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OPNET Technologies © 2008 OPNET Technologies, Inc. |
Title: A Resilient Transport Control Scheme for Metro Ethernet Services This paper aims to enhance the transport services of Ethernet MANs by utilizing SLA information to control traffic more intelligently, to detect congestion more accurately, and to handle packet losses more adaptively. Ethernet services convert Ethernet from a best effort technology to a service level agreement (SLA) driven carrier-grade technology, extending the simplicity and flexibility of Ethernet beyond the LAN to the MAN/WAN. Although current bandwidth allocation schemes are able to reassign idle capacity and provide QoS at link layer, the end-to-end throughput in the application layer is not optimized. The performance of TCP over SLA driven Ethernet services is not adequate, because the mechanisms of TCP are designed for best effort networks. Because of the stochastic nature of Ethernet networks, a small but non-zero random loss rate is inevitable, which can be tolerated by Ethernet services, but not by TCP. In this paper, a novel SLA-aware transport control scheme is proposed to utilize reserved bandwidth more efficiently using a shifted additive increase multiplicative decrease (AIMD) algorithm, and to detect congestion more accurately using a new decision rule based on hypothesis test. The new congestion control method can keep false-alarm probability under control and therefore it increases throughput significantly. The performance of the proposed scheme is compared with traditional TCP through theoretical analyses and simulations.
Title: Simulation Study of TCP Acceleration Mechanisms for Broadband Access Networks TCP acceleration is an approach to increase TCP throughput through network processing. A TCP proxy located in a network node (such as DSLAM) intercepts and relays TCP connections between the client and the server. Because the proxy acknowledges and retransmits segments faster, TCP acceleration increases throughput and reduces congestion. Moreover, the network characteristics of the access networks and the core networks are quite different. Using two different TCP flavors could optimize the end-to-end performance. In this work, we implement a TCP accelerator node module, and present a deep investigation on how the TCP acceleration improves TCP performance in broadband access. Other Simulations: Title: Ant Routing Algorithm Simulation using OPNET Several routing protocols exist for large networks, Open Shortest Path First (OSPF) has been one of the most commonly used. Another technique that could serve a similar purpose is the new Ant Routing Algorithm. This is an adaptive routing technique based on the way ants forage. One of the most distinguished characteristics of this algorithm is that it stores a pheromone variable in each switching node and increments this variable depending on the amount of traffic that flows through the node. After a finite period of time the system will reach a steady-state in which the shortest path has the highest amount of traffic flow. This project presents some simulations results based on the combination of ideas that the authors of this paper gathered into one algorithm. A brief description of OPNET is also provided to the reader. From the results we discuss some of the pros and cons of implementing this routing protocol into an existing network.
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