Browsing by Author "Ho, CY"

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A TCP-friendly stateless AQM scheme for fair bandwidth allocation
(2005)
Ho, CY
;
Chan, YC
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
Queue management, bandwidth share, and congestion control are very important to both robustness and fairness of the Internet. In this article, we investigate the problem of providing a fair bandwidth allocation to those flows that share congested link in a router A new TCP-friendly router-based AQM (active queue management) scheme, termed WARD, is proposed to approximate the fair queueing policy. WARD is a simple packet dropping algorithm with a random mechanism, and discriminates against the flows which transmit more packets than allowed. By doing this, it not only protects TCP connections from UDP flows, but also solves the problem of competing bandwidth among different TCP versions such as TCP Vegas and Reno. In addition, WARD works quite well for TCP flow isolation even with different round trip times. In other words, WARD improves the unfair bandwidth allocation properties. Furthermore, it is stateless and easy to implement, so WARD controls unresponsive or misbehaving flows with a minimum overhead.
An aided congestion avoidance mechanism for TCP Vegas
(2005-01-01)
Ho, CY
;
Shih, CH
;
Chen, YC
;
Chan, YC
;
資訊工程學系
TCP Vegas detects network congestion in the early stage and successfully prevents periodic packet loss that usually occurs in TCP Reno. It has been demonstrated that TCP Vegas achieves much higher performance than TCP Reno in many aspects. However, TCP Vegas cannot prevent unnecessary throughput degradation when congestion occurs in the backward path, it passes through multiple congested links, or it reroutes through a path with longer round-trip time (RTT). In this paper, we propose an aided congestion avoidance mechanism for TCP Vegas, called Aid-Vegas, which uses the relative one-way delay of each packet along the forward path to distinguish whether congestion occurs or not. Through the results of simulation, we demonstrate that Aid-Vegas can solve the problems of rerouting and backward congestion, enhance the fairness among the competitive connections, and improve the throughput when multiple congested links are encountered.
An aided congestion avoidance mechanism for TCP Vegas
(2005-01-01)
Ho, CY
;
Shih, CH
;
Chen, YC
;
Chan, YC
;
交大名義發表
TCP Vegas detects network congestion in the early stage and successfully prevents periodic packet loss that usually occurs in TCP Reno. It has been demonstrated that TCP Vegas achieves much higher performance than TCP Reno in many aspects. However, TCP Vegas cannot prevent unnecessary throughput degradation when congestion occurs in the backward path, it passes through multiple congested links, or it reroutes through a path with longer round-trip time (RTT). In this paper, we propose an aided congestion avoidance mechanism for TCP Vegas, called Aid-Vegas, which uses the relative one-way delay of each packet along the forward path to distinguish whether congestion occurs or not. Through the results of simulation, we demonstrate that Aid-Vegas can solve the problems of rerouting and backward congestion, enhance the fairness among the competitive connections, and improve the throughput when multiple congested links are encountered.
An efficient mechanism of TCP-Vegas on mobile IP networks
(2005)
Ho, CY
;
Chan, YC
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
Mobile IP network provides hosts the connectivity to the Internet while changing locations. However, when using TCP Vegas over a mobile network, it may respond to a handoff by invoking a congestion control algorithm, thereby resulting in performance degradation, because TCP Vegas is sensitive to the change of RTT (Round-Trip Time) and it may recognize the increased RTT as a result of network congestion. Since TCP Vegas could not differentiate whether the increased RTT is due to route change or network congestion. This work investigates how to improve the performance of Vegas after a Mobile IP handoff and proposes a variation of TCP Vegas, so-called Demo-Vegas, which is able to detect the movement of two end-hosts of a connection, and re-measure the BaseRTT (Minimum Round-Trip Time) if necessary. The proposed mechanism maintains end-to-end semantics, and operates under the existing network infrastructure. Demo-Vegas presents a simple modification in the two end sides of a connection and uses one reserved bit in TCP header. Simulation results demonstrate that Demo-Vegas features higher performance than Vegas in Mobile IP networks.
An enhanced slow-start mechanism for TCP Vegas
(2005)
Ho, CY
;
Chan, YC
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
In this article, we present a new slow-start variant, which improves the throughput of TCP Vegas, we call this new mechanism Gallop-Vegas which quickly ramps up to the available bandwidth and reduces the burstiness during the slow-start phase. Since TCP (Transmission Control Protocol) is known to send bursts of packets during its slow-start phase due to the fast increase of window size and the ACK-clock based transmission. This phenomenon causes TCP Vegas to change from slow-start phase to congestion-avoidance phase too early in the large BDP (bandwidth-delay product) links. Therefore, in Gallop-Vegas, we increase the congestion window size with a rate between exponential growth and linear growth during slow-start phase. Our extensive simulation results show that GallopVegas significantly improves the performance during the slow-start phase. Furthermore, it is implementation feasible because only sending part needs to be modified.
Distributed motion control using real-time network communication techniques
(2000)
Lin, SY
;
Ho, CY
;
Tzou, YY
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電控工程研究所
;
Institute of Electrical and Control Engineering
This paper presents a survey of the applications of real-time network control technology to advanced digital motion control system. Applications of PROFIBUS, FIP, CAN bus, Interbus-S, SERCOS, and Ethernet to coordinated motion control have been studied. Realization issues in application of real-time network control for motor drives and coordinated motion control systems are discussed. Future development trend of realtime network for motion control has been forecasted.
Performance improvement of congestion avoidance mechanism for TCP vegas
(2004)
Chan, YC
;
Chan, CT
;
Chen, YC
;
Ho, CY
;
資訊工程學系
In this paper we propose a router-based congestion avoidance mechanism (RoVegas) for TCP Vegas. TCP Vegas detects network congestion in the early stage and successfully prevents periodic packet loss that usually occurs in TCP Reno. It has been demonstrated that TCP Vegas outperforms TCP Reno in many aspects. However TCP Vegas suffers several problems that inhere in its congestion avoidance mechanism, these include issues of rerouting, persistent congestion, fairness, and network asymmetry. By performing the proposed scheme in routers along the round-trip path, RoVegas can solve the problems of rerouting and persistent congestion, enhance the fairness among the competitive connections, and improve the throughput when congestion occurs on the backward path. Through the results of both analysis and simulation, we demonstrate the effectiveness of RoVegas.
Snug-Vegas and Snug-Reno: efficient mechanisms for performance improvement of TCP over heterogeneous networks
(2006-04-01)
Ho, CY
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
Improving the performance of the traditional TCP in wireless IP communications has been an active research area. The significant cause of packet losses in such heterogenous networks is no longer limited to network congestion. The performance degradation of TCP in wireless and wired-wireless hybrid networks is mainly due to its lack of ability to differentiate the packet losses caused by network congestions from the losses caused by wireless link errors. New variants of TCP Vegas and TCP Reno named Snug-Vegas and Snug-Reno, respectively, are proposed. By using random-loss indications marked by base stations, Snug-Vegas and Snug-Reno may detect random packet losses precisely. Through the packet loss differentiation, Snug-Vegas and Snug-Reno react appropriately to the losses, and based on the simulation results, it is seen that the throughput of connection over heterogeneous networks can be significantly improved.