A multilayer IP security protocol for TCP performance enhancement in wireless networks

Transmission control protocol (TCP) performance enhancement proxy (PEP) mechanisms have been proposed, and in some cases widely deployed, to improve TCP performance in all-Internet protocol (IP) wireless networks. However, this technique is conflicted with IP-security (IPsec)-a standard IP security protocol that will make inroad into wireless networks. This paper analyzes the fundamental problem behind this conflict and develops a solution called multilayer IP-security (ML-IPsec). The basic principle is to use a multilayer protection model and a fine grain access control to make IP security protocols compatible with TCP PEP. It allows wireless network operators or service providers to grant base stations or wireless routers limited and controllable access to the TCP headers for performance enhancement purposes. Through careful design, implementation, and evaluation, we show that we can easily add ML-IPsec to existing IPsec software and the overhead is low. We conclude that ML-IPsec can help wireless networks provide both security and performance.     

On TCP performance enhancing proxies in a wireless environment

TCP performance enhancement in wireless access networks is an important ongoing area of research. It is known that the hostile nature of the wireless channel and the mobile nature of wireless users interact adversely with standard TCP congestion control mechanisms [1], causing a drastic reduction in throughput. This article surveys a selection of different approaches to managing TCP performance over wireless links, and presents the results of simulation and field trial results of a novel TCP performance enhancing proxy over diverse cellular radio access technologies based on the GSM, cdma2000, and UMTS standards. The proposed TRL TCP performance enhancing proxy has the advantages of being completely transparent to both TCP endpoints and tunable to different access technologies, and frequently achieves the maximum throughput available from any of the studied radio access technologies.     

无线网络中TCP与Ipsec的兼容性研究

针对有线网络设计的传输控制协议(TCP),在应用到无线环境中时存在许多不兼容问题,必须对TCP进行修改.目前人们提出了几种对TCP协议在无线网络环境下的改进方案,但是这些改进方案同IP安全协议(IPsec)存在一定的中突.文章分析了IPsec与TCP的改进方案之间的冲突问题,给出了4种解决方案:用传输层安全协议/安全套接层协议(TLS/SSL)代替IPsec、扩展封装安全载荷(ESP)协议、对TCP路径分段和修改IPsec的端到端保护模式,并分析了各方案的优缺点.     

Enhancing Fairness and Throughput of TCP in Heterogeneous Wireless Access Networks

Most of the recent research on TCP over heterogeneous wireless networks has concentrated on differentiating between packet drops caused by congestion and link errors, to avoid significant throughput degradations due to the TCP sending window being frequently shut down, in response to packet losses caused not by congestion but by transmission errors over wireless links. However, TCP also exhibits inherent unfairness toward connections with long round-trip times or traversing multiple congested routers. This problem is aggravated by the difference of bit-error rates between wired and wireless links in heterogeneous wireless networks. In this paper, we apply the TCP Bandwidth Allocation (TBA) algorithm, which we have proposed previously, to improve TCP fairness over heterogeneous wireless networks with combined wireless and wireline links. To inform the sender when congestion occurs, we propose to apply Wireless Explicit Congestion Notification (WECN). By controlling the TCP window behavior with TBA and WECN, congestion control and error-loss recovery are effectively separated. Further enhancement is also incorporated to smooth traffic bursts. Simulation results show that not only can the combined TBA and WECN mechanism improve TCP fairness, but it can maintain good throughput performance in the presence of wireless losses as well. A salient feature of TBA is that its main functions are implemented in the access node, thus simplifying the sender-side implementation.     

Internet connection with UMTS

Mobile telecommunication new services are based on data networks specially Internet. These services include http, telnet, ftp, Simple Mail Transfer Protocol, etc. Besides, we recognize a mobile network as a multiuser network. Transmission Control Protocol (TCP)/Internet Protocol which is sensitive to link congestion in wireline data links is also used in wireless networks. In order to improve the system performance, the TCP layer uses flow control and congestion control. Besides, radio link control (RLC) and medium access control sublayers have been introduced to compensate the deficiency of TCP layer in wireless environment. RLC has an important role in quality of service enhancement of the Universal Mobile Telecommunications System (UMTS). In this paper, we review the protocol stack of UMTS Terrestrial Radio Access Network which is based on Third-Generation Partnership Project. Then, we evaluate its layer 2 error control mechanisms and verify TCP over automatic repeat request error control mechanism and finally quality of service improvement results from it in fading channels.     

Optimal design of hybrid FEC/ARQ schemes for TCP over wireless links with Rayleigh fading

In this paper, we investigate interactions between TCP and wireless hybrid FEC/ARQ schemes. The aim is to understand what is the best configuration of the wireless link protocol in order to guarantee TCP performance and channel efficiency. Interactions between TCP and different link layer mechanisms are evaluated by means of an analytic model that reproduces: 1) a Rayleigh fading channel with FEC coding, 2) a generic selective repeat ARQ Protocol, and 3) the TCP behavior in a wired-cum-wireless network scenario. The analytic model is validated-by means of ns-based simulations. The analysis represents a contribution to the optimal design of link layer parameters of wireless networks crossed by TCP/IP traffic. The main findings can be summarized as follows: 1) fully reliable ARQ protocols are the best choice for both TCP performance and wireless link efficiency and 2) optimal values of FEC redundancy degree from the point of view of energy efficiency maximizes TCP performance as well.     

A new ATM adaptation layer for TCP/IP over wireless ATM networks

This paper describes the design and performance of a new ATM adaptation layer protocol (AAL‐T) for improving TCP performance over wireless ATM networks. The wireless links are characterized by higher error rates and burstier error patterns in comparison with the fiber links for which ATM was introduced in the beginning. Since the low performance of TCP over wireless ATM networks is mainly due to the fact that TCP always responds to all packet losses by congestion control, the key idea in the design is to push the error control portion of TCP to the AAL layer so that TCP is only responsible for congestion control. The AAL‐T is based on a novel and reliable ARQ mechanism to support quality‐critical TCP traffic over wireless ATM networks. The proposed AAL protocol has been validated using the OPNET tool with the simulated wireless ATM network. The simulation results show that the AAL‐T provides higher throughput for TCP over wireless ATM networks compared to the existing approach of TCP with AAL 5. This revised version was published online in July 2006 with corrections to the Cover Date.     

An Adaptive Delayed Acknowledgment Strategy to Improve TCP Performance in Multi-hop Wireless Networks

In multi-hop wireless networks, transmission control protocol (TCP) suffers from performance deterioration due to poor wireless channel characteristics. Earlier studies have shown that the small TCP acknowledgments consume as much wireless resources as the long TCP data packets. Moreover, generating an acknowledgment (ACK) for each incoming data packet reduces the performance of TCP. The main factor affecting TCP performance in multi-hop wireless networks is the contention and collision between ACK and data packets that share the same path. Thus, lowering the number of ACKs using the delayed acknowledgment option defined in IETF RFC 1122 will improve TCP performance. However, large cumulative ACKs will induce packet loss due to retransmission time-out at the sender side of TCP. Motivated by this understanding, we propose a new TCP receiver with an adaptive delayed ACK strategy to improve TCP performance in multi-hop wireless networks. Extensive simulations have been done to prove and evaluate our strategy over different topologies. The simulation results demonstrate that our strategy can improve TCP performance significantly.     

Removing redundant TCP functionalities in wired‐cum‐wireless networks with IEEE 802.11e HCCA support

The TCP was originally designed for wired networks, assuming transmission errors were negligible. Actually, any acknowledgment time‐out unconditionally triggers the congestion control mechanism, even in wireless networks in which this assumption is not valid. Consequently, in wireless networks, TCP performance significantly degrades. To avoid this degradation, this paper proposes the so‐called split TCP and UDP. In this approach, the access point splits the TCP connection and uses a customized and lighter transport protocol for the wireless segment. It takes advantage of the IEEE 802.11e Hybrid Coordination Function Controlled Channel Access (HCCA) mechanisms to remove redundant TCP functionalities. Specifically, the HCCA scheduler allows disabling of the congestion control in the wireless link. Similarly, the IEEE 802.11e error control service makes possible to eliminate TCP acknowledgments, therefore reducing the TCP protocol overhead. Finally, the usage of an HCCA scheduler permits providing fairness among the different data flows. The proposed split scheme is evaluated via extensive simulations. Results show that split TCP and User Datagram Protocol outperforms the analyzed TCP flavors—specifically designed for wireless environments—and the split TCP solution, achieving up to 95% of end‐user throughput gain. Furthermore, the proposed solution is TCP friendly because TCP flows are not degraded by the presence of flows by using this approach. Copyright © 2013 John Wiley & Sons, Ltd.     

无线Ad Hoc网中的TCP SACK与TCP Vegas

本文用仿真方法分析了TCP SACK和Vegas在无线ab hoc网络中的性能，提出了一种改进的SACK选项格式（ASACK）和一种称为环回时间通知（RN）的新技术以分别用于提高TCP SACK和TCP Vegas在无线ab hoc网中的性能。为了研究路由稳定性TCP Vegas性能的影响，我们实现了一种基于相关性的选路协议（ABR）。     

Enhancement of TCP over wired/wireless networks with packet loss classifiers inferred by supervised learning

TCP is suboptimal in heterogeneous wired/wireless networks because it reacts in the same way to losses due to congestion and losses due to link errors. In this paper, we propose to improve TCP performance in wired/wireless networks by endowing it with a classifier that can distinguish packet loss causes. In contrast to other proposals we do not change TCP’s congestion control nor TCP’s error recovery. A packet loss whose cause is classified as link error will simply be ignored by TCP’s congestion control and recovered as usual, while a packet loss classified as congestion loss will trigger both mechanisms as usual. To build our classification algorithm, a database of pre-classified losses is gathered by simulating a large set of random network conditions, and classification models are automatically built from this database by using supervised learning methods. Several learning algorithms are compared for this task. Our simulations of different scenarios show that adding such a classifier to TCP can improve the throughput of TCP substantially in wired/wireless networks without compromizing TCP-friendliness in both wired and wireless environments.     

Advocating a Remote Socket Architecture for Internet Access Using Wireless LANs

One challenge in the development of telecommunication networks is the seamless integration of wireless devices into the global Internet. Although it is well known that the Internet protocols were designed for heterogeneous networks an end-system with the usual Internet protocol stack will suffer an inefficient communication while connected via a wireless link. The protocol mechanisms of the transport layer can lead to poor performance in case of TCP and a high loss rate in case of UDP. In this paper we advocate a Remote Socket Architecture (ReSoA) which is a kind of proxy-oriented architecture for wireless Internet access in Wireless LAN environment. This approach allows the use of a thin protocol stack on the wireless end-system to save scarce resources and a tailored protocol for the wireless link without breaking the original TCP semantics. We show the suitability of ReSoA by comparing its performance with that of pure TCP and Berkeley Snoop through actual measurements in a test environment.     

Novel Fastest Retransmission and Rate Control Schemes for Improving TCP Performance in Wireless Ad Hoc Networks

A number of different authors have considered the problem of performance degradation of transmission control protocol (TCP) in wireless ad hoc networks. We herein show that pauses in packet transmission due to packet losses are the fundamental cause of performance degradation of TCP in wireless ad hoc networks. To minimize the duration of packet transmission pauses, we propose a fast retransmission scheme for improving TCP performance in consideration of the inter-operability of previously deployed TCPs in wireless ad hoc networks. We also propose an additional rate control scheme for TCPs to reduce the probability of packet contention. Using OPNET and NS2 simulations, we show that our proposed schemes can provide a much better performance than conventional TCPs.     

改进无线网络TCP性能的研究

对采用TCP协议传输数据的实现过程及其在无线网络中可能遇到的问题进行了描述。对因无线信道误码率较高和频繁切换而导致网络性能下降的问题,提出了无线链路层快速重传技术改善网络性能的有效措施,并研究了在无线网络中链路层快速重传技术对无线TCP数据传输的影响。仿真表明链路层快速重传可以有效地改善无线TCP的性能,进一步提高了网络利用率和吞吐量。     

Design of coordinator to eliminate redundant local retransmission in wireless networks

Owing to limited bandwidth, high bit error rate, and bursty error in the wireless environment, the performance of the transmission control protocol (TCP) degrades greatly in wireless networks.Up to now, many researchers have contributed greatly to the wireless TCP field.However, in most of their works, the wireless TCP module usually works in the TCP layer and has no idea of the actual time of the packet transmission, which is determined by the Scheduler in the media access control (MAC) layer, and this will bring the inaccuracy to the local retransmission timeout and induce the redundant local retransmission.In this article, a coordinator is introduced into the base-station (BS), which can provide efficient cooperation between the TCP module and the scheduler module.On the bais of the performance analysis and simulation results, the proposed method is shown to eliminate redundant local retransmission, increase throughput, and improve TCP-level fairness in wireless networks.Moreover, this scheme is orthogonal to those existing wireless TCP schemes, thus it can give great compatibility to the current networks, and further enhance the performance of TCP under the condition that the performance improvement benefiting from the existing approaches will not be affected.     

TCP Window Control for Variable Bandwidth in Wireless Cellular Networks

Most of TCP schemes in wireless networks assume that the bandwidth of the bottleneck link remains constant over time. However, in wireless cellular networks, to effectively manage the limited resources, the bandwidth is controlled based on radio condition over time. Such varying bandwidth can cause the networks congestion or underutilization. In this letter, we propose a new window control algorithm to improve TCP performance in wireless cellular networks with variable bandwidth. Simulation results illustrate that our proposal improves the performance of TCP in terms of fairness and link utilization     

Improving TCP/IP Performance over Third-Generation Wireless Networks

As third-generation (3G) wireless networks with high data rate get widely deployed, optimizing the transmission control protocol (TCP) performance over these networks would have a broad and significant impact on data application performance. In this paper, we make two main contributions. First, one of the biggest challenges in optimizing the TCP performance over the 3G wireless networks is adapting to the significant delay and rate variations over the wireless channel. We present window regulator algorithms that use the receiver window field in the acknowledgment (ACK) packets to convey the instantaneous wireless channel conditions to the TCP source and an ACK buffer to absorb the channel variations, thereby maximizing long-lived TCP performance. It improves the performance of TCP selective ACK (SACK) by up to 100 percent over a simple drop-tail policy, with small buffer sizes at the congested router. Second, we present a wireless channel and TCP-aware scheduling and buffer sharing algorithm that reduces the latency of short flows while still exploiting user diversity for a wide range of user and traffic mix.     

全IP蜂窝通信系统TCP性能的改进

在无线网络中,造成丢包的主要原因是无线链路的高误码率(BER)及主机在区域间移动。如果TCP的丢包处理简单采用启动拥塞控制机制,势必导致网络传输性能恶化。本文以全IP蜂窝通信系统为例,概述TCP/IP协议组用于无线链路的性能问题,提出解决这些问题的方案,分析该方案的优点和局限性。     

TCP Throughput Enhancement over Wireless Mesh Networks

TCP is the predominant technology used on the Internet to support upper layer applications with reliable data transfer and congestion control services. Furthermore, it is expected that traditional TCP applications (e.g., Internet access) will continue to constitute the major traffic component during the initial deployment of wireless mesh networks. However, TCP is known for its poor throughput performance in wireless multihop transmission environments. For this article, we conducted simulations to examine the impact of two channel interference problems, the hidden terminal and exposed terminal, on TCP transmissions over wireless mesh networks. We also propose a multichannel assignment algorithm for constructing a wireless mesh network that satisfies the spatial channel reuse property and eliminates the hidden terminal problem. The simulation results demonstrate the effectiveness of the proposed approach in improving the performance of TCP in wireless multihop networks.     

Modelling of wireless TCP for short‐lived flows

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.