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TCP Vegas exhibits unfair congestion avoidance mechanism, which aggravates when there are insufficient network resources to accommodate buffer space of a pipe (bandwidth delay product). To remedy this shortcoming, we propose an Enhanced VegAs (EVA) that employs three auxiliary mechanisms: Δ revision, congestion detection and congestion tendency detection. A 2k factorial design with replications is used to study the effect of the three mechanisms. Our results show that TCP EVA achieves better performance than Vegas under various network conditions. Furthermore, congestion avoidance schemes, such as TCP EVA, perform much better than congestion control schemes, such as TCP Reno, in resource‐insufficient networks. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Wireless packet ad hoc networks are characterized by multi‐hop wireless connectivity and limited bandwidth competed among neighboring nodes. In this paper, we investigate and evaluate the performance of several prevalent TCP algorithms in this kind of network over the wireless LAN standard IEEE 802.11 MAC layer. After extensively comparing the existing TCP versions (including Tahoe, Reno, New Reno, Sack and Vegas) in simulations, we show that, in most cases, the Vegas version works best. We reveal the reason why other TCP versions perform worse than Vegas and show a method to avoid this by tuning a TCP parameter— maximum window size. Furthermore, we investigate the performance of these TCP algorithms when they run with the delayed acknowledgment (DA) option defined in IETF RFC 1122, which allows the TCP receiver to transmit an ACK for every two incoming packets. We show that the TCP connection can gain 15 to 32 per cent good‐put improvement by using the DA option. For all the TCP versions investigated in this work, the simulation results show that with the maximum window size set at approximately 4, TCP connections perform best and then all these TCP variants differ little in performance. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Stylianos Papanastasiou Mohamed Ould‐Khaoua 《International Journal of Communication Systems》2004,17(2):163-177
Recent research efforts in mobile ad hoc networks have concentrated on examining the behaviour of TCP Reno over various ad hoc routing protocols and have suggested a number of extensions to improve its performance. TCP Vegas, which takes a proactive approach to congestion avoidance, has not so far been examined as a viable alternative to TCP Reno in wireless environments and no effort has been made to analyse its performance over routing protocols for MANETs. This paper evaluates using extensive simulation experiments the performance behaviour of TCP Vegas over a proactive (destination sequenced distance vector) and two reactive (dynamic source routing and ad hoc on demand distance vector) routing protocols and compares it against that of TCP Reno. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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This paper considers the interaction of HTTP with several transport protocols, including TCP, Transaction TCP, a UDP-based request-response protocol, and HTTP with persistent TCP connections. We present an analytic model for each of these protocols and use that model to evaluate network overhead carrying HTTP traffic across a variety of network characteristics. This model includes an analysis of the transient effects of TCP slow-start. We validate this model by comparing it to network packet traces measured with two protocols (HTTP and persistent HTTP) over local and wide-area networks. We show that the model is accurate within 5% of measured performance for wide-area networks, but can underestimate latency when the bandwidth is high and delay is low. We use the model to compare the connection-setup costs of these protocols, bounding the possible performance improvement. We evaluate these costs for a range of network characteristics, finding that setup optimizations are relatively unimportant for current modem, ISDN, and LAN users but can provide moderate to substantial performance improvement over high-speed WANs. We also use the model to predict performance over future network characteristics 相似文献
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Sivakumar Bakthavachalu Miguel A. Labrador 《International Journal of Communication Systems》2004,17(8):763-778
The TFRC protocol has been proposed as a TCP‐friendly protocol to transport streaming media over the Internet. However, its deployment is still questionable because it has not been compared to other important protocols, analysed in the presence of important mechanisms, such as the explicit congestion notification (ECN), and studied under more realistic network conditions. In this paper, we address these three aspects, including other congestion control protocols not considered before in the same investigation, such as TCP Tahoe, Reno, Newreno, Vegas, Sack, GAIMD, and the Binomial algorithms, the effect of using ECN in the friendliness of the protocols, and the fairness of the protocols under static and dynamic network conditions. We found that TFRC can be safely deployed in the Internet if competing with TCP Tahoe, New Reno and SACK since fairness is achieved under all scenarios considered. We also found that ECN actually helps in achieving better fairness. However, fairness problems arise when TFRC competes with TCP Reno, GAIMD, SQRT or IIAD in static or dynamic conditions, or both. We used normalized throughput, fairness index, and convergence time as the main performance metrics for comparison. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Quick User Datagram Protocol (UDP) Internet Connections (QUIC) is an experimental and low‐latency transport protocol proposed by Google, which is still being improved and specified in the Internet Engineering Task Force (IETF). The viewer's quality of experience (QoE) in HTTP adaptive streaming (HAS) applications may be improved with the help of QUIC's low‐latency, improved congestion control, and multiplexing features. We measured the streaming performance of QUIC on wireless and cellular networks in order to understand whether the problems that occur when running HTTP over TCP can be reduced by using HTTP over QUIC. The performance of QUIC was tested in the presence of network interface changes caused by the mobility of the viewer. We observed that QUIC resulted in quicker start of media streams, better streaming, and seeking experience, especially during the higher levels of congestion in the network and had a better performance than TCP when the viewer was mobile and switched between the wireless networks. Furthermore, we measured QUIC's performance in an emulated network that had a various amount of losses and delays to evaluate how QUIC's multiplexing feature would be beneficial for HAS applications. We compared the performance of HAS applications using multiplexing video streams with HTTP/1.1 over multiple TCP connections to HTTP/2 over one TCP connection and to QUIC over one UDP connection. To that effect, we observed that QUIC provided better performance than TCP on a network that had large delays. However, QUIC did not provide a significant improvement when the loss rate was large. Finally, we analyzed the performance of the congestion control mechanisms implemented by QUIC and TCP, and tested their ability to provide fairness among streaming clients. We found that QUIC always provided fairness among QUIC flows, but was not always fair to TCP. 相似文献
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The transmission control protocol (TCP) is one of the most important Internet protocols. It provides reliable transport services between two end‐hosts. Since TCP performance affects overall network performance, many studies have been done to model TCP performance in the steady state. However, recent researches have shown that most TCP flows are short‐lived. Therefore, it is more meaningful to model TCP performance in relation to the initial stage of short‐lived flows. In addition, the next‐generation Internet will be an unified all‐IP network that includes both wireless and wired networks integrated together. In short, modelling short‐lived TCP flows in wireless networks constitutes an important axis of research. In this paper, we propose simple wireless TCP models for short‐lived flows that extend the existing analytical model proposed in [IEEE Commun. Lett. 2002; 6 (2):85–88]. In terms of wireless TCP, we categorized wireless TCP schemes into three types: end‐to‐end scheme, split connection scheme, and local retransmission scheme, which is similar to the classification proposed in [IEEE/ACM Trans. Networking 1997; 756–769]. To validate the proposed models, we performed ns‐2 simulations. The average differences between the session completion time calculated using the proposed model and the simulation result for three schemes are less than 9, 16, and 7 ms, respectively. Consequently, the proposed model provides a satisfactory means of modelling the TCP performance of short‐lived wireless TCP flows. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Congestion control with dynamic threshold adaptation and cross‐layer response for TCP Vegas over IEEE 802.11 wireless networks
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Rung‐Shiang Cheng Der‐Jiunn Deng 《International Journal of Communication Systems》2014,27(11):2918-2930
Wireless technologies provide mobile access and enable rapid andcost‐effective network deployment. But a wireless link is generally accompanied by high interference, transmission errors and a varying latency. The erratic packet losses usually lead to a curbing of the flow of segments on the TCP connection, and thus limit TCP performance. This paper presents a threshold control mechanism with cross‐layer response approach for improving TCP Vegas performance in IEEE 802.11 wireless networks. By making slight modifications to the legacy IEEE 802.11 MAC and TCP, the numerical results reveal that the proposed scheme provides a significant improvement in TCP performance under IEEE 802.11 wireless environments. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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R. Secchi A. C. Mohideen G. Fairhurst 《International Journal of Satellite Communications and Networking》2018,36(1):29-43
Responsiveness is a critical metric for web performance. Recent work in the Internet Engineering Task Force (IETF) and World Wide Web Consortium (W3C) has resulted in a new set of web protocols, including definition of the hypertext transfer protocol version 2 (HTTP/2) and a corresponding set of TCP updates. Together, these have been designed to reduce the web page download latency compared with HTTP/1.1. This paper describes the main features of the new protocols and discusses the impact of path delay on their expected performance. It then presents a set of tests to evaluate whether current implementations of the new protocols can offer benefit with an operational satellite access network and suggests how the specifications can evolve and be tuned to further enhance performance for long network paths. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Analysis of TCP Performance over Mobile Ad Hoc Networks 总被引:27,自引:0,他引:27
Mobile ad hoc networks have attracted attention lately as a means of providing continuous network connectivity to mobile computing devices regardless of physical location. Recent research has focused primarily on the routing protocols needed in such an environment. In this paper, we investigate the effects that link breakage due to mobility has on TCP performance. Through simulation, we show that TCP throughput drops significantly when nodes move, due to TCP's inability to recognize the difference between link failure and congestion. We also analyze specific examples, such as a situation where throughput is zero for a particular connection. We introduce a new metric, expected throughput, for the comparison of throughput in multi-hop networks, and then use this metric to show how the use of explicit link failure notification (ELFN) techniques can significantly improve TCP performance. 相似文献
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移动自组网是由无线移动主机组成的没有基础设施或集中管理中心的临时性网络。在其组建应用过程中,路由协议起着重要的作用。文中基于仿真软件NS2对移动自组网三种典型路由协议DSDV、DSR、TORA在TCP与CBR业务下的性能进行了比较分析。仿真结果表明,在发送速率144kb/s时,DSR与DSDV性能优于TORA,且TCP业务性能优于CBR业务。 相似文献
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Many previous studies have indicated that TCP Vegas outperforms TCP Reno. This letter shows that in asymmetric networks in which the bottleneck is on the reverse path rather than on the forward path, Vegas underutilizes the available bandwidth on the forward path by a large margin. A solution that makes use of the TCP timestamp option can effectively restore the throughput on the forward path. 相似文献
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This works aims at evaluating achievable performance for TCP/IP data transfer over DECT radio interface, by verifying the ability of DECT lower layers protocols, namely DLC and MAC, to mask the radio interface unreliability and to provide flexible transfer means for TCP data. Major points are: (i) the interplay of error recovery mechanisms at the various layers; (ii) the effectiveness of providing multibearer capabilities (i.e. allowing slot bundling in the radio access); (iii) the possible gains brought about by MAC asymmetric connections in view of essentially asymmetric TCP data flows.Obtained results indicate that satisfactory performance can be obtained, since the lower layers recovery functions are able to mask even a rather pessimistic radio channel behavior as here assumed. This comes at the price of about half of the gross available capacity, because of static overhead and radio channel impairments, which is anyway in the order of (often less than) typical overhead due to radiocommunication protecting codes, e.g., as defined in GSM, UMTS, CDPD. 相似文献
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为了深入理解编码TCP的原理,在讨论TCP Vegas协议和网络编码的基本形式的基础上,分别从无线网络发送端和接收端的角度深入论述了其与网络编码的融合方法以及网络编码层的结构和控制机理,在最后提出了NS2模拟软件底层代码的修改思路来实现检测网络编码TCP性能的目的。 相似文献