level Agreement (SLA). SLAs identify the price that a user must pay to achieve the required QoS, and the penalty that the provider will pay the user in case of QoS violation. Assuming maximization of revenue as a Cloud providers objective, then it must decide which streams to accept for storage and analysis; and how many resources to allocate for each stream. When the real-time requirements demand a rapid reaction, dynamic resource provisioning policies and mechanisms may not be useful, since the delays and overheads incurred might be too high. Alternatively, idle resources that were initially allocated for other streams could be re-allocated, avoiding subsequent penalties. In this paper, we propose a system architecture for supporting QoS for concurrent data streams to be composed of self-regulating nodes. Each node features an envelope process for regulating and controlling data access and a resource manager to enable resource allocation, and selective SLA violations, while maximizing revenue. Our resource manager, based on a shared token bucket, enables: (i) the re-distribution of unused resources amongst data streams; and (ii) a dynamic re-allocation of resources to streams likely to generate greater profit for the provider. We extend previous work by providing a Petri-net based model of system components, and we evaluate our approach on an OpenNebula-based Cloud infrastructure. We provide a system for simultaneous bursty data streams on shared Clouds.We enforce QoS based on a profit-based resource management model.We provide real experiments within an OpenNebula based data centre.