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ABSTRACT During recent years, the trends in computer resource organization have seen the replacement of the traditional mainframe computers and their timesharing terminals with individual desktop workstations. These workstations can offer more computational power than the mainframes of less than a decade ago. With this distribution of processing from the more traditional mainframe computer comes the need to share peripheral resources among these desktop workstations. These include items such as file systems, tape drives, printers, plotters, and graphics display devices. A common way to share these among the multi-computer environment is to provide a transparent gateway that allows each workstation to function as if it had a dedicated set of peripherals. As educational institutions and industry continue the trend of connecting their computer systems in networks, a serious hole has developed - the ability to estimate the throughput of their network. This paper describes the development, use, and verification of the Local Area Network Simulation Package (LANSIM). LANSIM provides a means to determine the performance characteristics of any network adhering to the ANSI/IEEE Std 802.3-1985 for local area networks. This will allow anyone to simulate a proposed network and gain insight into such crucial topics as percent utilization, aggregate data rates on the network, and response times - all prior to the purchase and installation of the network.

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Yes / With the rapid growth of security threats in computer networks, the need for developing efficient security‐warning systems is substantially increasing. Distributed denial‐of‐service (DDoS) and DoS attacks are still among the most effective and dreadful attacks that require robust detection. In this work, we propose a new method to detect TCP DoS/DDoS attacks. Since analyzing network traffic is a promising approach, our proposed method utilizes network traffic by decomposing the TCP traffic into control and data planes and exploiting the dynamic time warping (DTW) algorithm for aligning these two planes with respect to the minimum Euclidean distance. By demonstrating that the distance between the control and data planes is considerably small for benign traffic, we exploit this characteristic for detecting attacks as outliers. An adaptive thresholding scheme is implemented by adjusting the value of the threshold in accordance with the local statistics of the median absolute deviation (MAD) of the distances between the two planes. We demonstrate the efficacy of the proposed method for detecting DoS/DDoS attacks by analyzing traffic data obtained from publicly available datasets. / The Deanship of Scientific Research, King Saud University. The Gulf Science, Innovation, and Knowledge Economy Programme of the U.K. Government

In this thesis, the design and performance issues of a protocol for a dynamic hierarchical local area network are addressed. The dynamic hierarchy is an extension of the static hierarchical topology with the exception that the apex node can vary among a prescribed set of candidates. A simulation model is used to evaluate the benefits of dynamic apex transition under the proposed protocol. The design also considers routing and queue structures of the nodal functions corresponding to the transport/network layers of the ISO model. The model experimentation shows that dynamic hierarchy networks are advantageous, under an environment where different network traffic patterns exist at different points of time, over static hierarchy networks. Critical to the conclusion is that the amount of time taken to effect a transition is kept minimal. / M.S.

Network management and control of large broadband local area networks, where the number of nodes ranges from several hundred to a few thousand, is a very important concern for today's network manager. This primarily involves tuning the network to ensure load balance over the broadband subchannels, and the capability to monitor specific nodes for accounting, performance and security purposes. This thesis presents the design considerations for a session level passive hardware monitor on a broadband local area network having a bus/tree topology. A methodology for session monitoring is presented based on the issues discussed. The session service provided is packet switched with point to point virtual circuit connection. Current technology and economics dictate the use of broadband transmission media for large local area networks spread out over a radius of around ten kilometers. This medium provides adequate throughput for a large number of devices by supporting frequency division multiplexing and a multiple access medium access control protocol. The design considerations include both hardware and software aspects and are justified based on the characteristics of the transmission medium and communication protocol architecture used in this study. The local area network used for the development of this project is a sixteen hundred node campus network at Virginia Tech (™LocalNet 20) supplied by SYTEK, Inc. / M.S.

This dissertation studied cognitive packet networks (CPN) which build networked learning systems that support adaptive, quality of service-driven routing of packets in wired networks and in wireless, mobile ad hoc networks. The first part of this study completed the design of the CPN algorithm for wired systems by revisiting the decision making procedure employed by smart packets in the former initiative. To conduct evaluation studies, this work proposed two implementation architectures, both of which were integrated into the Linus 2.4 kernel. The second part of this dissertation extended CPN to ad hoc networks by introducing mechanisms to handle node mobility with a new quality-of-service metric that makes better use of the limited resources typically present in such networks. in ad hoc CPN (AHCPN), path availability quantifies a path via the probability to find nodes and links available for routing; it is defined as a function of battery lifetime at nodes and signal-to-noise ratio of communication channels. As a result, nodes which have low power are able to extend their working lifetime and routes are selected based on power considerations, leading to the establishment of more robust communication paths over time. This research included the deployment of three network testbeds and extensive experimentation to verify the performance of both CPN and AHCPN. In addition, a simulation model of ACHPN was developed using Network Simulator 2 (NS-2). Measurements on real systems and simulations revealed great capacity for adaptability and successful performance of both CPN and AHCPN under different network conditions.

With multimedia communication growing in popularity, it has become important to develop techniques that will allow a multimedia application to access multimedia files from local as well as remote sites. This thesis describes the methodology used in the design of the Network Multimedia File System (NMFS) protocol. The protocol provides “transparent access to shared files across networks” much like Sun’s Network File System (NFS) protocol. However, NMFS differs from NFS in that it provides a connection-oriented service that allows the user to specify quality of service (QOS) parameters and reserve resources to achieve the desired QOS. NMFS is an application layer protocol and is intended to work with existing multimedia applications, unaltered, on multiple platforms. NMFS will provide real-time delivery of multimedia data over networks both designed and not designed to carry multimedia traffic. A unique feature of this protocol is that it uses an anticipated delivery schedule (ADS) to guide prefetch of portions of files that are likely to be requested in the future. This prefetched data is stored in a local buffer which reduces the need to transfer the data over the variable latency network when the application actually requests it. Thus NMFS provides most unaltered application programs with almost constant latency accesses over a network with variable latency. / Master of Science

The research described in this thesis deals with effective protocol specification. The primary question addressed is whether the Express Transfer Protocol (XTP), a "real-time" Transport layer protocol, is sufficiently specified or are there "holes" in its specification? A new protocol evaluation process is formulated and applied to XTP in order to answer this question. The evaluation process combines a detailed analysis of the XTP specification with an attempt to implement parts of the protocol from the specification. Special attention is given to those aspects of the protocol that affect "real-time" naval tactical communications. The detailed analysis of the specification and its effect on the specification revision process are presented. The analysis is described in formal comment papers and electronic mail transmitted to the protocol designer, Dr. Greg Chesson. Elements of the protocol most applicable to tactical communication are selected for implementation. A number of assumptions are made so that an implementation can be built. The design of the prototype implementation and the assumptions made to build it are discussed. Both the hardware and software being used to build the implementation are presented. The protocol evaluation process is found to be appropriate for evaluating XTP. A comparison is made between this technique of protocol evaluation and existing techniques (i.e., simulation, complete implementation, and protocol verification). The principal conclusion of the protocol valuation process is that a number of areas of the XTP Protocol Definition (prior to Revision 3.3) are not sufficiently specified. These areas must be properly specified before a complete implementation can be built. Without a complete specification, the communications support intended for XTP is unlikely to be realized. / Master of Science