1,936 research outputs found

    Explicit congestion control algorithms for available bit rate services in asynchronous transfer mode networks

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    Congestion control of available bit rate (ABR) services in asynchronous transfer mode (ATM) networks has been the recent focus of the ATM Forum. The focus of this dissertation is to study the impact of queueing disciplines on ABR service congestion control, and to develop an explicit rate control algorithm. Two queueing disciplines, namely, First-In-First-Out (FIFO) and per-VC (virtual connection) queueing, are examined. Performance in terms of fairness, throughput, cell loss rate, buffer size and network utilization are benchmarked via extensive simulations. Implementation complexity analysis and trade-offs associated with each queueing implementation are addressed. Contrary to the common belief, our investigation demonstrates that per-VC queueing, which is costlier and more complex, does not necessarily provide any significant improvement over simple FIFO queueing. A new ATM switch algorithm is proposed to complement the ABR congestion control standard. The algorithm is designed to work with the rate-based congestion control framework recently recommended by the ATM Forum for ABR services. The algorithm\u27s primary merits are fast convergence, high throughput, high link utilization, and small buffer requirements. Mathematical analysis is done to show that the algorithm converges to the max-min fair allocation rates in finite time, and the convergence time is proportional to the distinct number of fair allocations and the round-trip delays in the network. At the steady state, the algorithm operates without causing any oscillations in rates. The algorithm does not require any parameter tuning, and proves to be very robust in a large ATM network. The impact of ATM switching and ATM layer congestion control on the performance of TCP/IP traffic is studied and the results are presented. The study shows that ATM layer congestion control improves the performance of TCP/IP traffic over ATM, and implementing the proposed switch algorithm drastically reduces the required switch buffer requirements. In order to validate claims, many benchmark ATM networks are simulated, and the performance of the switch is evaluated in terms of fairness, link utilization, response time, and buffer size requirements. In terms of performance and complexity, the algorithm proposed here offers many advantages over other proposed algorithms in the literature

    TCP/IP traffic over ATM network with ABR flow and congestion control

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    Most traffics over the existing ATM network are generated by applications running over TCP/IP protocol stack. In the near future, the success of ATM technology will depend largely on how well it supports the huge legacy of existing TCP/IP applications. In this thesis, we study and compare the performance of TCP/IP traffic running on different rate based ABR flow control algorithms such as EFCI, ERICA and FMMRA by extensive simulations. Infinite source-end traffic behavior is chosen to represent, FTP application running on TCP/IP. Background VBR traffic with different ON-OFF frequency is introduced to produce transient network states as well as congestion. The simulations produce many insights on issues such as: ABR queue length in congested ATM switch, source-end ACR (Allowed Cell Rate), link utilization at congestion point, efficient end to end TCP throughput, the TCP congestion control window size, and the TCP round trip time. Based on the simulation results, zero cell loss switch buffer requirement of the three algorithms are compared, and the fairness of ABR bandwidth allocation among TCP connections are analyzed. The interaction between the TCP layer and the ATM layer flow and congestion control mechanism is analyzed. Our simulation results show that in order to get a good TCP throughput and affordable switch buffer requirement, some kind of switch queue length monitoring and control mechanism is necessary in the ABR. congestion algorithm

    Message-Bundle Converting in Intenet Protocol Multicast-Based High Level Architecture Exercises

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    The Department of Defense is pushing for more wide-spread and realistic interactive training simulations which increases the demand on network capacity and resources. While network bandwidth is a measurable resource, packet bandwidth, or the number of packets-per-second (Pk/s) a host can handle, is a shifting commodity. This research analyzes host performance characteristics under varying data loads. The hosts include SGI single and multi-processor systems and Intel Pentium platforms using both Windows 95 and Linux Operating Systems. The networking media covers Ethernet, ATM and FDDI. For the ATM network, both AAL5 and IP over ATM were analyzed. With the data from this research, a system is proposed and developed that takes individual messages and bundles them into multi-message packets. This bundling process overcomes the 5,000 Pk/s limitation, reduces the CPU network handling time and introduces a flow-control mechanism at the local network level. While the idea of bundling messages to increase CPU efficiency is not new, there are no current methods of bundling within the new High Level Architecture (HLA). This proposed process is a novel approach to introduce flow control, priority message handling and increase address space while utilizing bundled data delivery. For traditional network delivery, typical CPU usage from network data varies as a function of traffic load, ranging from 5% at 500 messages-per-second to over 80% at 4,000 messages-per-second. The new bundling process requires 10% at 500 messages-per-second but only increases to 13% at 4,000 messages-per-second

    Center for Aeronautics and Space Information Sciences

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    This report summarizes the research done during 1991/92 under the Center for Aeronautics and Space Information Science (CASIS) program. The topics covered are computer architecture, networking, and neural nets

    Performance study of voice over frame relay : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Information Engineering, Massey University, Albany, New Zealand

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    Frame Relay (FR) represents an important paradigm shift in modern telecommunication. This technology is beginning to evolve from data only application to broad spectrum of multimedia users and potential to provide end users with cost effective transport of voice traffic for intra office communication. In this project the recent development in voice communication over Frame relay is investigated. Simulations were carried out using OPNET, a powerful simulation software. Following the simulation model, a practical design of the LAN-to-LAN connectivity experiment was also done in the Net Lab. From the results of the simulation, Performance measures such as delay, jitter, and throughput are reported. It is evident from the results that real-time voice or video across a frame relay network can provide acceptable performance
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