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No description available.

Resource Management is an extremely important concern for the network manager. Of the bus, ring and the star network topologies, usually employed in a local area network, the bus topology provides the highest reliability. However, peer-to-peer protocols usually followed in such a topology, make it extremely difficult to incorporate resource management features at a lower level of network architecture. This thesis presents design considerations for a session-level network controller, to be implemented on a local area network with a bus topology. The controller, will provide essential resource management, and attempt to improve the throughput of the network. The design is based on a single-board computer, and a streamlined operating system is also included in the design. It is claimed that such an environment will be ideal for networking tasks, like the controller presented. The design is software-oriented, though device selection is discussed, both for the controller and its network interface. The local area network used for the development of this project is a sixteen hundred node campus network at Virginia Tech ( using LocalNet 20) supplied by SYTEK, Inc. / M.S.

The token ring has several advantages over other networks, especially under a heavy load. However, Bux and Grillo showed that all desirable characteristics of IEEE 802.2 and 802.5 protocols for a single token ring are severely degraded in an interconnected token ring network. In order to address the problem, Bux and Grillo suggested a method of dynamically adjusting the size of windows depending on the traffic of a network. In this thesis, a different method of addressing the problem was proposed. The proposed method is to add a secondary transmission link to the backbone ring of a network to form a double linked backbone ring network. Simulation results show that the most influential element contributing to the degradation of performance is congestion at the bridges in a network. The processing speed of bridges for the proposed double linked backbone ring network is essentially double that of the original network. The increased processing speed of the bridges enhances the performance of the network. Experimental results for the utilization, throughput and response time of the original network and the proposed double linked backbone ring are presented: / Master of Science

This research investigates various aspects of user-perceived network performance over a local area network for two transport layer protocols: TCP and UDP. The sensitivity of user-level performance to the choice of different speed hosts, host loads, and application program interfaces are studied. Our measurements serve as a guide in designing performance critical applications. Moreover, we present a detailed timing analysis of the dynamic behavior of the TCP/IP implementation in the MD-DOS/IP package. The analysis shows that the TCP flow control mechanism has a severely negative impact on the performance. The TCP data copy and checksum are the major overheads of TCP segment processing. Finally, the bottleneck of data communication using TCP/IP is identified based on queueing theory and empirical measurements. / Master of Science

Mitchell [1,2] describes end-to-end performance for a LAN-based computer system as the total system throughput and delay for a single-thread transaction. This model is used for a variety of applications. The single-thread transaction might, for example, be a remote database update or a real-time control activity. To model end-to-end performance, one must include the host computers, the network interface units (NIUs), the host-NIU links, and the NIU-NIU links. Based on Jackson's Theorem, total delay for single-thread transaction traversing a computer network can be approximated by the sum of delays in the host computers, the network interface units, the host-NIU links, and the NIU-NIU links. The host computer performance model can be refined by applying execution path analysis. Execution path analysis examines the structure of each software routine to be executed and provides an expression of time delay as a function of probabilities associated with conditional branches and a function of data input size. Spreadsheet models provide quick and convenient solutions for purposes of performing computer system tuning and capacity planning as demonstrated by Thomas [10]. This thesis paper extends the typical modeling approach by providing more detailed analysis of host computer delay, more specifically, the execution path analysis. In addition, spreadsheet models are implemented to demonstrate the execution path analysis and to provide comparisons with previously implemented models. / Master of Science

This research investigates the implementation and performance of packet video transfer over local area networks. A network architecture is defined for packet video such that most of the processing is performed by the higher layers of the Open Systems Interconnection (OSI) reference model, while the lower layers provide real-time services. Implementation methods are discussed for coding schemes, including data compression, the network interface unit, and the underlying local area network (LAN), Ethernet or the Fiber Distributed Data Interface (FDDI). Performance evaluation is presented using simulation results and analyses for different video sources, implementation models, and LAN s. The simulation experiments are performed for systems where video images are retrieved from databases at one or more servers and delivered over the local area network. / Master of Science

Parallelism can be applied to local area networks to achieve higher data rates using existing hardware technologies. Parallelism can be employed at the different layers of the Open Systems Interconnection (OS1) reference model. This research proposes and analyzes a technique that permits the use of different degrees of parallelism at different protocol layers. A new protocol layer, called the access layer is defined. The protocol and functionality for this layer are defined. The definitions make provision for incorporating an error correction coding procedure known as cross channel coding. A software simulator was built for the proposed parallel network. The simulator has a detailed model of the access layer and was used to verify the functionality defined for the access layer and to estimate the performance of the parallel network. The simulation results indicate that although the access layer processes data in serial, it is not a bottleneck in the parallel system. Other insights obtained from the experiments are also presented. / Master of Science