Modeling and performance analysis of ATM LANs

Asynchronous Transfer Mode (ATM} is a method of data transmission using small fixed-length cells. This thesis presents a model of an ATM LAN which provides a realistic representation of data transmission over the system by explicitly modeling both the ATM network and the applications running over that network. Coloured timed Petri nets are used to create a compact model that is capable of representing a variety of different protocols at a high level of detail. The model is designed to allow easy reconfiguration or addition of detail at different levels of the system. Simulation is used to evaluate the performance of the model, and results are compared to actual data gathered from the Memorial University campus network

CFTP: a caching FTP server

By analyzing the log files generated by the UK National Web Cache and by a number of origin FTP sites we provide evidence that an FTP proxy cache with knowledge of local (national) mirror sites could significantly reduce the amount of data that needs to be transferred across already overused networks. We then describe the design and implementation of CFTP, a caching FTP server, and report on its usage over the first 10 months of its deployment. Finally we discuss a number of ways in which the software could be further enhanced to improve both its efficiency and its usability

Storing and managing data in a distributed hash table

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 83-90).Distributed hash tables (DHTs) have been proposed as a generic, robust storage infrastructure for simplifying the construction of large-scale, wide-area applications. For example, UsenetDHT is a new design for Usenet News developed in this thesis that uses a DHT to cooperatively deliver Usenet articles: the DHT allows a set of N hosts to share storage of Usenet articles, reducing their combined storage requirements by a factor of O(N). Usenet generates a continuous stream of writes that exceeds 1 Tbyte/day in volume, comprising over ten million writes. Supporting this and the associated read workload requires a DHT engineered for durability and efficiency. Recovering from network and machine failures efficiently poses a challenge for DHT replication maintenance algorithms that provide durability. To avoid losing the last replica, replica maintenance must create additional replicas when failures are detected. However, creating replicas after every failure stresses network and storage resources unnecessarily. Tracking the location of every replica of every object would allow a replica maintenance algorithm to create replicas only when necessary, but when storing terabytes of data, such tracking is difficult to perform accurately and efficiently. This thesis describes a new algorithm, Passing Tone, that maintains durability efficiently, in a completely decentralized manner, despite transient and permanent failures. Passing Tone nodes make replication decisions with just basic DHT routing state, without maintaining state about the number or location of extant replicas and without responding to every transient failure with a new replica. Passing Tone is implemented in a revised version of DHash, optimized for both disk and network performance.(cont.) A sample 12 node deployment of Passing Tone and UsenetDHT supports a partial Usenet feed of 2.5 Mbyte/s (processing over 80 Tbyte of data per year), while providing 30 Mbyte/s of read throughput, limited currently by disk seeks. This deployment is the first public DHT to store terabytes of data. These results indicate that DHT-based designs can successfully simplify the construction of large-scale, wide-area systems.by Emil Sit.Ph.D

Програмне забезпечення: практикум з англійської мови для студентів фізико-математичного факультету спеціальностей: «Інформатика», «Математика та інформатика», «Фізика та інформатика»

Практикум складається з 8 розділів, текстів для самостійного опрацювання, додаткового читання та додатків. Тексти підібрані з оригінальної науково-технічної літератури та містять необхідну термінологію зі спеціальності. До складу розділів входять вправи на закріплення лексико-граматичного матеріалу, тести, запитання. Вправи та тести побудовано на мовному матеріалі, який використовується в текстах розділів. Додається підсумковий тест для перевірки знань всього курсу. Для студентів неспеціальних факультетів денної, заочної та дистанційної форми навчання, які вивчають інформатику. Пізнавальний характер текстів зацікавить не лише зазначене коло студентів, але й усіх тих, хто поглиблено вивчає англійську мову

Multi-Media Mail in heterogeneous Networks

The MIME approach seems to be the most reasonable effort for allowing the sending and receiving of multimedia messages using standard Internet mail transport facilities. Providing new header fields, such as MIME-Version, Content-Type, and Content- Transfer-Encoding, it is now possible to include various kinds of information types, e.g. audio, images, richtext, or video, into a RFC 822-conformant mail. Making use of these headers, it is possible to fully describe an attached body part, so that a receiving mail user agent is able to display it without any loss of information. Additionally, the definition of the "multipart" and "message" content types allows the creation of hierarchical structured mails, e.g. a message containing two alternative parts of information, one that can be shown using a simple ASCII-terminal, the other to be displayed on a multimedia workstation. Allowing the definition of bilaterally defined content types and providing a standardized means of establishing new content types prevent MIME from being a one-way road and supply mechanisms to extend MIME for future use

Small Business Information Security

Small businesses account for over fifty percent of the Gross National Product of the U.S. economy; and the security of their information systems is critical for them to operate, compete, and remain profitable. While many security studies have been conducted and reported on enterprise scale organizations, similar research on small businesses in the U.S. is limited. One small business was evaluated by an information security audit to determine if its information resources and network were adequately secure, and will be used as a test case to identify an approach a typical small business may take to secure their networks and data to avoid unnecessary liability exposure. By examining the specific risk factors in this case study, the author believes parallels can be drawn by other small businesses as a starting point for examining their own risk factors. Additionally this study provides a series of proposed mitigation processes to improve the small businesses' network security that can be adopted by other small businesses in like circumstances. The mitigation processes are specifically tailored to the small business industry itself, as opposed to a larger organization that has a greater exposure to risk vulnerability and that also has larger asset pools from which to secure their networks.   The method utilized for this research was qualitative in nature, using a form of Participatory Action Research (PAR). This approach was most appropriate in that it allows the researcher to act in partnership with the small business to attempt to affect social change that will help in securing the small business's information resources. An information security audit was performed on a small business to identify actual and potential threats, and an electronic questionnaire was distributed to the employees to gauge their individual perspectives of the clarity and comprehensibility of the business's security policy, the consequences of violations to the company's policy, how well the company's policy is disseminated and tracked for compliance, and if they have knowledge of steps to be taken in response to an incident or disaster. There were four objectives of this study. The first objective was to evaluate a small business's information security posture. The second objective was to determine if the small business had experienced any information technology security incidents. The third objective was to evaluate whether the incidents were caused by a lack of a policy, standard or procedure; an ineffective policy, standard or procedure; a lack of training and education; or a reluctance to enforce or monitor adherence to established policy, standards, or procedures. And the fourth objective was to recommend to the small business any changes or additions that would reduce the small business's exposure to information security threats, risks and vulnerabilities through effective information security risk management.  M.S

Bandwidth management and monitoring for IP network traffic : an investigation

Bandwidth management is a topic which is often discussed, but on which relatively little work has been done with regard to compiling a comprehensive set of techniques and methods for managing traffic on a network. What work has been done has concentrated on higher end networks, rather than the low bandwidth links which are commonly available in South Africa and other areas outside the United States. With more organisations increasingly making use of the Internet on a daily basis, the demand for bandwidth is outstripping the ability of providers to upgrade their infrastructure. This resource is therefore in need of management. In addition, for Internet access to become economically viable for widespread use by schools, NGOs and other academic institutions, the associated costs need to be controlled. Bandwidth management not only impacts on direct cost control, but encompasses the process of engineering a network and network resources in order to ensure the provision of as optimal a service as possible. Included in this is the provision of user education. Software has been developed for the implementation of traffic quotas, dynamic firewalling and visualisation. The research investigates various methods for monitoring and management of IP traffic with particular applicability to low bandwidth links. Several forms of visualisation for the analysis of historical and near-realtime traffic data are also discussed, including the use of three-dimensional landscapes. A number of bandwidth management practices are proposed, and the advantages of their combination, and complementary use are highlighted. By implementing these suggested policies, a holistic approach can be taken to the issue of bandwidth management on Internet links

WEBassess

This project and research has resulted in the development of a World Wide Web (WWW) based testing system. WEBassess can be accessed and used from any point in the world that has a connection to the WWW. The WEBassess system allows for the creation and completion of tests through the WWW interface. Scoring and feedback of submitted tests is completely automated, allowing students to see their test result immediately, including visual indicators for correct and incorrect answers. These test results may then be viewed by academic staff, showing complete test details, such as unit code, test title, score, percentage, date and time of test submission plus correct and incorrect answers. Through the logging of this information into the WEBassess database, profiles can be derived, indicating which students are having the most difficulty with certain questions. This information is stated against a student\u27s identification number. The entire WEBassess system can be administered through a consistent WWW interface, including the addition, deletion and maintenance of pools of questions. User maintenance is also included in this administration module, allowing for the addition, deleting and alteration of Admin, Staff and Student level users. Security is implemented in the form of passwords linked to specific user identification details. A WEBassess user is presented with only the screens which their level of access allows, be it Administration (Admin), Staff or Student. The WEBassess system has been developed using a variety of software and hardware tools, the most crucial of these being an application called Lasso (Blueworld Inc, 1997) and the Filemaker Pro 3 (Claris Corporation, 1997) relational database. The Lasso application communicates with the Filemaker Pro database via a WWW server. The WEBassess system has been designed as a tool for student knowledge testing and feedback, rather than as a traditional assessment and scoring device. Features found in the WEBassess system have been created to comply with specific requirements for Edith Cowan University staff and students, whilst other features have been derived from similar testing systems currently in use on the WWW. The WEBassess system is presently at the level of preliminary user testing, from which initial changes to the system have already taken place. Several future developments for the system are envisaged, to be implemented after a prolonged period of end-user testing on the finalised program

CPA WebTrust practitioners\u27 guide

https://egrove.olemiss.edu/aicpa_guides/1788/thumbnail.jp