TCP Communication Research Articles

An Implementation Design of a WLAN Handover Method Based on Cross-Layer Collaboration for TCP Communication

An Implementation Design of a WLAN Handover Method Based on Cross-Layer Collaboration for TCP Communication

Research of Stand-Alone Photovoltaic Power Generator Monitoring System

To design and implement a stand-alone photovoltaic power generator monitoring system with remote control functions. The hardware architecture consists of solar cells, solar charger, DC/AC inverter, energy storage device, energy consumption equipment, electrical load, PLC controller, I/O card, router, and supervisory control computer, while the software is composed of programmable software and graphic supervisory control software. With the self-developed solar charger, the conversion efficiency of this system achieves 93.26%. Besides, with maximum power point tracking function, the solar cells could continuously output maximum power. The user-friendly human-machine interface would transmit the information acquired by PLC controller, through MODBUS TCP communications protocol, to the remote computer; this would supervise and control the voltage, electric current, power, fault detection, network monitoring, and run chart function in the photovoltaic energy generating system; and the supervised and controlled data would be recorded in detail and stored into the database for further study and analyses. The experiment confirms the convenient operation of this system that it could effectively supervise and control the conditions of the system.

An efficient handover decision method based on frame retransmission and data rate for multi-rate WLANs

To enhance the communication performance at handover between multi-rate WLANs, we propose a new handover decision method that can be applied to our previously reported handover management scheme, which handled a handover by utilizing two WLAN interfaces (IFs) through cross-layer collaboration between layer 2 and layer 4. It should be noted that we here propose a new handover decision scheme for traversing between multi-rate WLANs, while our previous decision scheme works only in fixed-rate WLANs. In this paper, to treat a handover between multi-rate WLANs, we employ two kinds of information: (1) the most frequently used data rate (MFDR) for assessing the stable communication performance of a multi-rate WLAN, and (2) the frame retransmission ratio (FRR) for assessing its exact communication performance. The MFDR enables us to estimate the area where we should start handover. If the MFDRs of two interfaces are same in the area, the FRR allows us to compare the wireless condition on the two interfaces precisely to give an optimal handover point. Through simulation experiments, we show that our proposed scheme certainly estimates an appropriate handover point as a result of multi-path transmission (s), thereby providing handover successfully. That is, the proposed method can determine handover at an optimal point depending on the various distances between access points, the mobile node (MN) velocity, and the MN moving pattern. Moreover, our proposed scheme prevents the redundant network load caused by multi-path transmission as much as possible, thereby providing the ideal TCP communication performance.

Review on Attack and Defense in Tor

Tor is currently the most famous tool of anonymous TCP communications for clients who need security, privacy and anonymity in their low-latency communications over the public network such as Internet. For this purpose, Tor provides reliable ways of communication through randomly selecting relay network circuits on client’s request to offer a secure communication path. However, several research papers are available which identify weaknesses of Tor that attackers can exploit to reveal a client’s identity. This paper highlights a few such Tor’s weaknesses through which attackers can launch snooping attacks on Tor. Some major attacks are discussed and it is observed that most attacks are launched at application-level protocols such as HTTP after compromising exit node or both entry and exit nodes of Tor relay circuits. Countermeasures against such attacks are also identified to increase security and anonymity over Tor based communications.

Adaptive active queue management controller for TCP communication networks using PSO-RBF models

Addressing performance degradations in end-to-end congestion control has been one of the most active research areas in the last decade. Active queue management (AQM) aims to improve the overall network throughput, while providing lower delay and reduce packet loss and improving network. The basic idea is to actively trigger packet dropping (or marking provided by explicit congestion notification (ECN)) before buffer overflow. Radial bias function (RBF)-based AQM controller is proposed in this paper. RBF controller is suitable as an AQM scheme to control congestion in TCP communication networks since it is nonlinear. Particle swarm optimization (PSO) algorithm is also employed to derive RBF parameters such that the integrated-absolute error (IAE) is minimized. Furthermore, in order to improve the robustness of RBF controller, an error-integral term is added to RBF equation. The results of the comparison with Drop Tail, adaptive random early detection (ARED), random exponential marking (REM), and proportional-integral (PI) controllers are presented. Integral-RBF has better performance not only in comparison with RBF but also with ARED, REM and PI controllers in the case of link utilization while packet loss rate is small.

Traffic monitoring in transmission control protocol/active queue management networks through a time-delay observer

The use of the control theory tools for traffic control in communication networks, for example, the congestion control in internet protocol (IP) routers, has given rise to challenging issues in the time-delay system framework. In this study, the authors propose to design a linear time-delay observer for traffic monitoring in transmission control protocol/active queue management (TCP/AQM) networks. More precisely, the authors focus on a bottleneck topology consisting of long-lived TCP communications through a router. The developed mechanism, located at the router, aims at supervising the network via TCP flow estimations as well as detecting a class of anomalies. This issue is formulated as a stability problem for multiple delayed systems and appropriate robust control tools such as quadratic separation are adopted to address it. Then, some simulations via the network simulator NS-2 and an emulation experiment support the proposed methodology.

Incorporating MIP and SIP for Cross-Layer Fast Handoff in IPv6 Networks

Mobile IP and SIP are well-known approaches to support mobility. However, the triangular routing involved in Mobile IP makes it unsuitable for real-time RTP/UDP multimedia traffic, and SIP may cause the disconnect of ongoing TCP communications. To provide a cross-layer fast handoff in an IPv6 network, we propose incorporating both approaches to address different transport protocols. Because movement detection and IP address acquisition are the most time-consuming tasks during handoff, the proposed scheme utilizes a link-layer trigger and IP address pre-allocation to achieve fast handoff. It also takes into account the projected path of the mobile node. The experimental results show that for SIP mobility, handoff latency of the proposed scheme is 353.7 ms, less than one-fourth the 1596.7 ms of the original scheme. For Mobile IPv6, handoff latency of the proposed scheme is 1014.2 ms, just over one-half the 2011.2 ms of the original scheme. The average handoff frequency improvement in the scenarios of moving randomly and moving straight are 3% and 27%, respectively. This indicates that the proposed scheme can effectively reduce not only handoff latency but handoff frequency.

Measurement of TCP computational and communication energy cost in MANETs

TCP suffers dramatically when implemented within wireless multi-hop ad-hoc networks due to its specific characteristics (e.g. mobility and being battery dependant). Being battery operated, ad-hoc network nodes have to be energy conservative. Many researches investigated the performance of TCP in terms of throughput and/or energy consumption. Energy consumption studies, however, were only partial. This paper introduces complete, detailed measurements of TCP’s energy consumption resulting from both communication and computational energy costs. Our measurements are realized using a hybrid approach, combining simulations and realistic test-bed configuration. Our study is conducted taking into account different TCP variants facing various data loss situations within the network. The obtained results show the impact of TCP’s congestion control algorithm on TCP’s energy cost.

Wireless loss-tolerant congestion control protocol based on dynamic aimd theory

Recently, the use of Internet Protocol has rapidly expanded beyond the Internet, as evidenced, for example, by the construction of the next-generation network, empowering telecommunication networks by IP. A huge IP network is expected to emerge in the near future by means of convergence of various networks. However, Transmission Control Protocol, the de facto standard transport layer protocol providing reliable communication over such IP networks, poses several significant performance issues. The small buffer problem, unfair bandwidth allocation, and throughput degradation in wireless environments have been widely known issues in TCP communications. In this article we examine the causes of these problems from the viewpoint of window control theory. While TCP employs additive-increase multiplicative-decrease theory as a window control policy, the lack of flexibility of its static AIMD control is the basic cause for its performance degradation. After briefly reviewing TCP enhancements that utilize various modified AIMD control schemes, we introduce explicitly synchronized TCP, which employs a dynamic AIMD window control mechanism by employing feedback information from network nodes. By dynamically controlling AIMD procedures according to varying network conditions, ESTCP is able to achieve high performance even in hybrid wired/wireless networks.

A Unified Handover Management Scheme Based on Frame Retransmissions for TCP over WLANs

In ubiquitous networks based on Wireless Local Area Networks (WLANs) with limited individual coverage, mobile nodes will be likely to traverse different WLANs during TCP communication. An effective handover management scheme for achieving seamless and efficient communication throughout the handover operation is therefore crucial. To achieve this, the following three requirements are essential: (i) early initiation of handover, (ii) elimination of communication interruption upon handover, (iii) selection of an optimal WLAN. The handover scheme proposed in this study employs frame retransmission over WLAN as an indicator of link degradation, and a handover manager (HM) on the transport layer obtains the number of frame retransmissions on the MAC layer using a cross-layer architecture in order to achieve (i) and (iii). Then, it also employs multi-homing in order to achieve (ii). Simulations demonstrate that the proposed scheme can satisfy all of the three requirements and is capable of maintaining TCP performance throughout the handover operation.

GA-based PID active queue management control design for a class of TCP communication networks

Active queue management (AQM) is a key congestion control scheme for reducing packet loss and improving network utilization in TCP/IP networks. This paper proposes a proportional–integral-derivative (PID) controller as an active queue manager for Internet routers. Due to the limitations of packet-dropping probability and the effects of propagation delays in TCP networks, the TCP AQM network was modeled as a time-delayed system with a saturated input. An improved genetic algorithm is employed to derive optimal or near optimal PID controller gains such that a performance index of integrated-absolute error (IAE) is minimized, and thereby a stable queue length, low packet loss, and high link utilization for TCP networks are guaranteed. The performance of the proposed control scheme is evaluated in various network scenarios via a series of numerical simulations.

Deployable multipath communication scheme with sufficient performance data distribution method

Multi-homed environments are increasingly common, especially for mobile users. And several multipath communication techniques have been proposed, such as multipath TCP communication techniques. Multipath TCP techniques have potential to fully utilize multiple paths, but, these methods have difficulties in implementation and deployment, because users need to modify their applications or operating system or both. In this paper, we propose simple multipath communication technique, which we call Arrival-Time matching Load-Balancing (ATLB). ATLB is designed to be easily implementable on several environments. Besides, we also introduce overlay network approach which implicitly provides parallel data transfer scheme to users. The ATLB continuously calculates transmission delays of each path, including TCP queuing delay at a sender and network delay, and then sends a data segment through the TCP connection with the lowest delay. Simulation results show that ATLB realizes sufficient performance even in heterogeneous environments where the quality of paths differs. Measurement results over our wireless LAN test-bed system suggest that ATLB can fully utilize the aggregate available bandwidth over unstable multiple wireless links.

Active queue management controller design for TCP communication networks: Variable structure control approach

On the basis of variable structure control (VSC), an active queue management (AQM) controller is presented for a class of TCP communication networks. In the TCP/IP networks, the packet drop probability is limited between 0 and 1. Therefore, we modeled TCP/AQM as a rate-based non-linear system with a saturated input. The objective of the VSC-based AQM controller is to achieve the desired queue size and to guarantee the asymptotic stability of the closed-loop TCP non-linear system with saturated input. The performance and effectiveness of the proposed control law are then validated for different network scenarios through numerical simulations in both MATLAB and Network Simulator-2 (NS-2). Both sets of simulation results have confirmed that the proposed scheme outperforms other AQM schemes.

A Cross-Layer Retransmission Control for Improving TCP Performance in Wireless LAN

In this paper we propose a cross-layer retransmission control for TCP communication over a wireless link. With our proposed control, a retransmission delay for lost packet is reduced, packet losses in the wireless link are eliminated and all packets are delivered in the correct order. No change is required to TCP itself or to the sender. Our proposed method is implemented in a queue between the media access control (MAC) layer and logical link layer in a base station, and is designed to assist local retransmission control in the MAC layer. Computer simulations show that our proposed method can maximally use the bandwidth of the wireless link under high bit error rates conditions with conventional TCP control. The fairness problem of TCP communication between connections with different bit error rates in a wireless link is also improved, and MAC level fairness is also controllable.

Design of robust active queue management controllers for a class of TCP communication networks

This paper describes the design of active queue management (AQM) controllers for a class of TCP communication networks. In TCP/IP networks, the packet-dropping probability function is considered as a control input. Therefore, a TCP AQM controller was modeled as a time-delayed system with a saturated input. The objective of the work described here was to design robust controllers capable of achieving the desired queue size and guaranteeing asymptotic stability of the operating point. To achieve this aim, we have proposed two control strategies, namely a static state feedback controller and an observer-based controller. By applying the Lyapunov–Krasovskii functional approach and the linear matrix inequality technique, control laws and delay-independent stability criteria for the AQM controllers were derived. The performance of the two control schemes was evaluated in various network scenarios via a series of numerical simulations. The simulation results confirm that the proposed schemes outperform other AQM schemes.

Congestion control with multiple congestion control policy for large bandwidth‐delay‐product networks

AbstractRecently, broadband applications such as data grids and IP‐Storage Area Network have been proliferating. In these applications it is necessary to exchange large amounts of data quickly over networks with a capacity of several gigabits per second. For this purpose, various kinds of congestion control have been proposed for use in such broadband networks. In these kinds of congestion control, the idle bandwidth of the network can be used quickly by increasing the communications speed at the time of communications. On the other hand, complicated forms of congestion are generated in the network. Therefore, when these kinds of congestion control and the existing TCP communications coexist, the existing TCP communication is strongly compressed. In the present paper, TCP with multiple congestion control policies (TCP‐MP) is proposed in order to make swift use of idle bandwidths in the network. In TCP‐MP, an additional congestion control policy is provided in addition to using a form of congestion control similar to that in conventional TCP, so that information on the variation of the RTT between the transmitter and the receiver can be used to estimate the idle bandwidth of the network and the communications speed is chosen in such a way that the idle bandwidth is used up. Hence, it is possible to quickly use the bandwidth of the network within the range in which the existing TCP communications is compressed. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(1): 45–57, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20310

An Adaptive Traffic Load Balancing Method for Multi-Hop Mesh Networks in Broadband Fixed Wireless Access Systems

Broadband fixed wireless access (BFWA) systems with multi-hop mesh topologies have attracted considerable attention as a promising technology for next generation, high quality, high capacity, and high density access infrastructures. The primary advantages of mesh network topologies are an improvement of capacity by means of traffic engineering throughout the networks. This paper discusses an adaptive traffic load balancing method that maximizes the capacity for the mesh BFWA networks. Taking into account the variation of network conditions such as traffic demand distributions and qualities of wireless links, the adaptive traffic load balancing method attempts to equalize the utilization of capacity for each wireless link. To avoid deteriorating the performance of TCP communications, the proposed method implements flow-based traffic load balancing. Performance of the proposed adaptive traffic load balancing method is demonstrated and validated using the experimental mesh network environments with wired networks with up to sixteen nodes that emulates the variation of the wireless link capacity.

Compact equation of TCP throughput estimation at upgrading bottleneck link speed

AbstractThis paper considers a network in which one of the links is the bottleneck of communication, and the speed of that link is upgraded. A simple method of calculation is proposed for the effect of the upgrading on the throughput of the TCP communication passing through the link. As the first step, a formula for the TCP communication throughput is proposed, which is a function of the mean window size of the TCP flow control, the round‐trip time, and the loss ratio of the packet. The waiting time in the router, which is the major factor determining the round‐trip time, is approximated by the M/M/1/m queue. By combining those two expressions, the change of the throughput by upgrading the link speed is calculated. In order to verify the validity of the throughput calculation and the router model, the change of the TCP communication throughput in upgrading the speed of the bottleneck link is calculated, and the result is compared to the result of actual measurement in the experimental network composed of PPP and Ethernet. It is seen that the model proposed in this paper agrees well with the actual measurement although it is simple. The method is applied to the network between Mie University and SINET. The effect of the link speed upgrading on TCP throughput is examined and verified. The result obtained in this paper is expected to be useful in the network design, in estimating the link speed required in dissolving the bottleneck. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(1): 65–73, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1147

REAL-TIME INTERACTION OVER THE INTERNET

This paper describes the challenges to meet in order to enable effective real-time interaction over the Internet for the remote prototyping of automatic control solutions. The type of real-time interaction required for such a prototyping is the ability for an operator to adjust remotely the settings of a controlled system and to observe immediately the effects of this action on its dynamics. Solutions are proposed to keep a seamless degree of interactivity despite the Internet bandwidth variations. These solutions rely on an end-to-end adaptation scheme of the transmitted content. This scheme mimics the TCP communication protocol without showing the same drawbacks.

Effects on TCP of routing strategies in satellite constellations

A broadband satellite network uses a constellation of a number of similar satellites to provide wireless networking services to the Earth. A number of these constellation networks are under development. This article introduces the types of satellite constellation networks, and examines how overall performance of TCP communications carried across such a network can be affected by the choice of routing strategies used within the network. Constellations utilizing direct intersatellite links are capable of using multiple paths between satellites simultaneously as a strategy to spread network load. This allows more general routing strategies than shortest-path routing, but we show these strategies to be detrimental to the performance of individual TCP connections.