Network flow control is formulated as a global optimization problem of user profit. A general global optimization flow control model is established. This model combined with the stochastic model of TCP is used to stud...Network flow control is formulated as a global optimization problem of user profit. A general global optimization flow control model is established. This model combined with the stochastic model of TCP is used to study the global rate allocation characteristic of TCP. Analysis shows when active queue management is used in network TCP rates tend to be allocated to maximize the aggregate of a user utility functionU s (called,U s fairness). The TCP throughput formula is derived An improved TCP congestion control mechanism is proposed. Simulations show its throughput is TCP friendly when competing with existing TCP and its rate change is smoother. Therefore, it is suitable to carry multimedia applications.展开更多
Transmission Control Protocol (TCP) performance over MANET is an area of extensive research. Congestion control mechanisms are major components of TCP which affect its performance. The improvement of these mechanisms ...Transmission Control Protocol (TCP) performance over MANET is an area of extensive research. Congestion control mechanisms are major components of TCP which affect its performance. The improvement of these mechanisms represents a big challenge especially over wireless environments. Additive Increase Multiplicative Decrease (AIMD) mechanisms control the amount of increment and decrement of the transmission rate as a response to changes in the level of contention on routers buffer space and links bandwidth. The role of an AIMD mechanism in transmitting the proper amount of data is not easy, especially over MANET. This is because MANET has a very dynamic topology and high bit error rate wireless links that cause packet loss. Such a loss could be misinterpreted as severe congestion by the transmitting TCP node. This leads to unnecessary sharp reduction in the transmission rate which could degrades TCP throughput. This paper introduces a new AIMD algorithm that takes the number of already received duplicated ACK, when a timeout takes place, into account in deciding the amount of multiplicative decrease. Specifically, it decides the point from which Slow-start mechanism should begin its recovery of the congestion window size. The new AIMD algorithm has been developed as a new TCP variant which we call TCP Karak. The aim of TCP Karak is to be more adaptive to mobile wireless networks conditions by being able to distinguish between loss due to severe congestion and that due to link breakages or bit errors. Several simulated experiments have been conducted to evaluate TCP Karak and compare its performance with TCP NewReno. Results have shown that TCP Karak is able to achieve higher throughput and goodput than TCP NewReno under various mobility speeds, traffic loads, and bit error rates.展开更多
A congestion control algorithm is proposed for resilient packet ring (RPR) in this paper. In this algorithm, nonlinear explicit rate feedback control is used to ensure fast convergence and smooth equilibrium behavior....A congestion control algorithm is proposed for resilient packet ring (RPR) in this paper. In this algorithm, nonlinear explicit rate feedback control is used to ensure fast convergence and smooth equilibrium behavior. The algorithm combines explicit rate control with a deficit round robin (DRR) scheduler, which not only ensures fairness, but also avoids the implementation difficulties of explicit rate control algorithms. The algorithm has good features of fairness, fast convergence, smooth equilibrium, low queue depth, and easy implementation. It is insensitive to the loss of congestion control packets and can adapt to a wide range of link rates and network scales. It has solved the unbalanced traffic problem of spatial reuse protocol (SRP). The algorithm can be implemented on the multi-access control layer of RPR nodes to ensure fair and efficient access of the best-effort traffic.展开更多
文摘Network flow control is formulated as a global optimization problem of user profit. A general global optimization flow control model is established. This model combined with the stochastic model of TCP is used to study the global rate allocation characteristic of TCP. Analysis shows when active queue management is used in network TCP rates tend to be allocated to maximize the aggregate of a user utility functionU s (called,U s fairness). The TCP throughput formula is derived An improved TCP congestion control mechanism is proposed. Simulations show its throughput is TCP friendly when competing with existing TCP and its rate change is smoother. Therefore, it is suitable to carry multimedia applications.
文摘Transmission Control Protocol (TCP) performance over MANET is an area of extensive research. Congestion control mechanisms are major components of TCP which affect its performance. The improvement of these mechanisms represents a big challenge especially over wireless environments. Additive Increase Multiplicative Decrease (AIMD) mechanisms control the amount of increment and decrement of the transmission rate as a response to changes in the level of contention on routers buffer space and links bandwidth. The role of an AIMD mechanism in transmitting the proper amount of data is not easy, especially over MANET. This is because MANET has a very dynamic topology and high bit error rate wireless links that cause packet loss. Such a loss could be misinterpreted as severe congestion by the transmitting TCP node. This leads to unnecessary sharp reduction in the transmission rate which could degrades TCP throughput. This paper introduces a new AIMD algorithm that takes the number of already received duplicated ACK, when a timeout takes place, into account in deciding the amount of multiplicative decrease. Specifically, it decides the point from which Slow-start mechanism should begin its recovery of the congestion window size. The new AIMD algorithm has been developed as a new TCP variant which we call TCP Karak. The aim of TCP Karak is to be more adaptive to mobile wireless networks conditions by being able to distinguish between loss due to severe congestion and that due to link breakages or bit errors. Several simulated experiments have been conducted to evaluate TCP Karak and compare its performance with TCP NewReno. Results have shown that TCP Karak is able to achieve higher throughput and goodput than TCP NewReno under various mobility speeds, traffic loads, and bit error rates.
基金Supported by the National Natural Science Foundation of China(No.69896242)
文摘A congestion control algorithm is proposed for resilient packet ring (RPR) in this paper. In this algorithm, nonlinear explicit rate feedback control is used to ensure fast convergence and smooth equilibrium behavior. The algorithm combines explicit rate control with a deficit round robin (DRR) scheduler, which not only ensures fairness, but also avoids the implementation difficulties of explicit rate control algorithms. The algorithm has good features of fairness, fast convergence, smooth equilibrium, low queue depth, and easy implementation. It is insensitive to the loss of congestion control packets and can adapt to a wide range of link rates and network scales. It has solved the unbalanced traffic problem of spatial reuse protocol (SRP). The algorithm can be implemented on the multi-access control layer of RPR nodes to ensure fair and efficient access of the best-effort traffic.
