Growth trends in wide-area TCP connections

A recently completed single-site study has yielded information about how Internet traffic will evolve, as new users discover the Internet and existing users find new ways to incorporate the Internet into their work patterns. The author reviews existing statistics and studies of network growth, which show that network traffic generally grows exponentially with time, at least until the network carrying capacity is reached. He then describes how he captured and reduced the data used in this study. The following points are also addressed: the overall growth in the site's wide-area traffic; the appearance of periodic traffic; the growth in network use by individual computers or users; and the changing geographic profile of the traffic. The implications and limitations of the results are also summarizes     

A dynamic cross-layer data queue management approach based on priority for delay-tolerant mobile sensor networks

This paper presents a Dynamic Cross-layer Data Queue Management approach (DC-DQM) based on priority to address the priority deviation problem in Delay-Tolerant Mobile Sensor Networks (DT-MSNs). Receiver-driven data delivery scheme is used for fast response to data transfers, and a priority based interaction model is adopted to identify the data priority. Three interactive parameters are introduced to prioritize and dynamically manage data queue. The experimental results show that it can ameliorate data delivery ratio and achieve good performance in terms of average delay.     

Reduce delay of multipath TCP in IoT networks

Wireless Networks - Multi-homed devices such as smartphones, tablets and laptops are enabled with multiple heterogeneous interfaces available for transmission. Those interfaces can be utilized for...     

A self-tuning controller for queuing delay regulation in TCP/AQM networks

Telecommunication Systems - AQM router aims primarily to control the network congestion through marking/dropping packets which are used as congestion feedback in traffic sources to balance their...     

Directional core selection approach and dynamic tree reorganization for delay and delay variation multicast routing

Multicast communication constrained by end‐to‐end and interdestination delay variation is known as delay and delay variation–bounded multicast. These constraints are salient for real‐time multicast communications. In this paper, we propose a directional core selection algorithm for core selection and delay variation–bounded multicast tree generation. Another algorithm, based on k‐shortest paths, is proposed to further decrease the interdestination delay variation of the trees generated by directional core selection. We also propose the dynamic version of both algorithms that respond to dynamic join and leave requests to the ongoing multicast session by reorganizing the tree and avoiding session disruption. Simulations show that the proposed algorithms surpass existing algorithms in end‐to‐end delay, interdestination delay variation, execution time, and failure probability.     

Mean delay in synchronous packet networks with priority queueingdisciplines

A Markov model which approximates the behavior of networks that transport messages of varying priority classes is developed. The model is shown to accurately predict behavior for a tandem network with departures and an unidirectional loop network. In the cases which required approximation, the model was validated by performing extensive computer simulation and comparing it with analytical results     

Profiling and reducing processing overheads in TCP/IP

This paper presents detailed measurements of processing overheads for the Ultrix 4.2a implementation of TCP/IP network software running on a DECstation 5000/200. The performance results were used to uncover throughput and latency bottlenecks. We present a scheme for improving throughput when sending large messages by avoiding most checksum computations in a relatively safe manner. We also show that for the implementation we studied, reducing latency (when sending small messages) is a more difficult problem because processing overheads are spread over many operations; gaining a significant savings would require the optimization of many different mechanisms. This is especially important because, when processing a realistic workload, we have found that nondata-touching operations consume more time in aggregate than data-touching operations     

A semistate approach to feedback stabilization of neutral delay systems

In this paper we consider derivative feedback in a semistate framework for the problem of stabilizing the neutral root chains for a class of neutral delay-differential equations where the difference operator (orD-operator) is unstable. Recent work has shown that such systems cannot be stabilized by state feedback alone[3], [13], [16]. In addition, we consider the problem of using derivative feedback to eliminate all neutral root chains entirely, thus turning the closed loop system into a retarded delay system. By representing neutral delay-differential systems as semistate systems over a polynomial ring of delay operators, both of the above problems are shown to be reducible to the following question: Given matricesD,B over a commutative ringR, when does there exist a matrixM also overR such thatD+BM isR-unimodular? In the case of commensurable point delays our results are applications of some recent results on the simultaneous stabilization problem [19], and we give a constructive procedure for computing the required feedback law. In the case of noncommensurable delays we give a sufficient condition for the existence of suitable feedback for the above problems.     

Improving throughput of long-hop TCP connections in IP over OPS networks

Optical Packet Switching (OPS) can provide the ever-increasing bandwidth required for Internet traffic and new applications for future networks. However, optical packet loss is the major problem for an OPS network. Moreover, by increasing the number of hops between a pair of ingress–egress switches in an OPS network, optical Packet Loss Rate (PLR) between this pair is increased. Therefore, due to a higher PLR for long-hop TCP connections, the throughput of these connections may be much lower than the short-hop TCP connections. To overcome this problem, it is proposed in this paper to use the retransmission idea in the optical domain not only to increase TCP throughput but also to improve the throughput of multi-hop TCP connections, and also to have a loss-free OPS network. Under retransmission in the optical domain, a copy of the transmitted traffic is kept in the electronic buffers of ingress switches and retransmitted in the optical domain whenever required. Note that the TCP layer has its own retransmission at the client packet level as well. By retransmission of lost packets in the optical domain, TCP would be unaware of the lost client packets, and therefore, TCP would not reduce its sending rate. In this paper, TCP throughput is studied in a bufferless slotted OPS network and the effectiveness of the proposed mechanism is evaluated.

An early implementation of a DAVIC V1.0 system — use of dynamic connections for interactive multimedia services

Advances in networking technology and the provision of greater wide area bandwidths are the catalysts for the emergence of new broadband services in both the business and residential market. This is in turn producing new, more complex, business models involving service consumers, content providers, service brokers and network connectivity providers. Such business models require the underlying technology to enable sophisticated network signalling to set up, monitor and tear down connections reliably and in real time.This paper describes the evolution of a broadband call control demonstrator believed to be the first of its kind in the world to provide a practical realisation of the signalling required in such business models. It focuses on signalling and switch control and has developed into an end-to-end implementation of a Digital Audio Visual Council (DAVIC) V1.0 system.The evolution of the switch control and signalling architecture is described, showing where existing standards have been implemented to provide basic connectivity across an ATM network. Additional capabilities are built upon this platform through the adoption of emerging signalling concepts, such as session control, and application control using distributed object-oriented principles, for the access and control of a video-on-demand service.To further understand the evolutionary path for emerging consumer systems, the paper illustrates how work was undertaken to separate set-top box (STB) functionality into a set-top unit (STU) and a network interface unit (NIU), allowing easier access to future broadband network capabilities.     

一种减少移动IPv6切换延时的新方法

切换问题是移动计算环境中最基本的问题。理想的切换是指同时具备快速切换和平滑切换能力的无缝切换;快速切换就是要求系统具有最小的切换时延,平滑切换则要求系统具备最低的丢包率。现提出一种基于组播的平滑切换框架模型,该模型的基本思想是让移动节点本身携带途经的接入路由器绑定更新队列,每当移动节点到达一个新的链路并获得该链路的转交地址,就向家乡代理和队列成员进行组播。该模型有效地减少了数据包的丢失率,减少了延时,并与现有的快速切换/IPv6路由优化技术能很好地结合起来。     

A filtering approach for reducing timing jitter due to the acousticeffect

We introduce a signal processing approach to compensate for the timing jitter produced by the acoustic effect in soliton communications. The other main sources of timing jitter, the Gordon-Haus effect and the polarization effect, are inherently stochastic. By contrast, the acoustic effect is deterministic and becomes the dominant source of bit error rates in standard soliton systems when the bit rates are more than 10 Gb/s and the transmission distance is more than several thousand kilometers. We exploit the deterministic nature of the acoustic effect to introduce a scheme that predicts the amount of timing jitter as a function of the previous transmitted bits and uses the information to adjust the sampling period of the received soliton pulses. We demonstrate successful application of the scheme by simulations and discuss implementation issues     

WLAN中TCP性能改进的跨层方案仿真

随着无线网络的迅速发展,如何改进TCP在无线网络中的传输性能这一课题,已经成为国内外研究的热点.文章分析了现有的几种典型的TCP改进方案,并在此基础上介绍一种新的跨层方案.通过在传输层和链路层之间引入ARQ Snoop代理,在链路层检测并重传ARQ分组的同时,协调WLAN MAC子层的ARQ机制与TCP的ARQ策略.     

A systematic approach to reducing angular color shift in cavity-based organic light-emitting diodes

The white angular dependence (WAD) is considered a serious problem in top emitting OLEDs (TOLEDs), both in monochrome and multi-color subpixel configurations. This work aims at providing a systematic strategy for obtaining WAD-free performance with little compromise in efficiency in TOLED-based multi-color displays. Starting with a slightly blue-detuned microcavity structure leading to low WAD per individual primary colors, we try to look for a condition where angular intensity drop rates are well balanced among the subpixels involved and yet the efficiency can be maintained within a certain threshold value. With the proposed protocol, red, green and blue TOLEDs are demonstrated that show a very low angular color shift of 2.4 “just noticeable color difference” (JNCD), 1.7 JNCD, and 1.4 JNCD for red, green, and blue devices themselves and 1.4 JNCD for a 1:1:1 mixture of red, green and blue. These devices are shown to exhibit not only low WAD but also high efficiency that is still within 70% of the maximum achievable values.     

A dynamic approach to controlling high-level synthesis CAD tools

In this paper, we present a novel model of CAD tool control that can be used in the constraint-directed control of high-level synthesis tools. To enable this control we introduce the concept of a design space reasoning mechanism. We formally describe a statistical based, machine learning process that automatically generates the tool control knowledge necessary to drive the design space reasoning mechanism. The representation of this tool control knowledge in the form of a fuzzy, linear differential, qualitative model is described. Finally, the experimental results obtained using the Magellan system are presented     

A novel two-step approach to restorable dynamic QoS routing

Aiming at minimizing the combined bandwidth cost of a pair of disjoint active and backup paths, a popular approach to designing restorable dynamic quality of service (QoS) routing schemes is based on the integer linear programming (ILP) formulation. Owing to the very different natures of active and backup paths, we found this approach problematic. In this paper, we propose an alternative approach, called two-step restorable QoS routing. In the first step, an active path is found using the widest shortest path (WSP) routing. In the second step, the corresponding backup path is determined using one of the three variants of shortest widest path (SWP) routing: basic SWP, approximate SWP or composite SWP. Combining the two steps, three novel two-step routing algorithms, denoted by SBW, SAW, and SCW, are obtained. Comparing with the best known algorithms, we show that our two-step routing approach yields noticeably lower call blocking probability, shorter active-path length, and additional flexibility of adjusting backup-path length (depending on the SWP variant adopted). Besides, our two-step routing approach gives a much shorter running time than the ILP approach, which makes it more suitable for dynamic routing.     

A doubly adaptive approach to dynamic MRI sequence estimation

Dynamic magnetic resonance imaging (MRI) refers to the acquisition of a sequence of MRI images to monitor temporal changes in tissue structure. We present a method for the estimation of dynamic MRI sequences based on two complimentary strategies: an adaptive framework for the estimation of the MRI images themselves, and an adaptive method to tailor the MRI system excitations for each data acquisition. We refer to this method as the doubly adaptive temporal update method (DATUM) for dynamic MRI. Analysis of the adaptive image estimate framework shows that calculating the optimal system excitations for each new image requires complete knowledge of the next image in the sequence. Since this is not realizable, we introduce a linear predictor to aid in determining appropriate excitations. Simulated examples using real MRI data are included to illustrate that the doubly adaptive strategy can provide estimates with lower steady state error than previously proposed methods and also the ability to recover from dramatic changes in the image sequence.     

A neural network approach to fluid quantity measurement in dynamic environments

Sloshing causes liquid to fluctuate, making accurate level readings difficult to obtain. In this paper, a measurement system has been described that can accurately determine fluid quantity in the presence of slosh. The measurement system uses a single-tube capacitive sensor to obtain instantaneous level of the fluid surface. A neural network based classification technique has been applied to predict the actual quantity of the fluid under sloshing conditions. Effects of temperature variations and contamination on the capacitive sensor have been discussed and it is proposed that these effects can also be eliminated with the proposed neural network based classification system. To examine the performance of the classification system, many field trials were carried out on a running vehicle at various tank volume levels that range from 5 L to 50 L. The paper also investigates the effectiveness of signal enhancement on the neural network based signal classification system. Signal enhancement is performed using selected signal smoothing functions such Moving Mean, Moving Median, and Wavelet filters. Results obtained from the investigation are compared with traditionally used statistical averaging methods, and it proved that the neural network based measurement system can produce highly accurate fluid quantity measurements in a dynamic environment. The approach demonstrated herein will enable a wide range of fluid quantity measurement applications in the fields of automotive, naval and aviation industries to produce accurate fluid level readings.     

An interactive and team approach to multimedia design curriculum

Over the past decade, increasingly powerful technologies have made it easier to compress, distribute, and store multimedia content. The merger of computing and communications has created a ubiquitous infrastructure that brings digital multimedia closer to the users and opens up tremendous educational and commercial opportunities in multimedia content creation, delivery, rendering, and archiving for millions of users worldwide. Multimedia has become a basic skill demanded by an increasing number of potential jobs for electrical engineering/computer science graduates. In this article, the authors intend to share their experiences and new ways of thinking about curriculum development. It is beneficial for colleagues in the multimedia signal processing areas for use in developing or revising the curriculum to fit the needs and resources of their own programs.     

一种基于无线TCP时延的互联网业务问题定界和优化的方法

为提升用户互联网业务感知、缩短建立时延,本文提出了一种基于TCP建立时延的跨层优化方法。通过对协议的研究,将TCP建立时延拆解为无线TCP时延与核心TCP时延两个独立过程。以某省TCP业务为样本,通过多项式回归算法得到无线TCP时延与用户数的函数关系式,论证了在用户数小于200个且网络性能稳定时,无线TCP时延与等待调度时间强相关、与业务类型无关。本文通过定量分析、建模仿真和现网验证,完成了TCP建立时延拆分和感知问题定界,得到了无线TCP时延在无线资源管理机制下的SR调度数据量、DRX Inactive Timer和IBLER的最优配置策略,具有较高的实践价值。