TCP-Friendly Congestion Control over Wireless Networks (original) (raw)
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International Journal of Communications, Network and System Sciences, 2015
This paper presents a sender side only TCP mechanism to prevent compromise for bandwidth utilization in IEEE 802.11 wireless networks. In absence of mechanism for accurate and immediate loss discrimination, the TCP sender unnecessarily reduces its Loss Window in response to the packet losses due to transmission errors. At the same time, frequent transmission losses and associated link retransmissions cause inaccuracy for available bandwidth estimate. The proposal, Adaptive TCP tackles the above issues using two refinements. First, sender estimates the degree of congestion by exploiting the statistics for estimated Round Trip Time (RTT). With this, it prevents unnecessary shrinkage of Loss Window and bandwidth estimate. Second, by concluding the uninterrupted evolution of its sending rate in recent past, the Adaptive TCP advances bandwidth estimate under favorable network conditions. This in turn, facilitates for quick growth in TCP's sending rate after loss recovery and consequently alleviates bandwidth utilization. The authors implement the algorithm on top of TCP NewReno, evaluate and compare its performance with the wireless TCP variants deployed in current Internet. Through intensive simulations it is demonstrated that the Adaptive TCP outperforms other well-established TCP variants, and yields more than 100% of the throughput performance and more than 60% of improvement for bandwidth utilization, compared to TCP NewReno. The simulation results also demonstrated compatibility of Adaptive TCP in a shared wireless environment.
An Efficient Congestion Control Protocol for Wired/Wireless Networks
Recently, wide spectrum of heterogeneous wireless access networks integrate with high speed wired networks to deliver Internet services. End-to-end service delivery with satisfactory quality is challenging issue in such network architectures. Although the Internet transport control protocol (TCP) addresses such challenge, it has poor performance with high speed wired networks (i.e. high bandwidth-delay product). Moreover, it behaves badly with wireless access networks (i.e. misinterpretation of packet loss occurrence that could be interpreted in wrong way as network congestion). Thus, adapting TCP in terns of accurate interpretation of network status has drawn a significant attention. This paper addresses the problem of adapting congestion window size as an interpretation of frequent fluctuations of network load. The work in this paper proposes congestion window size (cwnd) adjustment in terms of instantaneous network load (i.e. bandwidth estimation). The aims are to improve End-to-End TCP throughput as well as maximum resource utilization. With different scenarios, NS-2 simulator has been adopted to evaluate proposed TCP protocol. Notable improvement has been demonstrated by comparing proposed protocol to TCP NewReno benchmark and TCP Vegas.
TCP Performance Dynamics and Link-Layer Adaptation Based Optimization Methods for Wireless Networks
IEEE Transactions on Wireless Communications, 2000
Almost a decade long research on the performance of TCP in wireless networks has resulted in many proposals and solutions [1]-[9] to the problem of TCP throughput degradation. Several of these measures, however, have their share of drawbacks. With the continuing emergence of wireless technologies ever since the work on TCP performance over wireless began, smart link-layer mechanisms like adaptive modulation and coding, power control, and incremental redundancy have been designed and deployed. In this work, we outline a cross-layer optimization framework based on the congestion control dynamics of a bulk-transfer TCP flow and demonstrate its application to networks which offer link-layer adaptive measures. We begin by observing that the TCP's congestion window dynamics are comprised of certain recurring patterns which we term as cycles. We then overlay a TCP throughput optimization methodology that selects link-layer transmission modes (e.g. modulation scheme, coding rate, transmission power, or a combination thereof) in accordance with TCP dynamics and wireless channel conditions. We provide insights into the working of the optimization procedure which protects TCP segments against losses on the wireless channel when the TCP congestion window size (in bytes) is below the bandwidth-delay product of the network. The protection against wireless channel losses is rendered by the link-layer by employing robust modulation and coding schemes, high transmission power, etc. We show that TCP dynamics aware link adaptation measures lead to substantial enhancement of TCP throughput in EGPRS and IEEE 802.11a networks.
On the Performance of Congestion Control Protocols in Lossy Wireless Networks ( Invited Paper )
2007
To cope with link errors in wireless networks, endto-end solutions (e.g., TCP Westwood and TCP Veno) as well as router feedback-based solutions have been proposed. In this paper, we focus on the merits behind the use of router feedbackbased approaches to tackle congestion and link errors in wireless environments. Firstly, some of the end-to-end improvements to TCP are presented and their strengths and drawbacks are discussed. Secondly, router feedback-based methods are introduced. It is shown that proactive window adjustment methods based on the fed back information are able to achieve high throughput even in high link error environments. Finally, we discuss the importance of router feedback-based mechanisms and discuss the required features for a scalable and feasible feedback mechanism.
TCP’s dynamic adjustment of transmission rate to packet losses in wireless networks
EURASIP Journal on Wireless Communications and Networking
Based on the assumption of transmission control protocol (TCP) that packets are lost due to congestion, TCP’s congestion control algorithms such as fast retransmit/recovery (FRR) and retransmission timeouts (RTO) unconditionally reduce the transmission rate for every packet loss. When TCP operates in wireless networks, however, FRRs/RTOs are often triggered regardless of congestion due to sudden delay and wireless transmission errors. The congestion irrelative FRRs/RTOs incur TCP’s misbehavior such as blindly halving the transmission rate, unnecessarily retransmitting the outstanding packets which may be in the bottleneck queue. Although many previous studies have been proposed to detect the congestion irrelative FRRs/RTOs, they paid little attention on effectively adjusting the transmission rate for the detected congestion irrelative FRRs/RTOs. In this article, we propose an enhanced TCP to dynamically adjust its transmission rate according to network conditions. Our scheme adjusts...
TCP cross layer adaptive policy: Throughput optimization over wireless links
2010 National Conference On Communications (NCC), 2010
TCP is the most common transport layer protocol used in Internet. It was designed primarily for wired networks, assuming reliability at lower layers and packet losses are considered as an indication of congestion. The characteristic of wireless links is very different from wired links, particularly in terms of loss behavior. In wireless networks, most packet losses are due to poor link quality and intermittent connectivity, which TCP may falsely assume as congestion. These wrongly trigger the congestion control mechanism of TCP, resulting into end-to-end throughput degradation. The problem is further compounded by the large propagation delay common in such environments. TCP-ACC proposed earlier attempts to combat this problem by adopting a dynamic value of congestion window for the slow start. In this paper, we extend TCP-ACC with the help of a cross layer solution to differentiate between a loss due to congestion and a loss due to noise in the wireless link based on the number of attempts of MAC layer retransmissions.
Wireless Networks, 2010
Link Adaptation is a radio resource management technique that assesses the channel conditions and selects a transport mode, from a set of possible options, which is optimised for these conditions according to a predefined criterion. The optimum transport mode is commonly determined so as to maximise the throughput. Although this approach may be appropriate for best-effort services, its suitability for multimedia services, usually characterised by tight delay and error performance constraints, has been questioned. As a result, a number of alternative algorithms have been proposed in the literature. In this context, this paper presents and evaluates in a dynamic radio environment several Link Adaptation algorithms designed to enhance the provision of delay-and error-sensitive multimedia packet-data services over wireless systems. The obtained results demonstrate that significant improvements in terms of throughput, transmission delay, error performance and operation of Link Adaptation itself can be obtained with the proposed schemes.
TCP CERL: congestion control enhancement over wireless networks
Wireless Networks, 2010
In this paper, we propose and verify a modified version of TCP Reno that we call TCP Congestion Control Enhancement for Random Loss (CERL). We compare the performance of TCP CERL, using simulations conducted in ns-2, to the following other TCP variants: TCP Reno, TCP NewReno, TCP Vegas, TCP WestwoodNR and TCP Veno. TCP CERL is a sender-side modification of TCP Reno. It improves the performance of TCP in wireless networks subject to random losses. It utilizes the RTT measurements made throughout the duration of the connection to estimate the queue length of the link, and then estimates the congestion status. By distinguishing random losses from congestion losses based on a dynamically set threshold value, TCP CERL successfully attacks the well-known performance degradation issue of TCP over channels subject to random losses. Unlike other TCP variants, TCP CERL doesn't reduce the congestion window and slow start threshold when random loss is detected. It is very simple to implement, yet provides a significant throughput gain over the other TCP variants mentioned above. In single connection tests,
Cross-Layer Design to Improve Wireless TCP Performance with Link-Layer Adaptation
2007 IEEE 66th Vehicular Technology Conference, 2007
Transmission Control Protocol (TCP), the almost universally used reliable transport protocol in the Internet, has been engineered to perform well in wired networks where packet loss is mainly due to congestion. TCP throughput, however, degrades over wireless links, which are characterized by a high and greatly varying bit error rate and by intermittent connectivity. Over such wireless links, the performance achieved by TCP can be improved through the use of cross-layer algorithms at the link-level, which interact with the TCP state machine. In this paper, a TCP-aware dynamic ARQ algorithm is therefore proposed, which utilizes TCP timing information to prioritize ARQ packet retransmissions. Numerical investigation of the proposed algorithm demonstrates the performance improvements that can be attained through this approach, in comparison with TCP-agnostic link-layer approaches.
Performance Analysis and Optimization of TCP over Adaptive Wireless Links
2006
This paper proposes an analytical framework for performance evaluation of TCP (Transport Control Protocol) over adaptive wireless links. Specifically, we include adaptation of power, modulation format and error recovery strategy, and incorporate some features of wireless fading channels. This framework is then used to pursue joint optimization through maximization of an objective functional, that expresses a trade-off between achievable throughput and energy costs. A set of numerical results is reported, and it is seen that Hybrid ARQ schemes may provide significant benefits in the optimization framework.