Browsing by Subject "Computer networks"
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Item A longitudinal study of the diffusion of a computer-based administrative innovation within a university faculty network(Texas Tech University, 1997-12) Durrington, Vance A.Identifying predictors of computer use such as attitude, anxiety, and receptivity to change have been the primary area of interest in instmctional technology. Research relating to the diffusion of innovations in education has been based primarily on looking at these individual characteristics as predictors of use. This dissertation proposes to use social network analysis to study the diffusion of two computer-based administrative innovations within a university faculty network. Methodology issues concerning time of adoption and network nominations were examined as well as the relationship of time of adoption and the number of network nominations received, spatial proximity, and organizational unit proximity. Finally, the diffusion of the innovations was to be analyzed using the dual-classification and T/CM models.Item Item Algorithms for distributed caching and aggregation(2007-12) Tiwari, Mitul; Plaxton, GregIn recent years, there has been an explosion in the amount of distributed data due to the ever decreasing cost of both storage and bandwidth. There is a growing need for automatic distributed data management techniques. The three main areas in dealing with distributed data that we address in this dissertation are (1) cooperative caching, (2) compression caching, and (3) aggregation. First, we address cooperative caching, in which caches cooperate to locate and cache data objects. The benefits of cooperative caching have been demonstrated by various studies. We address a hierarchical generalization of cooperative caching in which caches are arranged as leaf nodes in a hierarchical tree network, and we call this variant Hierarchical Cooperative Caching. We present a deterministic hierarchical generalization of LRU that is constantcompetitive when the capacity blowup is linear in d, the depth of the cache hierarchy. Furthermore, we show that any randomized hierarchical cooperative caching algorithm with capacity blowup b has competitive ratio Ω(log d b ) against an oblivious adversary. Thus we establish that there is no resource competitive algorithm for the hierarchical cooperative caching problem. Second, we address a class of compression caching problems in which a file can be cached in multiple formats with varying sizes and encode/decode costs. In this work, we address three problems in this class of compression caching. The first problem assumes that the encode cost and decode cost associated with any format of a file are equal. For this problem we present a resource competitive online algorithm. To explore the existence of resource competitive online algorithms for compression caching with arbitrary encode costs and decode costs, we address two other natural problems in the aforementioned class, and for each of these problems, we show that there exists a non-constant lower bound on the competitive ratio of any online algorithm, even if the algorithm is given an arbitrary factor capacity blowup. Thus, we establish that there is no resource competitive algorithm for compression caching in its full generality. Third, we address the problem of aggregation over trees with the goal of adapting aggregation aggressiveness. Consider a distributed network with nodes arranged in a tree, and each node having a local value. We consider the problem of aggregating values (e.g., summing values) from all nodes to the requesting nodes in the presence of writes. The goal is to minimize the total number of messages exchanged. The key challenges are to define a noix tion of “acceptable” aggregate values, and to design algorithms with good performance that are guaranteed to produce such values. We formalize the acceptability of aggregate values in terms of certain consistency guarantees. We propose a lease-based aggregation mechanism, and evaluate algorithms based on this mechanism in terms of consistency and performance. With regard to consistency, we adapt the definitions of strict and causal consistency to apply to the aggregation problem. We show that any lease-based aggregation algorithm provides strict consistency in sequential executions, and causal consistency in concurrent executions. With regard to performance, we propose an online lease-based aggregation algorithm, and show that, for sequential executions, the algorithm is constant competitive against any offline algorithm that provides strict consistency. Our online lease-based aggregation algorithm is presented in the form of a fully distributed protocol, and the aforementioned consistency and performance results are formally established with respect to this protocol. We also present experimental results to show that the algorithm performs well under various workloads.Item Architectures and algorithms for high performance switching(2004) Prakash, Amit; Aziz, AdnanSwitches are ubiquitous in modern computing, appearing in wide-area networks, multiprocessor servers, and data storage systems. With the the advent of high-speed link technology, switches have become the bottleneck in moving data in the network. Existing switch architectures either require the interconnection network and packet buffers to work at a very high speed or require complex scheduling problems to be solved quickly. In this dissertation we investigate whether there are switch architectures that can support high-speed links that are simultaneously easy to schedule, and can be built out of inexpensive components. The approach we take is using parallelism to solve complex scheduling problems. We choose switching architectures such that the corresponding scheduling problem can be efficiently solved with a reasonable amount of hardware. In particular, we present two switch architectures for which we have developed efficient scheduling algorithms. The first switch achieves optimum throughput and optimum average latency while the second switch guarantees optimum throughput only but uses considerably less hardware.Item Computer mediated communications: an analysis of three mass communications mailing lists(Texas Tech University, 1955-01) Triplett, Timothy LorenNot availableItem Cross-layer discovery and routing in mobile ad-hoc networks(2006-05) Venkataraman, Meenakshi; Julien, ChristineCommunication in ad hoc networks traditionally relies on network addresses known a priori. This work addresses the need for application-aware adaptive communication that creates network routes based on applications’ dynamic resource requests. We motivate this need by examining the state of the art in mobile ad hoc network communication, the requirements of applications, and the impact of existing protocols on flexibility and efficiency. We introduce an intuitive generalization to source routing which facilitates discovery of a resource in an ad hoc network and the creation and maintenance of a route from the requesting host to the discovered destination. We thus eliminate the requirement that existing routing protocols be coupled with a name or resource resolution protocol, instead favoring an entirely reactive approach to accommodate significant degrees of mobility and uncertainty. We present an initial implementation, a performance evaluation, and a comparison to existing alternatives.Item Data reduction algorithms for distributed query processing(Texas Tech University, 1984-08) Wang, Jia-shinnNot availableItem Design of a P2P-based network architecture for automated test equipment(Texas Tech University, 2004-05) Pandit, ParagSchemes that use intercormected devices such as control systems and Automated Test Equipment (ATE) traditionally use software that is built upon the client-server model. As a result, these systems are incapable of guaranteeing control of the master over slaves in the event of many cases of system failure. Also, these systems are often written in compiled languages like 'C' or 'Assembly', which makes the task of recompiling software and rebooting systems necessary when modifications are performed. In an effort to provide greater fault tolerance and reliability, we explore the possibility of using the P2P model for networking devices. Moreover, we attempt to use scripts for defíning system behavior, which provides flexibility and ease in making modifications at runtime. We met our goal by developing a distributed P2P architecture for confederations of devices and by defíning an XML-based scripting language for writing distributed applications that run on the said platform. Message protocols for communication between devices were defíned. Many useful features were implemented that make the framework powerfiil and yet simple to use.Item Distributed program reliability based on minimum file spanning trees(Texas Tech University, 2000-12) Krishnan, KirtiThe objective of this thesis was to develop a generalized modeling technique using Petri Nets based on Minimum File Sparming trees and to generate reliability measures for a distributed program in the given distributed computing environment. A global repair state was also incorporated into the final model to measure the availability of the program. (The idea proposed features the concept of using Minimum File Spanning trees as the major component in the Petri Net model rather than the individual components of the system, thereby achieving a reduction in the state space and improved efficiency in the generation of reliability results.Item Examination of web page interests and computer skills of members of a professional association(Texas Tech University, 2002-05) Marquez-Hall, SandraThe purpose of this study was to survey the membership of the Education and Technology (E&T) Division of the American Association of Family and Consumer Sciences (AAFCS) to contribute, in part, to the development of the technology strategic plan for building the E&T Division web page. The profession is recognized as an integrative field of study focused on the well being of individuals, families, and consumers and the reciprocal relations with their environments. Classifications within the AAFCS membership are by divisions, to indicate the member education emphasis, and, sections to represent member employment areas. Eight objectives were established to guide the study. The objectives for the survey focused on the following areas; current visitation to the AAFCS Web Site, interest in four topics and 23 sub-topics to be included at the website, intent to use five communications utilities, level of need for seven website features, current computer use, websites visited most often in professional role, frequency of use of the computer for seven processes, seven computer-related training needs, how decisions should be made about what is included at the web page, and the professional background of respondents. The sample for the research study was drawn from the 1999 membership list of the E&T Division supplied by the headquarters office of the American Association of Family and Consumer Sciences. At the time, there were approximately 3,800 registered members in the E&T Division. A 20% random sample, crossed by each of the six sections of the Association represented within the division was selected. A finding of the study was the disparity in the number of members in the individual sections of the association; eighty-five percent of the division members were in the Elementary, Secondary and Adult Education Sections. Therefore, the sample was combined for data analysis. Using a researcher-developed instrument, the traditional mail survey was sent out in May 1999. An online version of the survey was published on the World Wide Web (WWW) in May 2000. The combined responses to the two surveys (N=371) resulted in a 24% overall return. The surveys generated both qualitative and quantitative data with regard to the questions asked. American Association of Family and Consumer Sciences Education and Technology Division members responding to the survey were seasoned educators who were employed in the public school system at the secondary level (64%), the college level (12%), and other positions in the public domain. Members of the E&T Division were looking for practical support for their professional roles. Respondents expressed the highest level of interest for teaching materials and teaching-related information, web sites, and advertisement/online exhibits. There were also high levels of interest in distant education courses, curriculum center links, factual information and critical issues, public affairs/legislation, and a membership directory. Member interest in web site features and communication utilities indicated the highest intent to use electronic mail, links, and networking opportunities. Computer literate, the respondents used E-mail, the Internet, and WWW frequently. The division members wanted training in web page development and applications for integration of the computer into the classroom. Members wanted a recognized authority familiar with the professions interests, making decisions about what is to be accepted at the web page. This study was one portion of a larger effort toward developing a technology strategic plan for the E&T Division. Considerations outside of the parameters of this project such as the ability of the AAFCS organization to implement changes, and to provide staffing to support the recommendations for the E&T Division web pages were unknown.Item Flow decomposition of cost-constrained networks(2007-12) Bodas, Shreeshankar Ravishankar; Vishwanath, SriramIn this thesis, we consider the problem of communicating data over a network of cost-constrained networks. We first look at a network with a single source and a single destination and prove that the information-theoretic cut-set outer bound matches the ow min-cut bound if the network has mutually independent, memoryless links. We then impose the cost constraint on the links and the overall network and prove that the aforementioned two bounds match in the limit as the packet size tends to infinity. We also provide transmission schemes that achieve the outer bounds, proving that these bounds actually equal the capacity of the network under the cost constraints. Finally, we consider a multi-source, multi-destination network of cost-constrained links and show that the information theoretic cut-set outer bound matches the ow outer bound, when the network is comprised of mutually independent, memoryless links.Item A fractional N frequency synthesizer for an adaptive network backplane serial communication system(2005) Rangan, Giri N. K.; Swartzlander, Earl E.An architecture and design of a Phase Locked Loop based frequency synthesizer is developed in this dissertation. Using multiple phases generated by a ring oscillator, this synthesizer is able to generate non-integer multiples of the incoming, high quality clock signal. The design is done for a nominal target frequency of 3.125 GHz for application in a serial communication system such as a network backplane. Using a fully differential design, the architecture is able to achieve the stringent timing jitter requirements of a network backplane system. Advancements in the content and the coverage of the Internet have tremendously increased the need for high speed data transport over very long and very short distances. The long distance bandwidth and speed requirements have been addressed by the use of optical links. The shorter distances, such as serial communications in a network backplane are still in the realm of copper lines drawn on printed circuit boards. Thus the medium of communication places design constraints on the electronic devices operating on either side of the medium. As symbol frequencies approach 3.125 GHz and beyond, architectural modifications must be made to alleviate the channel effects. This dissertation presents a phase locked loop for a network backplane system application where the two transceivers can communicate with each other to determine a particular line code that they will use for the most optimal communication between them. The selection of the line code determines the symbol rate and in turn the transmit clock frequency. A particular line code may be chosen such that a non-integer multiple of a low frequency input clock is required. The incoming clock is usually fixed at standard frequencies like 312.5 or 625 MHz to operate the parallel data path. It would then be beneficial to have a fractional-N frequency synthesizer which can generate the necessary fractional frequency multiples. The synthesizer presented in this research work is designed in a standard 0.13 µm CMOS technology with a 1.5 V power supply. It dissipates 112 mW of power and occupies an estimated silicon area of 0.2 sq. mm. The nominal peak to peak jitter of this design is approximately 43.7 ps and the maximum peak to peak jitter is 48 ps.Item From paper to digitized expression: a treatment of intellectual property issues in application to rhetoric and technical communication(Texas Tech University, 1997-05) Herrington, Tyanna K.Although the topic of intellectual property law is virtually absent from the range of scholarship in the field of rhetoric and technical communication, because control of intellectual property is tantamount to control of knowledge creation, it is an area of grave importance to participants in the field. This dissertation examines the intersection among rhetoric and technical communication, the Internet, and intellectual property law. The study consists of two parts: the first is a pragmatic approach to understanding and applying the existing law; the second is a theoretical examination of the effect of the differing ideological stances on interpretation of intellectual property law. It also focuses directly on the effects of digitized communication and the impact of the Internet community on interpretations of the concepts of "authorship," "ownership," and "property." The study reveals that the ideological differences between the communities of rhetoric and technical communication and the Internet, and that of the legal community derive differing interpretations of "authorship," "ownership," and "property." The dissertation concludes by arguing that to follow the dominant ideological stance of the legal community can lead to a definition of property that subverts the intent of the constitutional intellectual property statute and, in turn, effectively prohibits egalitarian access to the dialogic process of knowledge creation that supports the cultural development of society.Item High-speed optical networking with ethernet(Texas Tech University, 2000-05) Patwardhan, ShriramThe main focus of this thesis is establishing high-speed connectivity of workstations over optical fiber. The networking of these workstations is carried out by transmission of'Fast Ethernet' data at 100 Mbps. There are commercially available fiber transceivers that provide high fi-equency Ethernet connectivity at 100 Mbps, but this is discouraging from the viewpoint of the very high costs involved. The research carried out towards this thesis promises not only a technically workable high-speed fiber optic communications network but also an economically viable solution that can be implemented over the entire university campus. The lasers and photoreceivers used in the experiments are capable of handling very high frequency digital signals. This assures reliability of the fiber network at very high speeds. A design to implement the networking of eight departments of the university using WDM(Wavelength Division Multiplexing) is discussed. This is supported by a mathematical model that simulates the performance of the network in terms of delay and throughput. Further experiments have been performed to achieve a four-wavelength WDM network over 6.2 km of single mode fiber at a data rate of 2.5 Gb/s. This simulates high-speed Ethernet fiber optic transmission at 2.5 Gb/s which is an OC-48 SONET standard.Item Implementation and utilization of a heterogeneous multicomputer cluster for the study of load balancing strategies(Texas Tech University, 1997-08) Andersen, Per H.Not availableItem Implementation of a network file transfer using TOP specifications(Texas Tech University, 1988-05) Ravikumar, ChakravarthiNOT AVAILABLEItem Improving performance and incentives in disruption-tolerant networks(2010-08) Shevade, Upendra; Zhang, Yin, doctor of computer science; Browne, James; Mok, Aloysius; Qiu, Lili; Vin, HarrickThe recent proliferation of personal wireless devices has led to the emergence of disruption-tolerant networks (DTNs), which are characterized by intermittent connectivity among some or all participating nodes and a consequent lack of contemporaneous end-to-end paths between the source and consumer of information. However, the success of DTNs as a communication paradigm is critically dependent on the following challenges being addressed: (1) How to enable popular but demanding applications, such as video-on-demand, to operate in such constrained network settings, and (2) How to incentivize individual devices to cooperate when network operation is only possible under, or greatly benefits from cooperation. In this dissertation, we present a novel set of protocols and develop real systems that effectively meet the above challenges. We make the following contributions: First, we design and implement a novel system for enabling high bandwidth content distribution in vehicular DTNs by leveraging infrastructure access points (APs). We predict which APs will soon be visited by a vehicular node and then proactively push content-of-interest to those APs. Our replication schemes optimize content delivery by exploiting Internet connectivity, local wireless connectivity, node relay connectivity and mesh connectivity among APs. We demonstrate the effectiveness of our system through trace-driven simulation and Emulab emulation using real taxi and bus traces. We further deploy our system in two vehicular networks: a fourteen AP 802.11b network and a four AP 802.11n network with smartphones and laptops as clients. Second, we propose an incentive-aware routing protocol for DTNs. In DTNs, routing takes place in a store-and-forward fashion with the help of relay nodes. If the nodes in a DTN are controlled by rational entities, such as people or organizations, the nodes can be expected to behave selfishly by attempting to maximize their utilities and conserve their resources. Since routing is inherently a cooperative activity, system operation will be critically impaired unless cooperation is incentivized. We propose the use of pair-wise tit-for-tat (TFT) as a simple, robust and practical incentive mechanism for DTNs. We then develop an incentive-aware routing protocol that allows selfish nodes to maximize their own performance while conforming to TFT constraints.Item Network congestion control(2001-08) Yang, Yang; Lam, Simon S., 1947-In a shared network such as the Internet, end systems should react to congestion by adapting their transmission rates to avoid congestion collapse and to keep network utilization high. The robustness of the current Internet is due in large part to the end-to-end congestion control mechanisms of TCP. Although TCP congestion control is appropriate for applications such as bulk data transfers, many new applications would find TCP’s behavior of halving the sending rate of a flow to be too severe a response to a single congestion indication, as it can noticeably reduce the flow’s user-perceived quality. However, since the dominant Internet traffic is TCP-based, it is important that new congestion control schemes be TCP-friendly. By this, we mean that the sending rate of a non-TCP flow should be approximately the same as that of a TCP flow under the same conditions of round-trip time and packet loss. The first problem I investigate is a more general version of AIMD (GAIMD) than what is implemented in TCP; specifically, the sender’s window size is increased by alpha if there is no packet loss in a round-trip time, and the window size is decreased to beta of the current value if there is a triple-duplicate loss indication, where alpha and beta are parameters. Using the relationship between the sending rate of GAIMD and the two parameters, I derive a simple relationship between alpha and beta for a GAIMD flow to be TCP-friendly. This relationship offers a wide selection of possible values for alpha and beta to achieve desired transient behaviors. I then investigate the fairness, smoothness, responsiveness, and aggressiveness of TCP, GAIMD and two other representative TCP-friendly congestion control protocols. The properties of these protocols are evaluated both analytically and via simulation by studying their responses to three network changes. Considering the inherent fluctuations in a stationary network environment, I define three types of sending rate variations, and derive an analytical expression for the CoV for each of the four protocols. I also study protocol responsiveness and aggressiveness by evaluating their responses to a step increase of network congestion and a step increase of available bandwidth. The third problem I investigate is the congestion control issues in multicast environments. A multicast session may have a large number of receivers with heterogeneous reception capacities determined by the fairness requirement of a network or by device capacity. To accommodate this heterogeneity, various multi-rate schemes, based upon the use of layering or replication, have been proposed. For a general class of receiver utility functions, I show that there exists an optimal partition that is ordered, which gives rise to efficient algorithms to find an optimal partition based upon dynamic programming. I also show algorithms to efficiently determine the optimal sending rate of each partitioned group. Furthermore, for several typical distributions of receivers’ capacities, I show that the majority of the benefit of a multi-rate scheme can be gained by using a small number of layers (or groups).Item Network-on-chip implementation and performance improvement through workload characterization and congestion awareness(2008-12) Gratz, Paul V., 1970-; Keckler, Stephen W.Off-chip interconnection networks provide for communication between processors and components within computer systems. Semiconductor process technology trends have led to the inclusion of multiple processors and components onto a single chip and recently research has focused on interconnection networks, on-chip, to connect them together. On-chip networks provide a scalable, high-bandwidth interconnect, integrated tightly with the microarchitecture to achieve high performance. On-chip networks present several new challenges, different from off-chip networks, including tighter constraints in power, area and end-to-end latency. In this dissertation, I propose interconnection network architectures that address the unique design challenges of power and end-to-end latency on chip. My work in the design, implementation and evaluation of the on-chip networks of the TRIPS project’s prototype processor, a real hardware implementation, is the foundation for my work in on-chip networking. Based on my analysis of the TRIPS on-chip networks and their workloads, I propose, design, and evaluate novel network architectures for congestion monitoring and adaptive routing that are matched to the design constraints of on-chip networks. In the TRIPS system we designed, and implemented in silicon, a distributed processor microarchitecture where traditional processor components are divided into a collection of self-contained tiles. One novel aspect of the TRIPS system is the control and data networks that the tiles use to communicate with one another. I worked on the design and implementation of one of these networks, the On-Chip Network (OCN). The OCN, a 4x10 mesh network, interconnects the tiles of the L2 cache, the two processor cores and various I/O units. Another on-chip network, the Operand Network (OPN), interconnects the execution units and serves as a bypass network, integrated tightly with the processor core. In this document I evaluate these two on-chip networks and their workloads, these evaluations serve as case studies in how on-chip design constraints affect the design of on-chip networks. In the examination of the TRIPS OCN and OPN networks, one insight we gained was that network resource imbalances can lead to congestion and poor performance. We found these imbalances are transient with time and task. Timely information about the status of the network can be used to balance the resource utilization, or reduce power. A challenge lies in providing the right information, conveyed in a timely fashion, as the metrics and methods used in off-chip networks do not map well to on-chip networks. In this document, I propose and evaluate several metrics of network congestion for their utility and feasibility in an on-chip environment. In our examination of the TRIPS on-chip networks we also found that minimizing end-to-end packet latency was critical to maintaining good system performance. Effective use of the congestion information without impact to end-to-end latency is another challenge in on-chip networking. I explore novel adaptive routing techniques that address the challenge of managing the end-to-end latency. A method that produces good results is aggregation of network status information, reducing both the bandwidth and latency required for status information transmission. In this dissertation I examine how well this technique and others compare with conventional oblivious and adaptive routing.Item Retrospect on contemporary Internet organization and its challenges in the future(2011-05) Gutierrez De Lara, Felipe; Bard, William Carl, 1944-; Julien, ChristineThe intent of this report is to expose the audience to the contemporary organization of the Internet and to highlight the challenges it has to deal with in the future as well as the current efforts being made to overcome such threats. This report aims to build a frame of reference for how the Internet is currently structured and how the different layers interact together to make it possible for the Internet to exist as we know it. Additionally, the report explores the challenges the current Internet architecture design is facing, the reasons why these challenges are arising, and the multiple efforts taking place to keep the Internet working. In order to reach these objectives I visited multiple sites of organizations whose only reason for existence is to support the Internet and keep it functioning. The approach used to write this report was to research the topic by accessing multiple technical papers extracted from the IEEE database and network conferences reviews and to analyze and expose their findings. This report utilizes this vii information to elaborate on how network engineers are handling the challenges of keeping the Internet functional while supporting dynamic requirements. This report exposes the challenges the Internet is facing with scalability, the existence of debugging tools, security, mobility, reliability, and quality of service. It is explained in brief how each of these challenges are affecting the Internet and the strategies in place to vanquish them. The final objectives are to inform the reader of how the Internet is working with a set of ever changing and growing requirements, give an overview of the multiple institutions dedicated to reinforcing the Internet and provide a list of current challenges and the actions being taken to overcome them.