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.

TCP/IP与ATM的互联及网关功能的实现

人们在工作、学习和生活中提出了更多的通信业务,如高清晰度电视、电视会议、可视电话、点播电视等。对这些多功能化的需求,现今的任何网(包括电话网、用户电报网、公用分组交换数据网、电路交换数据网、数字数据网、LAN、WAN、MAN、ISDN、CATV等)都无法完成。因此,无论从用户角度还是从网络经营者的角度,都希望建立一个单一的网络。这个网络便是B-ISDN(宽带综合业务数字网)。文中主要讨论TCP/IP与ATM的互联,以及网关如何实现TCP/IP与ATM(异步传输模式)之间的协议转换。简单介绍了ATM的概念及分层模型,给出了IP与ATM结合的多种解决方式。     

TCP/IP协议的ASIC设计与实现

文章介绍了一种TCP/IP协议族传输、处理TCP数据和IP数据报过程的ASIC设计-TCP/IP协议处理器的硬件实现。简单介绍了TCP/IP协议，着重介绍了TCP/IP协议处理器系统结构以及各模块设计。硬件实现的TCP/IP协议处理器提高了IP数据报的处理速度，更重要的是，将Internet网络数据传输从传统的依赖电子计算机系统的模式中解放出来，实现了脱离计算机系统环境建立Internet网络连接。     

嵌入式TCP/IP协议栈的设计与实现

详细描述了TCP/IP协议栈的裁剪、设计和实现方案.该协议栈以PHILIPS LPC2294微处理器、以太网控制器RTL8019AS为硬件平台,采用模块化层次化的结构设计,实现了ARP、IP、ICMP、UDP等协议模块.经过精简后的协议栈代码量小,结构合理,易于移植和扩充.     

单片机的嵌入式TCP/IP协议栈设计及其实现路径

信息技术的快速发展,为嵌入式网络实际应用范围的扩大带来了重要的保障作用.因此,本文通过对硬件平台的设计分析,对获取的可靠的单片机嵌入式TCP/IP协议栈及其实现路径,为实际问题的有效处理带来了必要的参考信息.这种系统运行中最大的特点是工作效率高、运行成本低,具有一定的市场应用前景.     

TCP/IP Performance over 3G Wireless Links with Rate and Delay Variation

Wireless link losses result in poor TCP throughput since losses are perceived as congestion by TCP, resulting in source throttling. In order to mitigate this effect, 3G wireless link designers have augmented their system with extensive local retransmission mechanisms. In addition, in order to increase throughput, intelligent channel state based scheduling have also been introduced. While these mechanisms have reduced the impact of losses on TCP throughput and improved the channel utilization, these gains have come at the expense of increased delay and rate variability. In this paper, we comprehensively evaluate the impact of variable rate and variable delay on long-lived TCP performance. We propose a model to explain and predict TCPs throughput over a link with variable rate and/or delay. We also propose a network-based solution called Ack Regulator that mitigates the effect of variable rate and/or delay without significantly increasing the round trip time, while improving TCP performance by up to 100%.     

IP Transmission over TETRA Packet Data Service: Simulation and Measurement Results

This paper evaluates the packet data performance of Internet Protocol (IP) over TErrestrial Trunked RAdio (TETRA), focusing on the effects of packet size and message transmission rate. We performed a range of simulations to evaluate the average packet delay and packet failure probability corresponding to IP datagram transmission on the Packet Data CHannel (PDCH) in a TETRA cell. We employed IP packets of different sizes and we considered a number of different scenarios with respect to the number of users in a cell and datagram transmission rate. The simulation results offer TETRA operators the means for facilitating network planning and optimization of datagram-based services. Apart from the simulation, we also conducted an extensive measurement survey on the performance of IP over the TETRA PDCH. In particular, we carried out measurements in a client–server communication scenario with different datagram sizes and typical user mobility and radio propagation conditions. Measurement results include throughput, delay jitter, percentage of lost datagrams and out-of-order datagrams. The results obtained through our measurement survey can extent and enhance the simulation results because they are more realistic and consider user mobility as well as channel impairments.

IP网络传输话音和TDM业务的新技术-TDMoIP

介绍3TDMoIP的实现过程，主要对Ingress方向的上数据处理过程进行描述，在IP网络上实现数据处理业务。与传统网络相比，IP网络组网更简单经济，传送数据、图像、声音质量更好，与VOIP相比时延更小。     

RS6000 AIX环境下TCP/IP和DNS的设置

较详细地介绍了RS6000 AIX环境下TCP/IP和DNS的设置方法.     

基于Modbus TCP/IP通信的研究与实现

Modbus TCP/IP通信协议是在TCP/IP协议栈上嵌入Modbus报文,Modbus协议与以太网的结合扩展了Modbus的应用,该协议已经成为通用的工业通信协议标准之一。现在工业控制领域基于Modbus的通信仍然以串行链路的Modbus RTU为主,所以对Modbus TCP/IP通信协议的研究与应用都非常有意义。分析Modbus TCP/IP协议的总体结构描述,介绍其客户机/服务器模型以及实现客户机/服务器的通信。     

Study of the TCP Dynamics over Wireless Networks with Micromobility Support Using the ns Simulator

Several IP micro-mobility protocols have been proposed to enhance the performance of Mobile IP in an environment with frequent handoffs. In this paper we make a detailed study of how some of these protocols namely Cellular IP, HAWAII and Hierarchical Mobile IP affect the behavior of TCP and their interaction with the MAC layer. The aim of the paper is to investigate the impact of handoffs on TCP by means of simulation traces that show the evolution of segments and acknowledgments during handoffs.     

TCP/IP和DataSocket技术在网络虚拟实验室中的应用

本文介绍了网络虚拟实验室的框架,针对复杂网络控制系统通信的不同需求,将TCP/IP和DataSocket两种网络技术有机结合、实现综合应用,提供一种基于LabWindows/CVI平台的虚拟实验室实现网络通信的方案.经过运行测试,该方案完美实现了虚拟实验室的网络化,可为网络虚拟实验室的建设提供重要借鉴.     

基于TCP/IP网络视频会议系统的研究与设计

讨论了一个基于IP的网络视频会议系统以及视频、音频子系统的设计与实现;说明了如何实现视频、音频同步;最后对系统性能进行了检测。     

基于Linux操作系统下的TCP/IP网络通信研究与应用

Linux操作系统既提供优异的网络支持,又具有非常严谨的安全体系结构,因此成为了网络通信的主要平台。随着网络的不断发展,传统的纸张式的文件传输方式已经不再适合发展的需要,人们更期待一种便捷、高效、环保、安全的传输方式。主要分析了基于Linux操作系统下利用TCP/IP协议进行网络通信的全过程,给出一种通用的基于客户机/服务器的文件传输模型,并在实践中证明了其可行性。     

基于IP over SDH河南电力调度数据网规划及互联

根据调度数据网承载信息的特点及网络安全的需要,介绍了基于IP Over SDH的河南电力调度数据网络的总体规划和调度数据网双平面、河南省电力调度通信中心接入网的网络规划和结构。对基于河南电力通信网ECI第一平面和华为(HUAWEI)第二平面的调度数据网设计要点和网络保护机制进行了理论分析。对河南电力调度数据网建设过程中骨干网协议互联以及接入网2M对接中协议设置进行了说明,为保障调度数据网的安全运行和故障分析提供了有力的依据。     

Efficiency of the GSM-GPRS Air Interface for Real-Time IP Traffic Flows With and Without Packet Dropping

One IP terminal can occupy a single slot or a multiple number of slots within time frames in the GSM and GPRS, respectively. A limited number of radio resources (slots) are allocated in a base station for such IP terminals. If one IP terminal can occupy only one slot discontinuously in a time frame, there is one possibility resorting to all IP terminals to preserve active mode at a time. Thus, the number of accepted call in the GSM is the same as that of the radio resource. Similarly, if one terminal can occupy a multiple number of slots discontinuously/dynamically in a time frame, the number of accepted calls is obtained by dividing the number of radio resources during that time by the maximum allowed number of slots per IP terminal. A burstiness factor is defined for the IP traffic over GSM-GPRS air interface. Traffic channel efficiency with a bursty real-time IP traffic is unacceptably low, especially with the range of acceptable call loss probabilities pertaining to a lower burstiness factor. The channel efficiency can be enhanced and the call loss probability can be suppressed significantly if a higher maximum number of calls is accepted. Allocated radio resources are less than the maximum number of packet transmissions at a time. Therefore, some packets could be dropped from the real-time transmission system. A complete analysis for the real-time IP packet transmission over the single slot GSM and dynamically variable multislot GPRS air interface without packet dropping, and with packet dropping that increases the channel efficiency is executed. Results show that the channel efficiency as well as the packet dropping probability increases with increasing call intensity, maximum number of admitted IP calls and the burstiness factor.     

Data traffic‐based analysis of delay and energy consumption in cognitive radio networks with and without resource reservation

A new opportunistic cross‐layer MAC protocol involving channel allocation and packet scheduling for cognitive radio networks is proposed. Cognitive radio allows secondary users (SUs) to exploit the available portions of the licensed spectrum bands without interfering with primary users. In particular, we consider a cognitive radio system, where SUs are equipped with two transceivers: a control transceiver and a software‐defined radio transceiver. Data traffic characteristics of SUs are considered to ameliorate system performance. So, we propose a mechanism of resource reservation to improve QoS requirements that favors successful SUs to transmit data during x time slots without interfering with primary users. The key novelty of this paper is giving priority for SUs with important data traffic and which frequently solicits data channels to transmit for the remaining time of the ongoing time slot and for the next time slots directly after checking the channel availability. We develop a new analytical model to evaluate delay parameter for two scenarios with and without resource reservation and we then investigate the impact of those scenarios on the energy consumption. We show through simulations that cognitive radio performances increase noticeably with the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd.     

WDM城域环网中支持可变长分组的节点结构及MAC协议设计

WDM城域环网在升级时,信道数可能是不变的.本文基于此设计了一种新颖的节点结构,它由固定发射器和一组固定接收器组成.基于该结构,文中给出了支持可变长分组的时隙结构及MAC协议.由于实现MAC协议毋需专用波长信道,提高了资源利用率.理论分析和仿真结果证明了本文设计方法可以充分利用空间重用能力,获得很好的网络流量,分组排队时延及分组丢弃率.对于信道数较多,或者网络在升级时信道数也可能变化的情况,本文建议采用固定发射器,一组"准"调谐的接收器结构.该方案可在实现复杂度,网络性能及成本间取得折衷.     

End‐to‐end security‐reliability analysis of multi‐hop cognitive relaying protocol with TAS/SC‐based primary communication,total interference constraint and asymmetric fading channels

In this paper, we analyze the tradeoff between outage probability (OP) and intercept probability (IP) for a multi‐hop relaying scheme in cognitive radio (CR) networks. In the proposed protocol, a multi‐antenna primary transmitter (PT) communicates with a multi‐antenna primary receiver (PR), using transmit antenna selection (TAS) / selection combining (SC) technique, while a secondary source attempts to transmit its data to a secondary destination via a multi‐hop approach in presence of a secondary eavesdropper. The secondary transmitters such as source and relays have to adjust their transmit power to satisfy total interference constraint given by PR. We consider an asymmetric fading channel model, where the secondary channels are Rician fading, while the remaining ones experience the Rayleigh fading. Moreover, an optimal interference allocation method is proposed to minimize OP of the primary network. For the secondary network, we derive exact expressions of end‐to‐end OP and IP which are verified by Monte Carlo simulations.