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Articles 52471 - 52500 of 58244

Full-Text Articles in Physical Sciences and Mathematics

An Integrated Design-Object Modeling Environment -- Pluggable Metamodel Mechanism --, Masaharu Yoshioka, Takayuki Sekiya, Tetsuo Tomiyama Jan 2001

An Integrated Design-Object Modeling Environment -- Pluggable Metamodel Mechanism --, Masaharu Yoshioka, Takayuki Sekiya, Tetsuo Tomiyama

Turkish Journal of Electrical Engineering and Computer Sciences

We propose a new integrated computational environment to support design object modeling, during engineering design process that requires a variety of design object models, such as a geometric model, a control model, and a finite element model. To integrate multiple design object models, we have developed a mechanism called a metamodel mechanism that maintains consistency among various models. The metamodel mechanism represents relationships among concepts used in these models and is useful, for example, to conduct concurrent engineering practices. In this framework, we formalize a design process as operations to the metamodel. This paper expands the concept of the metamodel …

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All-Optical Networking, Altan Koçyi̇ği̇t, Demeter Gökişik, Semi̇h Bi̇lgen Jan 2001

All-Optical Networking, Altan Koçyi̇ği̇t, Demeter Gökişik, Semi̇h Bi̇lgen

Turkish Journal of Electrical Engineering and Computer Sciences

A survey of recent literature on all optical networking is presented. Starting from multiplexing techniques and topological features, network design and performance issues are reviewed. Particular attention is devoted to Wavelength Division Multiplexing (WDM) networks. Static and dynamic solutions of the routing and wavelength assignment (RWA) problem are considered. Issues of current research are summarized.

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Performance Evaluation Of Safer K-64 And S-Boxes Of The Safer Family, Ekrem Aras, Melek D. Yücel Jan 2001

Performance Evaluation Of Safer K-64 And S-Boxes Of The Safer Family, Ekrem Aras, Melek D. Yücel

Turkish Journal of Electrical Engineering and Computer Sciences

If the characteristics of s-boxes of the SAFER family of ciphers are examined for the criteria of strict avalanche, bit independence, and XOR table distribution, experiments show that the ``exponentiating'' s-box has a weakness for an input difference of 128 (=10000000_{2}) and the ``logarithm-taking'' s-box has a weakness for an input difference of 253 (=11111101_{2}). However, since these experiments are performed by isolating the s-boxes from the general structure, they do not necessarily indicate a weakness in the overall algorithm. We propose a quick and rough test method, called the avalanche weight distribution criterion, to evaluate the overall performance of …

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Virtual Path Bandwidth Distribution And Capacity Allocation With Bandwidth Sharing, Karen Marie Anewalt Jan 2001

Virtual Path Bandwidth Distribution And Capacity Allocation With Bandwidth Sharing, Karen Marie Anewalt

Dissertations, Theses, and Masters Projects

Broadband high-speed networks, such as B-ISDN, are expected to play a dominant role in the future of networking due to their capability to service a variety of traffic types with very different bandwidth requirements such as video, voice and data. to increase network efficiency in B-ISDN and other such connection oriented networks, the concept of a virtual path (VP) has been proposed and studied in the literature. A VP is a permanent or semi-permanent reservation of capacity between two nodes. Using VPs can potentially reduce call setup delays, simplify hardware, provide quality of service performance guarantees, and reduce disruption in …

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Performance Evaluation Of Hybrid Coding Of Images Using Wavelet Transform And Predictive Coding, S. R. Subramanya, Chaman Sabharwal Jan 2001

Performance Evaluation Of Hybrid Coding Of Images Using Wavelet Transform And Predictive Coding, S. R. Subramanya, Chaman Sabharwal

Computer Science Faculty Research & Creative Works

Image compression techniques are necessary for the storage of huge amounts of digital images using reasonable amounts of space, and for their transmission with limited bandwidth. Several techniques such as predictive coding, transform coding, subband coding, wavelet coding, and vector quantization have been used in image coding. While each technique has some advantages, most practical systems use hybrid techniques which incorporate more than one scheme. They combine the advantages of the individual schemes and enhance the coding effectiveness. This paper proposes and evaluates a hybrid coding scheme for images using wavelet transforms and predictive coding. The performance evaluation is done …

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Local Search And Encoding Schemes For Soft Constraint Minimization Problems, Michael P. Moran, Weixiong Zhang Jan 2001

Local Search And Encoding Schemes For Soft Constraint Minimization Problems, Michael P. Moran, Weixiong Zhang

All Computer Science and Engineering Research

Soft constraint minimization problems (SCMPs) contain hard constraints that cannot be violated and soft constraints that may be violated but carry penalties if not satisfied. In this paper, we first extend local search, WalkSAT in particular, to SCMPs and study the existing SAT encoding schemes for SCMPs. We propose a general encoding method called k-encoding. We then investigate the effects of local search neiborhood structures introduced by encoding schemes and analyze the anytime performance of extended WalkSAT using different encoding methods. Our experimental results on various graph coloring problems show that a direct extension of WalkSAT is most effective, and …

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Fuzzycast: Media Broadcasting For Multiple Asynchronous Receivers, Marcel Waldvogel, Wei Deng, Ramaprabhu Janakiraman Jan 2001

Fuzzycast: Media Broadcasting For Multiple Asynchronous Receivers, Marcel Waldvogel, Wei Deng, Ramaprabhu Janakiraman

All Computer Science and Engineering Research

When using an on-demand media streaming system on top of a network with Multicast support, it is sometimes more efficient to use broadcast to distribute popular content. There has been a lot of research in broadcasting on-demand content to multiple, asynchronous receivers. In this paper, we propose a family of novel, practical techniques for broadcasting on-demand media, which achieve lowest known server/network bandwidth usage and I/O efficient client buffer management, while retaining the simplicity of a frame-based single channel scheme.

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A Proposal For A Scalable Internet Multicast Architecture, Sherlia Shi Jan 2001

A Proposal For A Scalable Internet Multicast Architecture, Sherlia Shi

All Computer Science and Engineering Research

We propose a new network and system architecture for multicast in the Internet. Our main objectives are to find a cost-effective way to scale to a large number of multicast groups whose members are geographically dispersed, and to enable small and less capable devices to participate in group communications. In order to preserve the efficiency of data distribution gained by multicast, while avoiding the control complexity previously exhibited by IP multicast, we propose the use of an overlay network for multicast services. We construct "virtual" multicast trees, which consist of unicast connections joining multicast servers in the network. These servers …

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Formal Specification And Design Of Mobile Systems, Gruia-Catalin Roman, Christine Julien, Qingfeng Huang Jan 2001

Formal Specification And Design Of Mobile Systems, Gruia-Catalin Roman, Christine Julien, Qingfeng Huang

All Computer Science and Engineering Research

Termination detection, a classical problem in distributed computing, is revisited in the new setting provided by the emerging mobile computing technology. A simple solution tailored for use in ad hoc networks is employed as a vehicle for demonstrating the applicability of formal requirements and design strategies to the new field of mobile computing. The approach is based on well understood techniquest in specification refinement, but the methodology is tailored to mobile applications and helps designers address novel concerns such as the mobility of hosts, transient interactions, and specific coordination constructs. The proof logic and programming notation of Mobile UNITY provide …

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Aggregated Hierarchical Multicast For Active Networks, Tilman Wolf, Sumi Y. Choi Jan 2001

Aggregated Hierarchical Multicast For Active Networks, Tilman Wolf, Sumi Y. Choi

All Computer Science and Engineering Research

Active Networking is the basis for a range of new and innovative applications that make use of computational resources inside network routers. One such application is Aggregated Hierarchical Multicast, which aims at implementing efficient many-to-many communication. In certain scenarios it is possible to transmit less accurate, aggregated data and thus achieve better scalability. Using Active Networks, this aggregation computation can be done transparently by network routers without end system support. We present how aggregated data streams can be structured in a hierarchical fashion to allow easy access of data at the desired aggregation level. We introduce two application examples to …

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Dres: Internet Resource Management Using Deferred Reservations, Samphel Norden Jan 2001

Dres: Internet Resource Management Using Deferred Reservations, Samphel Norden

All Computer Science and Engineering Research

In this proposal, we consider the problem of resource reservation for Integrated Services (IntServ) and Differentiated Services (DiffServ) networks. Current approaches for resource reservation in INtegrated Service Networks adopt an all-or-nothing approach, where partially acquired resources must be released if resources are not available at all routers on the chosen path. Furthermore, under high load, end-systems must retry requests repeatedly leading to inefficient allocation and increased traffic. We propose a new approach called Deferred REServation (DERS) that substantially improves performance (reduces the overall cell rejection probability and increases link utilization) over the all-or-nothing reservation approach. Call admissibility is increased by …

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Fast Incremental Crc Updates For Ip Over Atm Networks, Florian Braun, Marcel Waldvogel Jan 2001

Fast Incremental Crc Updates For Ip Over Atm Networks, Florian Braun, Marcel Waldvogel

All Computer Science and Engineering Research

In response to the increasing network speeds, many operations in IP routers and similar devices are being made more efficient. With the advances in other areas of packet processing, the verification and regeneration of cyclic redundancy check (CRC) codes of the data link layer is likely to become a bottleneck in the near future. In this paper, we present a mechanism to defer CRC verification without compromising reliability. This opens the possibility of incremental updates of the CRC. We introduce a new high-speed technique and present efficient implementation, speeding up CRC processing by a factor of 15. Although the paper …

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Layered Protocol Wrappers For Internet Packet Processing In Reconfigurable Hardware, Florian Braun, John Lockwood, Marcel Waldvogel Jan 2001

Layered Protocol Wrappers For Internet Packet Processing In Reconfigurable Hardware, Florian Braun, John Lockwood, Marcel Waldvogel

All Computer Science and Engineering Research

The ongoing increases of line speed in the Internet backbone combined with the need for increased functionality of network devices presents a major challenge. These demands call for the use of reprogrammable hardware to provide the required flexible, high-speed functionality, at all network layers. The Field Programmable Port Extender (FPX) provides such an environment for development of networking components in reprogrammable hardware. We present a framework to streamline and simplify networking applications that process ATM cells, AAL5 frames, Internet Protocol (IP) packets and UDP datagrams directly in hardware.

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Obiwan - An Internet Protocol Router In Reconfigurable Hardware, Florian Braun, Marcel Waldvogel, John Lockwood Jan 2001

Obiwan - An Internet Protocol Router In Reconfigurable Hardware, Florian Braun, Marcel Waldvogel, John Lockwood

All Computer Science and Engineering Research

The ongoing exponential increase of line speed in the Internet and combined with the uncountable requests for increased functionality of network devices presents a major challenge. These demands call for the use of reprogrammable hardware to provide the required flexible high-speed functionaltiy. The Field Programmable Port Extender (FPX) provides such an environment for development of networking components in reprogrammable hardware. We present the high-speed IP routing components in reprogrammable hardware. We present the high-speed IP routing module "OBIWAN" (Optimal Binary search IP lookup for Wide Area Networks) built on top of an IP processing framework.

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Phase Transitions And Backbones Of Constraint Minimization Problems, Weixiong Zhang Jan 2001

Phase Transitions And Backbones Of Constraint Minimization Problems, Weixiong Zhang

All Computer Science and Engineering Research

Many real-world problems involve constraints that cannot be all satisfied. The goal toward an overconstrained problem is to find solutions minimizing the total number of constraints violated. We call such a problem constraint minimization problem (CMP). We study the behavior of the phase transitions and backbones of CMP. We first investigate the relationship between the phase transitions of Boolean satisfiability, or precisely 3-SAT (a well-studied NP-complete decision problem), and the phase transitions of MAX 3-SAT (an NP-hard optimization problem). To bridge the gap between the easy-hard-easy phase transitions of 3-SAT, in which solutions of bounded quality, e.g., solutions with at …

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Parbit: A Tool To Transform Bitfiles To Implement Partial Reconfiguration Of Field Programmable Gate Arrays (Fpgas), Edson L. Horta, John W. Lockwood Jan 2001

Parbit: A Tool To Transform Bitfiles To Implement Partial Reconfiguration Of Field Programmable Gate Arrays (Fpgas), Edson L. Horta, John W. Lockwood

All Computer Science and Engineering Research

Field Programmable Gate Arrays (FPGAs) can be partially reconfigured to implement Dynamically loadable Hardware Plugin (DHP) modules. A tool called PARBIT has been developed that transforms FPGA configuration bitfiles to enable DHP modules. With this tool it is possible to define a partial reconfigurable area inside the FPGA and download it into a specified region of the FPGA device. One or more DHPs, with different sizes can be implemented using PARBIT.

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The Fpx Kcpsm Module: An Embedded, Reconfigurable Active Processing Module For The Field Programmable Port Extender (Fpx), Henry Fu, John W. Lockwood Jan 2001

The Fpx Kcpsm Module: An Embedded, Reconfigurable Active Processing Module For The Field Programmable Port Extender (Fpx), Henry Fu, John W. Lockwood

All Computer Science and Engineering Research

While hardware plugins are well suited for processing data with high throughput, software plugins are well suited for implementing complex control functions. A plugin module has been implemented for the FPX that executes software on an embedded soft-core processor. By including this module in an FPX design, it is possible to implement active networking functions on the FPX using both hardware and software. The KCPSM, an 8-bit microcontroller developed by Xilinx Corp., has been embedded into an FPX module. The module includes circuits to be reprogrammed over the network and to execute new programs between the processing of data packerts. …

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Generalized Rad Module Interface Specification Of The Field-Programmable Port Extender (Fpx) Version 2.0, David E. Taylor, John W. Lockwood, Sarang Dharmapurikar Jan 2001

Generalized Rad Module Interface Specification Of The Field-Programmable Port Extender (Fpx) Version 2.0, David E. Taylor, John W. Lockwood, Sarang Dharmapurikar

All Computer Science and Engineering Research

The Field-programmable Port eXtender (FPX) provides dynamic, fast, and flexible mechanisms to process data streams at the ports of the Washington University Gigabit Switch (WUGS-20). By performing all computations in FPGA hardware, cells and packets can be processed at the full line speed of the transmission interface, currently 2.4 Gbits/sec. In order to design and implement portable hardware modules for the Reprogrammable Application Devide (RAD) on the FPX board, all modules should conform to a standard interface. This standard interface specifies how modules receive and transmit ATM cells of data flows, prevent data loss during reconfiguration, and access off-chip memory. …

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Rad Module Infrastructure Of The Field-Programmable Port Extender (Fpx) Version 2.0, David E. Taylor, John W. Lockwood, Naji Naufel Jan 2001

Rad Module Infrastructure Of The Field-Programmable Port Extender (Fpx) Version 2.0, David E. Taylor, John W. Lockwood, Naji Naufel

All Computer Science and Engineering Research

The Field-programmable Port eXtender (FPX) provides dynamic, fast, and flexible mechanisms to process data streams at the ports of the Washington University Gigabit Switch (WUGS-20). In order to facilitate the design and implementation of portable hardware modules for the Reprogrammable Application Device (RAD) on the FPX board, infrastructure components have been developed. These components abstract application module designers from device-specific timing specifications of off-chip memory devices, as well as processing system-level control cells. This document describes the design and internal functionality of the infrastructure components and is intended as a reference for future component revisions and additions. Application module designers …

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The Smart Port Card: An Embedded Unix Processor Architecture For Network Management And Active Networking, John D. Dehart, William D. Richard, Edward W. Spitznagel, David E. Taylor Jan 2001

The Smart Port Card: An Embedded Unix Processor Architecture For Network Management And Active Networking, John D. Dehart, William D. Richard, Edward W. Spitznagel, David E. Taylor

All Computer Science and Engineering Research

This paper describes the architecture of the Smart Port Card (SPC) designed for use with the Washington University Gigabit Switch. The SPC uses an embedded Intel Pentium processor running open-source NetBSD to support network management and active networking applications. The SPC physically connects between a switch port and a normal link adapter, allowing cell streams to be processed as they enter or leave the switch. In addition to the hardware architecture, this paper describes current and future applications for the SPC.

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Routing In Overlay Multicast Networks, Sherlia Y. Shi, Jonathan S. Turner Jan 2001

Routing In Overlay Multicast Networks, Sherlia Y. Shi, Jonathan S. Turner

All Computer Science and Engineering Research

Multicast servises can be provided either as a basic network service or as an application-layer service. Higher level multicast implementations often provide more sophisticated features, and since they don't require network supoprt for multicast, they can provide multicast services, where no network layer support is available. Overlay multicast networks offer an intermediate option, potentially combining the flexibility and advanced features of application layer multicast with the greater efficiency of network layer multicast. Overlay multicast networks play an important role in the Internet. Indeed, since Internet Service Providers have been slow to enable IP multicast in their networks, Internet multicast is …

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Implementation Of An Open Multi-Service Router, Fred Kuhns, John Dehart, Ralph Keller, John Lockwood, Prashanth Papu, Jyoti Parwatikar, Ed Spitznagel, David Richard, David Taylor, Jon Turner, Ken Wong Jan 2001

Implementation Of An Open Multi-Service Router, Fred Kuhns, John Dehart, Ralph Keller, John Lockwood, Prashanth Papu, Jyoti Parwatikar, Ed Spitznagel, David Richard, David Taylor, Jon Turner, Ken Wong

All Computer Science and Engineering Research

This paper describes the design, implementation, and performance of an open, high-performance, dynamically reconfigurable Multi-Service Router (MSR) being developed at Washington University in St. Louis. This router provides an experimentation platform for research on protocols, router software, and hardware design, network management, quality of service and advanced applications. The MSR has been designed to be flexible, without sacrificing performance. It support gigabit links and uses a scalable architecture suitable for supporting hundreds or even thousands of links. The MSR's flexibility makes it an ideal platform for experimental research on dynamically extensible networks that implement higher level functions in direct support …

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Design Of Wavelength Converting Switches For Optical Burst Switching, Jeyashankher Ramamirtham, Jonathan Turner Jan 2001

Design Of Wavelength Converting Switches For Optical Burst Switching, Jeyashankher Ramamirtham, Jonathan Turner

All Computer Science and Engineering Research

Optical Burst Switching (OBS) is an experimental network technology that enables the construction of very high capacity routers, using optical data paths and electronic control. In this paper, we study two designs for wavelength converting switches that are suitable for use in optical burst switching systems and evaluate their performance. Both designs use tunable lasers to implement wavelength conversion. One is strictly nonblocking design, that also requires optical crossbars. The second substitutes Wavelength Grating Routers (WGR) for the optical crossbars, reducing cost, but introducing some potential for blocking. We show how the routing problem for the WGR-based switches can be …

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Efficient Queue Management For Tcp Flows, Anshul Kantawala, Jonathan Turner Jan 2001

Efficient Queue Management For Tcp Flows, Anshul Kantawala, Jonathan Turner

All Computer Science and Engineering Research

Packets in the Internet can experience large queueing delays during busy periods. Backbone routers are generally engineered to have large buffers, in which packets may wait as long as half a second (assuming FIFO service, longer otherwise). During congestion periods, these bufferfs may stay close to full, subjecting packets to long delays, even when the intrinsic latency of the path is relatively small. This paper studies the performance improvements that can be obtained by using more sophisticated packet schedulers, than are typical of Internet routers. The results show that the large buffers found in WAN routers ocntribute only marginally to …

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Performance Of Deferred Reservations In Data Networks, Samphel Norden, Jonathan Turner Jan 2001

Performance Of Deferred Reservations In Data Networks, Samphel Norden, Jonathan Turner

All Computer Science and Engineering Research

This paper studies the performance of deferred resource reservation in data networks. Conventional resource reservation protocols, such as PNNI and RSVP adopt an all-or-nothing approach, where partially acquired resources must be released if resources are not available at all links on the chosen path. During periods of high network load, this leads users to retry requests repeatedly, adding control traffic at exactly the time when the network's capacity to process that control traffic is exhausted. Deferred REServation (DRES) can significantly improve performance by reducing the overall call rejection probability, allowing more traffic to be carried, using the same resources. Call …

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Synthesizable Design Of A Multi-Module Memory Controller, Sarang Dharmapurikar, John W. Lockwood Jan 2001

Synthesizable Design Of A Multi-Module Memory Controller, Sarang Dharmapurikar, John W. Lockwood

All Computer Science and Engineering Research

Random Access Memory (RAM) is a common resources needed by networking hardware modules. Synchronous Dynamic RAM (SDRAM) provides a cost effective solution for such data storage. As the packet processing speeds in the hardware increase memory throughput can be a bottleneck to achieve overall high performance. Typically there are multiple hardware modules which perform different operations on the packet payload and hence all try to access the common packet buffer simultaneously. This gives rise to a need for a memory controller which arbitrates between the memory requests made by different modules and maximizes the memory throughput. This paper discusses the …

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Network Abstractions For Context-Aware Mobile Computing, Gruia-Catalin Roman, Christine Julien, Qingfeng Huang Jan 2001

Network Abstractions For Context-Aware Mobile Computing, Gruia-Catalin Roman, Christine Julien, Qingfeng Huang

All Computer Science and Engineering Research

Context-Aware computing is characterized by the ability of a software system to continuously adapt its behavior to a changing environment over which it has little or no control. Previous work along these lines presumed a rather narrow definition of context, one that was centered on resources immediately available to the component in question, e.g., communication bandwidth, physical location, etc. This paper explores context-aware computing in the setting of ad hoc networks consisting of numerous mobile hosts that interact with each other opportunistically via transient wireless interconnections. We extend the context to encompass awareness of an entire neighborhood within the ad …

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A Termination Detection Protocol For Use In Mobile Ad Hoc Networks, Gruia-Catalin Roman, Jamie Payton Jan 2001

A Termination Detection Protocol For Use In Mobile Ad Hoc Networks, Gruia-Catalin Roman, Jamie Payton

All Computer Science and Engineering Research

As computing devices become smaller and wireless networking technologies improve, the popularity of mobile computing continues to rise. In today's business world, many consider devices such as cell phones, PDAs, and laptops as essential tools. As these and other devices become increasingly independent of the wired infrastructure, new kinds of applications that assume an ad hoc network infrastructure will need to be deployed. Such a setting poses new challenges for the software developer, e.g., the lack of an established network topology, bandwidth limitations, and frequent disconnections. In this paper, we begin to explore design strategies for developing applications over ad …

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Indra: A Distributed Approach To Network Intrusion Detection And Prevention, Qi Zhang, Ramaprabhu Janakiraman Jan 2001

Indra: A Distributed Approach To Network Intrusion Detection And Prevention, Qi Zhang, Ramaprabhu Janakiraman

All Computer Science and Engineering Research

While advances in computer and communications technology have made the network ubiquitous, they ahve also rendered networked systems vulnerable to malicious attacks orchestrated from a distance. These attacks, usually called cracker attacks or intrusions, start with crackers infiltrating a network through a vulnerable host and then going on to launch further attacks. Crackers depend on increasingly sophisticated techniques like using distributed attack sources. On the other hand, software that guards against them remains rooted in traditional centralized techniques, presenting an easily-targetable single point of failure. Scalable, distributed network intrusion prevention software is sorely needed. We propose Indra - a distributed …

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Relying On Safe Distance To Ensure Consistent Group Membership In Ad Hoc Networks, Qingfeng Huang, Christine Julien, Gruia-Catalin Roman, Ali Hazemi Jan 2001

Relying On Safe Distance To Ensure Consistent Group Membership In Ad Hoc Networks, Qingfeng Huang, Christine Julien, Gruia-Catalin Roman, Ali Hazemi

All Computer Science and Engineering Research

The design of ad hoc mobile applications often requires the availability of a consistent view of the application state among the participating hosts. Such views are important because they simplify both the programming and verification tasks. Essential to constructing a consitent view is the ability to know what hosts are within proximity of each other, i.e., form a group in support of the particular application. In this paper we propose a protocol that allows hosts within communication range to maintain a consistent view of the group membership despite movement and frequent disconnections. The novel features of this protocol are its …

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