3,033 research outputs found
Evaluation study of IEEE 1609.4 performance for safety and non-safety messages dissemination
The IEEE 1609.4 was developed to support multi-channel operation and channel switching procedure in order to provide both safety and non-safety vehicular applications. However, this protocol has some drawback because it does not make efficient usage of channel bandwidth resources for single radio WAVE devices and suffer from high bounded delay and lost packet especially for large-scale networks in terms of the number of active nodes. This paper evaluates IEEE 1609.4 multi-channel protocol performance for safety and non-safety application and compare it with the IEEE 802.11p single channel protocol. Multi-channel and single channel protocols are analyzed in different environments to investigate their performance. By relying on a realistic dataset and using OMNeT++ simulation tool as network simulator, SUMO as traffic simulator and coupling them by employing Veins framework. Performance evaluation results show that the delay of single channel protocol IEEE 802.11p has been degraded 36% compared with multi-channel protocol
Delay Tolerant Networking over the Metropolitan Public Transportation
We discuss MDTN: a delay tolerant application platform built on top of the Public Transportation System (PTS) and able to provide service access while exploiting opportunistic connectivity. Our solution adopts a carrier-based approach where buses act as data collectors for user requests requiring Internet access. Simulations based on real maps and PTS routes with state-of-the-art routing protocols demonstrate that MDTN represents a viable solution for elastic nonreal-time service delivery. Nevertheless, performance indexes of the considered routing policies show that there is no golden rule for optimal performance and a tailored routing strategy is required for each specific case
Driver's visual attention to different categories of roadside advertising signs
Roadside advertising signs are a salient potential source of driver's distraction. Previous research has mainly investigated driver's visual attention to billboards, which represents only one category of advertising signs. In this study, driver's visual attention was assessed in a naturalistic driving setting for six categories of roadside advertising signs: vendor signs, billboards, movable display boards, single and multiple commercial directional signs, and gas price LED displays. Fixation rate, fixation duration, fixation distance and driving speed were assessed in a sample of 15 drivers along a 30-km route including a total of 154 advertising signs belonging to the six categories described above. The role of clearance from the road, elevation, height, width, surface, number and size of characters, total number of characters, side of the road (driving side, opposite side), context (rural, urban), were also considered. Overall 24% of the roadside advertising signs were fixated. Fixation rate was significantly influenced by sign category, clearance from the road and number of characters. Median value for fixation duration was 297 ms. Fixation duration was significantly influenced by speed, elevation from road level, number of medium size characters, and was higher in the rural context. Median value for fixation distance was 58.10 m, and was significantly influenced by advertising sign category, character count and speed
Leveraging Conventional Internet Routing Protocol Behavior to Defeat DDoS and Adverse Networking Conditions
The Internet is a cornerstone of modern society. Yet increasingly devastating attacks against the Internet threaten to undermine the Internet\u27s success at connecting the unconnected. Of all the adversarial campaigns waged against the Internet and the organizations that rely on it, distributed denial of service, or DDoS, tops the list of the most volatile attacks. In recent years, DDoS attacks have been responsible for large swaths of the Internet blacking out, while other attacks have completely overwhelmed key Internet services and websites. Core to the Internet\u27s functionality is the way in which traffic on the Internet gets from one destination to another. The set of rules, or protocol, that defines the way traffic travels the Internet is known as the Border Gateway Protocol, or BGP, the de facto routing protocol on the Internet. Advanced adversaries often target the most used portions of the Internet by flooding the routes benign traffic takes with malicious traffic designed to cause widespread traffic loss to targeted end users and regions. This dissertation focuses on examining the following thesis statement. Rather than seek to redefine the way the Internet works to combat advanced DDoS attacks, we can leverage conventional Internet routing behavior to mitigate modern distributed denial of service attacks.
The research in this work breaks down into a single arc with three independent, but connected thrusts, which demonstrate that the aforementioned thesis is possible, practical, and useful. The first thrust demonstrates that this thesis is possible by building and evaluating Nyx, a system that can protect Internet networks from DDoS using BGP, without an Internet redesign and without cooperation from other networks. This work reveals that Nyx is effective in simulation for protecting Internet networks and end users from the impact of devastating DDoS. The second thrust examines the real-world practicality of Nyx, as well as other systems which rely on real-world BGP behavior. Through a comprehensive set of real-world Internet routing experiments, this second thrust confirms that Nyx works effectively in practice beyond simulation as well as revealing novel insights about the effectiveness of other Internet security defensive and offensive systems. We then follow these experiments by re-evaluating Nyx under the real-world routing constraints we discovered. The third thrust explores the usefulness of Nyx for mitigating DDoS against a crucial industry sector, power generation, by exposing the latent vulnerability of the U.S. power grid to DDoS and how a system such as Nyx can protect electric power utilities. This final thrust finds that the current set of exposed U.S. power facilities are widely vulnerable to DDoS that could induce blackouts, and that Nyx can be leveraged to reduce the impact of these targeted DDoS attacks
QoS Parameter Analysis on AODV and DSDV Protocols in a Wireless Network
Wireless networks are characterized by a lack of infrastructure, and by a random and quickly changing network topology; thus the need for a robust dynamic routing protocol that can accommodate such an environment. To improve the packet delivery ratio of Destination-Sequenced Distance Vector (DSDV) routing protocol in mobile ad hoc networks with high mobility, a message exchange scheme for its invalid route reconstruction is being used. Two protocols AODV and DSDV simulated using NS-2 package and were compared in terms throughput, end to end delay and packet faction delivery varying number of nodes, speed and time. Simulation results show that DSDV compared with AODV, DSDV routing protocol consumes more bandwidth, because of the frequent broadcasting of routing updates. While the AODV is better than DSDV as it doesn’t maintain any routing tables at nodes which results in less overhead and more bandwidth. AODV perform better under high mobility simulations than DSDV. High mobility results in frequent link failures and the overhead involved in updating all the nodes with the new routing information as in DSDV is much more than that involved AODV, where the routes are created as and when required. AODV use on -demand route discovery, but with different routing mechanics. AODV uses routing tables, one route per destination, and destination sequence numbers
Agent-based resource management for grid computing
A computational grid is a hardware and software infrastructure that provides
dependable, consistent, pervasive, and inexpensive access to high-end
computational capability. An ideal grid environment should provide access to the
available resources in a seamless manner. Resource management is an important
infrastructural component of a grid computing environment. The overall aim of
resource management is to efficiently schedule applications that need to utilise the
available resources in the grid environment. Such goals within the high
performance community will rely on accurate performance prediction capabilities.
An existing toolkit, known as PACE (Performance Analysis and Characterisation
Environment), is used to provide quantitative data concerning the performance of
sophisticated applications running on high performance resources. In this thesis an
ASCI (Accelerated Strategic Computing Initiative) kernel application, Sweep3D,
is used to illustrate the PACE performance prediction capabilities. The validation
results show that a reasonable accuracy can be obtained, cross-platform
comparisons can be easily undertaken, and the process benefits from a rapid
evaluation time. While extremely well-suited for managing a locally distributed
multi-computer, the PACE functions do not map well onto a wide-area
environment, where heterogeneity, multiple administrative domains, and communication irregularities dramatically complicate the job of resource
management. Scalability and adaptability are two key challenges that must be
addressed.
In this thesis, an A4 (Agile Architecture and Autonomous Agents) methodology is
introduced for the development of large-scale distributed software systems with
highly dynamic behaviours. An agent is considered to be both a service provider
and a service requestor. Agents are organised into a hierarchy with service
advertisement and discovery capabilities. There are four main performance
metrics for an A4 system: service discovery speed, agent system efficiency,
workload balancing, and discovery success rate.
Coupling the A4 methodology with PACE functions, results in an Agent-based
Resource Management System (ARMS), which is implemented for grid
computing. The PACE functions supply accurate performance information (e. g.
execution time) as input to a local resource scheduler on the fly. At a meta-level,
agents advertise their service information and cooperate with each other to
discover available resources for grid-enabled applications. A Performance
Monitor and Advisor (PMA) is also developed in ARMS to optimise the
performance of the agent behaviours.
The PMA is capable of performance modelling and simulation about the agents in
ARMS and can be used to improve overall system performance. The PMA can
monitor agent behaviours in ARMS and reconfigure them with optimised
strategies, which include the use of ACTs (Agent Capability Tables), limited
service lifetime, limited scope for service advertisement and discovery, agent
mobility and service distribution, etc.
The main contribution of this work is that it provides a methodology and
prototype implementation of a grid Resource Management System (RMS). The
system includes a number of original features that cannot be found in existing
research solutions
Colocation aware content sharing in urban transport
People living in urban areas spend a considerable amount of time on public transport. During
these periods, opportunities for inter-personal networking present themselves, as many of us
now carry electronic devices equipped with Bluetooth or other wireless capabilities. Using these
devices, individuals can share content (e.g., music, news or video clips) with fellow travellers
that happen to be on the same train or bus. Transferring media takes time; in order to maximise
the chances of successfully completing interesting downloads, users should identify neighbours
that possess desirable content and who will travel with them for long-enough periods.
In this thesis, a peer-to-peer content distribution system for wireless devices is proposed,
grounded on three main contributions: (1) a technique to predict colocation durations (2) a
mechanism to exclude poorly performing peers and (3) a library advertisement protocol. The
prediction scheme works on the observation that people have a high degree of regularity in their
movements. Ensuring that content is accurately described and delivered is a challenge in open
networks, requiring the use of a trust framework, to avoid devices that do not behave appropriately.
Content advertising methodologies are investigated, showing their effect on whether
popular material or niche tastes are disseminated.
We first validate our assumptions on synthetic and real datasets, particularly movement
traces that are comparable to urban environments. We then illustrate real world operation using
measurements from mobile devices running our system in the proposed environment. Finally,
we demonstrate experimentally on these traces that our content sharing system significantly
improves data communication efficiency, and file availability compared to naive approaches
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