基于骨干网上行流量深度报文检测的网络质差评估方法

文章介绍通过基于骨干网上行流量深度报文检测(Deep Packet Inspect,DPI)的网速慢评估方法。DPI包含了报文信息的七层解析,也就包含了TCP协议的四层交互信息。TCP连接建立异常、TCP交互重传或者乱序的统计量都能表征网络质量情况。但对于运营商骨干网来说,上下行流量特别大,特别是下行流量,因此,运营商也只能存储上行若干TCP端口流量。由于缺乏双向TCP流量特征,网络质量异常很难精准发现。文章通过研究骨干网上行流量HTTP/HTTPS端口与用户申告网速慢的关联关系,提出骨干网上行流量特征的生成方法及网络质差评估方法。     

一种基于链路带宽估计的无线TCP改进算法

本文提出了一种能够通过带宽估计来判断无线链路报文段丢失原因,并采取相应拥塞控制机制的无线TCP算法-TCP_LD(TCP Loss Detection).文章采用Padhye模型的建模方法,推导了TCP_LD的稳态流量模型.理论分析和仿真结果说明,TCP_LD能够有效的区分出发生报文段丢失的原因,即拥塞丢失或者链路突发差错,从而提高系统的流量.     

一种高效的TCP会话数据流重组算法及应用

在网络行为管理系统中,当数据包以TCP流方式在网络上传输时,传统的基于数据包的模式匹配算法已无法满足需要.对此提出了一种高效的TCP会话数据流重组算法,详细论述了多连接管理、重复报文处理以及无序报文处理等重组过程中出现问题的解决方法,并利用此算法实现了FTP协议数据包的截获与分析.通过与Libnids库相比较,试验结果表明,该算法更具效率和稳定性.     

基于IP城域网的通信运营商DPI系统浅析

深度报文检测(DPI,Deep Packet Inspection)技术是一种基于网络数据包的应用层(OSI 7层协议的最上层)流量检测和控制技术,通过深度检测和分析网络数据包载荷的内容来对应用层信息进行重组,从而得到整个数据流或数据包的应用层信息,然后按照系统定义的策略对流量进行统计分析和控制。     

Analysis and Realization of Message Integrity Services in SSL Recording Layer

SSL记录层协议建立在可靠连接TCP之上,为上层提供机密性和消息完整性服务.介绍了SSL记录层协议的工作原理,分析描述消息完整性服务的整体机制,并利用散列算法实现.利用在MD5的基础上构造的MAC算法,防止消息被篡改,利用MAC中的序列号防止消息遭受到重放攻击和再排序攻击.全面阐述了消息完整性服务在SSL记录层上的实现.     

消息完整性服务在SSL记录层的实现分析

SSL记录层协议建立在可靠连接TCP之上,为上层提供机密性和消息完整性服务。介绍了SSL记录层协议的工作原理,分析描述消息完整性服务的整体机制,并利用散列算法实现。利用在MD5的基础上构造的MAC算法,防止消息被篡改,利用MAC中的序列号防止消息遭受到重放攻击和再排序攻击。全面阐述了消息完整性服务在SSL记录层上的实现。     

基于自动机的TCP流识别算法

为提升网络流识别性能,本文提出了一种TCP流识别算法.该算法基于传输控制协议(Transmission Control Protocol,TCP)下网络通信双方的交互过程构建双向流自动机,由该自动机根据TCP协议规则和网络流当前状态判断TCP流终止,同时以基于规则的过滤机制和超时策略为辅助措施,快速识别单包流和异常中断流.该算法内存开销、计算和内存总开销均低于经典算法固定超时策略(Fixed Timeout strategy,FT)和同类代表性算法两层自适应超时策略(Two-level Self-Adaptive Timeout,TSAT),同时该算法精度高于TSAT,且仅比默认精度标准略有下降.该算法基于协议规则识别TCP流,既保证了流的准确性,又节省了流的超时等待时间,而且算法尤其适合中流、小流和不规则TCP流比重较大的情况,使得识别系统在面临DDoS攻击、蠕虫爆发等网络异常时仍能正常运行.     

卫星TCP/ATM传输中的明确窗口指示拥塞控制策略研究

卫星ATM是近年来卫星通信领域的一个研究热点,TCP业务在卫星ATM中的传输是其中一个重要的研究课题.由于在TCP协议中主要是通过对窗口的控制来实现拥塞控制,而卫星信道传输的长延时特性大大降低了TCP层拥塞控制的效率.本文提出一种基于UBR传输的明确窗口指示拥塞控制策略,仿真结果表明在效率、公平性、VBR背景传输下的性能等各方面,取得了比目前广泛使用的Reno TCP更好的结果.并且该算法实现简单,交换机实现零信元丢失的缓冲区很小并且与TCP源连接的数目无关.     

Ad Hoc网络中的TCP不稳定性分析与改善

文章介绍了基于802.11的Ad Hoc多跳网络存在的隐藏节点问题,应用ns2仿真分析了由隐藏节点等导致的TCP不稳定性现象,并提出了TCP参数优化法和MAC层协议优化来改善不稳定性,在MAC层协议优化工作方面提出了一种新的方案-DWDB算法,对基本802.11 MAC协议进行了退避算法和重传机制的修改.仿真结果表明该方案能够在提高Ad Hoc网络吞吐性能的基础上,有效地解决不稳定性问题.     

卫星网络中的TCP协议分析

TCP协议是一个面向连接的传输协议,由于它是基于不可靠的IP服务来提供可靠的数据传输,因此,TCP必须采用端对端的流量控制、拥塞控制和差错控制机制来保证服务的可靠性。本文针对卫星传输网络高时延、有突发性误码的特点,为了让传输更高效,就TCP协议的改进做些分析。     

VoIP transmission mechanism based on TCP

As the widespread employment of firewalls on the Internet, user datagram protocol (UDP) based voice over Internet protocol (VoIP) system will be unable to transmit voice data. This paper proposed a novel method to transmit voice data based on transmission control protocol (TCP). The method adopts a disorder TCP transmission strategy, which allows discontinuous data packets in TCP queues read by application layer directly without waiting for the retransmission of lost data packets. A byte stream data boundary identification algorithm based on consistent overhead byte stuffing algorithm is designed to efficiently identify complete voice data packets from disordered TCP packets arrived so as to transmit the data to the audio processing module timely. Then, by implementing the prototype system and testing, we verified that the proposed algorithm can solve the high time delay, jitter and discontinuity problems in standard TCP protocol when transmitting voice data packets, which caused by its error control and retransmission mechanism. We proved that the method proposed in this paper is effective and practical.     

Cross-Layer design in HSDPA system to reduce the TCP effect

This paper focuses on the interaction between the transport control protocol (TCP) layer and the radio interface in the high-speed downlink packet access (HSDPA) wireless system. In the literature, studies of the interaction between TCP and wireless networks are focused on the evaluation of user bit rate in the case of dedicated channels. In this paper, the interaction between TCP, hybrid automatic repeat request (HARQ), and scheduling techniques (especially, proportional fair scheduling) is conducted. Analytical models to evaluate HSDPA cell capacity, user bit rate, and interaction with TCP layer are presented. Even if as expected the bit rate per flow decreases strongly with the congestion frequency in the wired network, it is shown that the overall capacity achieved by HSDPA is not as affected by the TCP layer. Using this result, a method to reduce the effect of TCP on wireless network without losing much cell capacity is proposed. This method has the advantage of modifying the scheduling algorithm only and of not requiring any change to the TCP protocol.     

基于多协议的人工影响天气中转服务器

为了满足人工影响天气不同作业决策时段需求,设计了一种基于混合TCP - UDP协议的人工影响天气中转服务器.连接双方(指挥端和客户端)的指令通讯协议采用混合TCPUDP算法的传输协议进行数据连接.该机制使用UDP作为短对话时的传输层协议,而对于大量数据需要传输时则使用TCP作为传输层的协议.这样,对于短对话可以避免TCP的额外开销,而对于长对话又可以得到由TCP提供的可靠传输和拥塞控制.     

一种基于卫星IP网络的数据链路层协议

通过分析卫星通信网络发展趋势,阐述卫星网络中现有的数据链路层协议,梳理归纳卫星网络的特点及影响,提出了一种新型卫星网络数据链路层协议(New Satellite Link Protocol,NSLP)。分析对比表明,该协议能够有效降低链路层报头开销,提高信息传输效率。在实际应用中,新型协议具有能够简化数据链路层的功能,有与TCP/IP协议兼容性好、与IP协议耦合度高、节约星上资源等诸多优点,有利于卫星IP网络整体性能的有效提升。     

QUIC协议研究

为了解决当前TCP传输存在的两个主要问题:(1)建立连接、断开连接的耗时传输机制;(2)前序包阻塞(Head-of-line blocking,HOL)问题,本文介绍一种基于UDP作为底层传输的全新协议(Quick UDP Internet Connections,QUIC),通过采用UDP为传输层协议,避免建立连接、断开连接的耗时问题和前序包阻塞问题,并且通过一种巧妙的机制保证可靠性传输,克服UDP传输存在的问题.     

Parallel transport: a new transport layer paradigm for enabling Internet quality of service

The transport layer in the network protocol stack serves as a liaison between the application and the underlying network. Any quality of service provided by the network thus has to be effectively translated by the transport layer protocol in order to be enjoyed by the applications. In this article, we argue for a fundamental rethinking of the transport layer design to facilitate such QoS delivery. We identify the key requirement for a QoS enabling transport layer protocol as the ability to effectively handle multiplicity in terms of user differentiation levels, network resources, and service models. However, TCP, the transport layer protocol predominantly used in the Internet, is unable to support such multiplicity due to its single-state design. We extend TCP to a parallel transport layer protocol called parallel TCP (pTCP) that can tackle the different dimensions of multiplicity, and hence enable varying classes of QoS to applications. We discuss the applicability of pTCP in three specific domains with different levels of network support for QoS, and present simulation results substantiating our arguments.     

基于卫星信道的TCP/IP传输性能研究

本文通过介绍卫星传输以及TCP/IP传输协议的各自优势,对两者相结合的TCP/IP over SatNet通信方式存在的链路时延过长以及误码率过高等问题进行了分析,并从TCP算法层和链路层分别寻求了多种解决方案,使得Internet通过卫星传输能够较好发挥优势.     

Impact of Secondary User Block on the TCP Throughput in Cognitive Radio Sensor Networks

The cognitive radio sensor network (CRSN) has emerged as a promising solution to overcome spectrum under-utilization and spectrum scarcity problems in a resource-constrained wireless sensor network. In CRSN, TCP has to cope with a new type of packet loss due to the primary users arrival, known as secondary user blocking loss (SBL), otherwise It leads to significant TCP throughput degradation. In this paper, two main contributions are provided on the modeling of SBL and throughput evaluation of transport layer protocol for CRSN. First, it is identified two main factors of SBL and the probability of them is modeled by a discrete-time Markov chain. Second, a new congestion control algorithm is proposed to distinguish between actual congestion from the wrong congestion due to the SBL by considering the dynamic nature of CRSN. The obtained results through proposed model are verified using the COGNS framework based on NS2, which is a simulation framework for cognitive radio sensor networks. The proposed algorithm is compared with some of the well-known transport protocol TFRC-CR, OHTP and TCP Reno. The results confirm that our proposed algorithm is the best among them.

     

Transmission control protocol performance enhancement for mobile broadband interactive satellite communication system: a cross‐layer approach

Mobile broadband interactive satellite communication system is of great interest in both academic and industrial communities. However, the conventional strict‐layered protocol stack architecture and the standard TCP version perform poorly over satellite link. In this paper, we propose a comprehensive cross‐layer Transmission Control Protocol (TCP) optimization architecture while considering the main factors that affect the TCP performance. In our proposed architecture, we adopt two TCP split connection performance enhancing proxies to isolate the satellite link from the terrestrial part of the broadband satellite communication system. Then, based on the proposed cross‐layer architecture, we present an analytical model for the TCP throughput by taking the modulation and coding (ModCod) mode and the allocated bandwidth into account. In addition, we put forward a TCP‐driven bandwidth sharing and ModCod mode optimization algorithm to maximize the TCP throughput in satellite link. Extensive simulation results illustrate that our proposed comprehensive cross‐layer TCP optimization approach is able to improve the TCP throughput significantly. Copyright © 2014 John Wiley & Sons, Ltd.     

Fair and efficient Transmission Control Protocol access in the IEEE 802.11 infrastructure basic service set

When the stations in an IEEE 802.11 infrastructure basic service set employ Transmission Control Protocol (TCP), this exacerbates per‐flow unfair access problem. We propose a novel analytical model to approximately calculate the maximum per‐flow TCP congestion window limit that prevents packet losses at the access point buffer and therefore provides fair TCP access both in the downlink and uplink. The proposed analysis is unique in considering the effects of varying number of uplink and downlink TCP flows, differing round trip times among TCP connections and the use of delayed TCP acknowledgment (ACK) mechanism. Motivated by the findings of this theoretical analysis and simulations, we design a link layer access control block to be employed only at the access point in order to resolve the unfair access problem. The proposed link layer access control block uses congestion control and ACK filtering approach by prioritizing the access of TCP data packets of downlink flows over TCP ACK packets of uplink flows. Via simulations, we show that the proposed algorithm can provide both short‐term and long‐term fair accesses while improving channel utilization and access delay. Copyright © 2013 John Wiley & Sons, Ltd.