Local area networks (Computer networks)

The statistics of random sum is studied and used to evaluate performance metrics
in wireless networks. Pertinent wireless network performance measures such as call
completion/dropping probabilities and the average number of handovers usually require
the probability distributions of the cell dwell time and call holding time; and are therefore
not easy to evaluate. The proposed performance evaluation technique requires the
moments of the cell dwell time and is given in terms of the Laplace transform function of
the call holding time. Multimedia services that have Weibull and generalized gamma
distributed call holding times are investigated. The proposed approximation method uses
the compound geometric random sum distribution and requires that the geometric
parameter be very small. For applications in which this parameter is not sufficiently
small, a result is derived that improves the accuracy (to order of the geometric parameter)
of the performance measures evaluated.

Designing a dependable network for a highly sustainable system gives a challenging network design problem. The network must be highly adaptive to the changes in the network environment. It should also sustain any damages occurring in the network and recover itself quickly and efficiently. This thesis ultimately maps a real network to simulated network by developing a concept of generic nodes and experimentally investigates different parameters that affects the reliability of the system. The work includes designing a simulation for generation of network traffic in a simulated network and studying the behavior of the network with different parameters. The experiment helped us in determining the optimum values of these parameters. For the selected set of experiments and further implies that simulation can determine the nodes different parameter in a control network and will result in a Dependable system.

Over the past ten years, Client/Server computing has had a powerful impact on the way businesses deal with information technology. Client/Server computing has enhanced user's productivity, revolutionized computer networking, and restructured the computer industry. Today, another new technology is poised to impact business computing in an equally dramatic way. Networked Multimedia computer applications will significantly affect users and network managers and have a tremendous impact on computing and network infrastructures. This thesis explores the areas of high speed networking for multimedia applications. Focusing primarily on the FDDI technology we model a high speed FDDI multimedia LAN model and developed typical multimedia traffic models to aid in case study of the FDDI HSMM-LAN networks. FFOL, the Follow On Standards currently in the ANSI standards committee, discuss Network Architectures that include a gigabit backbone network for FDDI and FDDI II networks, making them an attractive and cost effective option to the customer.

Capture effect has shown considerable improvement on performance of slotted ALOHA systems. Further, improvement is expected by increasing the number of base stations. The performance of such slotted ALOHA systems is analyzed with the aid of Equilibrium point analysis. Packet dropping due to finite number of retransmissions is taken into account. The numerical results indicate that the finite number of retransmission trials mainly contribute to the improvement of the packet dropping probability in the range of light input traffic. The use of multiple base stations improves the overall throughput and the average transmission delay in the range of heavy input traffic.

In this thesis we have proposed and analyzed a new architecture for high speed fiber optic LANs/MANs, called the Dual Bus R-Net. The scheme is based on a slotted unidirectional dual bus structure. It uses a reservation mechanism to generate slotted frames on each bus. Frames consist of a reservation slot and one or many information slots. Stations reserve slots by transmitting reservation requests on the bus carrying information in the opposite direction. The scheme has the advantage of superior channel utilization, bounded delay, fair access to all stations, dynamic bandwidth allocation to network users, and implementation simplicity. Extensive simulations have been carried out to verify the characteristics of the network. Simulation results reinforce the initial claims of the advantages offered by Dual Bus R-Net. Performance analysis is presented in terms of network delay and channel utilization. Simulation results are compared with similar results of X-Net, R-Net, DQDB, and Expressnet.

The primary emphasis of this thesis is to study the behavioral characteristics of Fiber Distributed Data Interface (FDDI) and Distributed Queue Dual Bus (DQDB) High Speed Local Area Networks (HSLANs). An FDDI architecture with passive interfaces is proposed to provide a reliable and efficient network topology. This network architecture outperforms the existing FDDI architecture with active interfaces in terms of small asynchronous packet delays and high asynchronous packet throughput. The design and implementation issues involved in the design of the hierarchical (multi-level) DQDB and FDDI networks are also presented. The hierarchical network architecture provides modularity and scalability with respect to speed and the number of users. Simulation models are developed for each of these network architectures to study their performance. Simulation results are presented in terms of medium access delay, throughput, and packet delays.

A new topology is proposed that is regular in structure and allows broadband Local Area Networks to be connected together to support a large number of users. The topology is based on connecting local area networks in cube fashion and allows for systematic growth as the need arises. These cubes are attached to each other as building blocks by adding cubes evenly in all three dimensions. In an operational network, irregularities occur due to failures at gateways. An addressing scheme and an automatic routing algorithm are developed that makes it possible to add new users without affecting the addresses of existing nodes. The capacity of the proposed networking architecture is determined and compares favorably to that of hypercube interconnected LANs when the number of rings in the network is small.

A unified performance analysis of token-passing local area networks is reported in this thesis. The primary performance criterion is the mean transfer delay of a message, which is defined as the time from the instant a message becomes available for transmission at a station until the end of its successful reception at the destination. Other performance criteria are power and effective transmission ratio. Analytical expressions for the criteria are derived for exhaustive, gated, and limited service disciplines. Simulation models are also used to support the investigations. The effects of service time distribution (constant, exponential, and hyperexponential) are examined. It is found that under any traffic intensity, service discipline or packet length distribution, token bus gives higher delay and has lower power and lower effective transmission ratio than token ring. Also, the token bus is found to be less sensitive to message length distribution, performing about the same for constant, exponential, and hyperexponential distribution.

The primary emphasis of this thesis is to evaluate in comparative terms the performance of three types of service disciplines in a Token Ring Local Area Network. The service disciplines studied are exhaustive, gated and limited service. These service disciplines play an important role in the network performance, especially when some users are relatively less active than others in contributing traffic load to the network. Network performance for these service disciplines are compared to determine which one of them gives better performance. Simulation is used for this study and results are presented in terms of average delay, queue lengths and delay histograms versus traffic intensity.