确保最小发送速率的TCP友好拥塞控制算法

提出一种确保最小发送速率的TCP友好拥塞控制算法CQTCCA(certified quality TCP-friendly congestion control algorithm)。该算法通过将网络结点和端点相结合，在端点对UDP数据流采用基于公式的发送速率调整，使之体现对TCP数据流的友好性；在结点对RED进行改造，得到提供带优先级包标记的MRED算法，保证对实时多媒体数据流的最小带宽要求。仿真实验验证了本算法有效性。     

环树型TWDM-PON动态资源调度方法研究

针对基于波长变换型远端节点(RN)的环树型时分波分复用无源光网络(TWDM PON)接入网方案,提出了最大带宽利用率算法和最小切换次数算法等两种波长与时隙联合带宽分配算法。仿真结果显示了两种算法的有效性,最大带宽利用率算法可有效提高系统带宽利用率;最小切换次数算法可有效延长系统运行寿命,在现有光开关运行次数条件下系统可保证10年以上的有效运行时间。     

实时友好的网络传输MPEG-4视频全局速率控制机制

本文提出了一种改进的TFRC算法,在传统的基于TCP吞吐量模型的TFRC速率控制方案中,利用RTP和RTCP协议,结合多媒体流的特征,精确估计带宽预测模型参数.在对有效带宽预测、时延抖动、丢包率等全面分析的基础上建立了全局速率控制模型.该模型结合速率自适应MPEG-4分级编码转换机制,体现分级优先特性,较好地保证了多媒体流实时友好及传输速率的平滑性要求,并给出了一定的实验验证.     

一种自适应的FRED缓存管理算法

如何保证业务流的公平性,特别是在存在UDP业务流的情况下,有效地保护TCP流一直是一个热点研究课题.本文提出了一种自适应的FRED缓存管理算法AFRED,通过动态的调节分组丢弃的门限,保护了TCP流,提高了系统的公平性,同时保证了带宽利用的有效性.算法的复杂度与FRED相近,但是能获得更好地性能.     

一种提高无线环境中TCP性能的改进方案

本文针对无线信道的特点提出了一种用于提高无线环境中TCP性能的改进方案－Wireless-TCP，通过尝试对TCP的拥塞控制中时间的算法进行调整并增加Probe模块以应对无线信道中的长时间中断，保证TCP连接的存在，通过爱立信通信实验室的仿真实验验证了该改进方案的有效性。     

网格计算中的TCP拥塞控制

目前IP网络所应用的TCP拥塞控制机制是基于1988年Jacobson所设计的算法(慢启动和拥塞避免），虽然TCP在许多不同类型的网络中应用得很好，但在网络计算中。现有的TCP拥塞控制算法已不能有效工作。本分析了TCP传统算法在网格计算中的缺陷，并提出在罔格计算中使用新的TCP拥塞控制算法———个新的带宽增减算法。     

递归建立HS-树计算最小碰集

在基于模型的诊断中，广泛地使用冲突集来计算最小碰集的算法诊断。现有的HS－树，HST－树，BHS－树等算法普遍存在实现的困难。文章提出用递归算法建立平衡的二叉HS－树（Recursive hitting set-树，简记为RHS－树）计算最小碰集的方法，在空间复杂性与时间复杂性上能够满足大多数诊断系统中的要求。     

区分服务中一种TCP友好的公平数据包标记算法

在DiffServ网络中,存在一些对带宽利用的不公平性。为了解决这些不公平性,该文提出了一种基于TSW的标记算法,称之为TCP友好的公平数据包标记算法,它能以一种近似按比例的方式在各个汇聚流之间公平地分配网络中的剩余带宽,同时还能在汇聚流内部对TCP流和UDP流进行公平的带宽分配。通过仿真试验对算法进行了验证,并与其它几种标记算法进行比较,结果证实本算法比其它几种算法具有更好的公平性。     

基于链路冗余的层次化园区网络最小开销设计

本文从网络层次化设计及可靠性设计为出发点,在基于星型－链路－环形的网络拓扑之上,提出了新的园区网络最小开销算法,并通过实验证明其有效性和实用性。     

高速网络环境中的TCP拥塞控制算法

现有的TCP Reno在高速网络环境下存在的带宽利用率等问题,从而引出了诸如HS—TCP,S—TCP和Fast—TCP等改进的TCP拥塞控制算法。本文简单介绍三种算法,对比分析了它们存在的问题和造成的原因,并提出了可能的研究方向和目前最新的改进算法。     

Differentiated services TCP algorithm for the Internet

A new concept of the slow-start threshold hopping coefficient in the TCP Reno algorithm is proposed. A modified TCP algorithm is devised for implementing differentiated services over the Internet. A theoretical analysis and simulations are presented to validate the effectiveness of the algorithm     

Cross-layer-based adaptive TCP algorithm for cloud computing services in 4G LTE-A relaying communication

Cloud computing provides various diverse services for users accessing big data through high data rate cellular networks, e.g., LTE-A, IEEE 802.11ac, etc. Although LTE-A supports very high data rate, multi-hop relaying, and cooperative transmission, LTE-A suffers from high interference, path loss, high mobility, etc. Additionally, the accesses of cloud computing services need the transport layer protocols (e.g., TCP, UDP, and streaming) for achieving end-to-end transmissions. Clearly, the transmission QoS is significantly degraded when the big data transmissions are done through the TCP protocol over a high interference LTE-A environment. The issue of providing high data rate and high reliability transmissions in cloud computing needs to be addressed completely. Thus, this paper proposes a cross-layer-based adaptive TCP algorithm to gather the LTE-A network states (e.g., AMC, CQI, relay link state, available bandwidth, etc.), and then feeds the state information back to the TCP sender for accurately executing the network congestion control of TCP. As a result, by using the accurate TCP congestion window (cwnd) under a high interference LTE-A, the number of timeouts and packet losses are significantly decreased. Numerical results demonstrate that the proposed approach outperforms the compared approaches in goodput and fairness, especially in high interference environment. Especially, the goodput of the proposed approach is 139.42 % higher than that of NewReno when the wireless loss increases up to 4 %. Furthermore, the throughput and the response functions are mathematically analyzed. The analysis results can justify the claims of the proposed approach.     

Transport of TCP/IP traffic over assured forwarding IP-differentiated services

The Internet is facing a twofold challenge: to increase network capacity in order to accommodate a steadily increasing number of users; to guarantee the quality of service for existing applications and for new multimedia applications requiring real-time network response. In order to meet these requirements, IETF is currently defining the differentiated service (DiffServ) architecture, which should offer a simple and scalable platform to guarantee differentiated QoS in the Internet. In the DiffServ domain, the assured forwarding service is designed to provide data applications with acceptable performance, overcoming the limits of the Internet's current best-effort service. Since data applications mostly rely on the TCP transport protocol, it is important to examine the interaction between the congestion avoidance and control mechanisms of TCP and assured forwarding. Our main purpose is to shed light on this interaction, and to show that, in the current DiffServ framework, poor performance of TCP traffic flows can result from the existing mismatch between the assured forwarding traffic conditioning procedures and the TCP congestion management. We propose a new adaptive packet marking policy to deal with congestion situations that may occur. We show that, with this policy, the provisioned rate for TCP flows can be achieved.     

Performance and buffering requirements of Internet protocols overATM ABR and UBR services

ATM networks are quickly being adopted as backbones over various parts of the Internet. This article studies the dynamics and performance of the TCP/IP protocol over the ABR and UBR services of ATM networks. Specifically the buffering requirements in the ATM switches as well as the ATM edge devices. It is shown that with a good switch algorithm, ABR pushes congestion to the edges of the ATM network while UBR leaves it inside the ATM portion. As a result, the switch ABR buffer requirement for zero-packet-loss high-throughput TCP transmission is a sublinear function of the number of TCP connections     

Performance analysis of relative service using TCP‐aware marking and dynamic WRED

The implementation of successful assured forwarding (AF) services according to the DiffServ framework remains a challenging problem today, despite the numerous proposals for assured forwarding per‐hop‐behaviour (AF PHB) mechanisms and AF‐based service implementations. The interaction of the TCP and UDP traffic under an AF‐based service and a number of relative issues such as fairness among flows, achievable bandwidth guarantees and qualitative performance have been taken into consideration in this work in order to address the existing limitations. We propose two modules, the TCP‐window aware marker (TWAM) and the dynamic WRED (WRED) mechanism for implementing the differentiated services (DiffServ) AF PHB. We provide analytical models and an experimental evaluation in order to demonstrate how they succeed in enhancing the quality, improving the performance and easing the deployment of a production level AF‐based service. Copyright © 2008 John Wiley & Sons, Ltd.     

A random early demotion and promotion marker for assured services

The differentiated services (DiffServ) model, proposed to evolve the current best-effort Internet to a quality-of-service-aware Internet, provides packet level service differentiation on a per-hop basis. The end-to-end service differentiation may be provided by extending the per-hop behavior over multiple network domains through service level agreements between domains. The edge routers of each of the domains monitor the aggregate flow of the incoming packets and demote packets when the aggregate incoming traffic exceeds the negotiated interdomain service agreement. A demoted packet may encounter other edge routers on its path that have sufficient resources to route the packet with its original marking. In this paper, we propose a random early demotion and promotion (REDP) technique that works at the aggregate traffic level and allows (1) fair demotion of packets belonging to different flows, and (2) easy and fair detection and promotion of the demoted packets. Using early and random decisions on packets REDP ensures fairness in promotion and demotion. It uses a three color marking mechanism, reserving one color fur differentiating between a demoted packet and a packet with the original out-of-profile marking. We experiment with the proposed REDP scheme using the ns2 simulator for both TCP and UDP streams. The results demonstrate the fairness of REDP scheme in demoting and promoting packets. Furthermore, we show a variety of results that demonstrates that REDP provides better assured services compared to the previously proposed RIO scheme with or without the provision of promotion     

基于QoS套接字的多媒体业务QoS保障的研究

列举了基于QoS套接字的两种多媒体业务，其中一种基于UDP协议，另一种基于TCP协议。实验结果表明，增加了QoS套接字后，两种多媒体业务的性能都得到了较大的改善，但是由于TCP和UDP本身特性的不同，两种多媒体业务性能改善的程度有所不同。最后对试验结果进行了讨论并得出了一些有意义的结论。     

Enhancing satellite broadcasting services using multiresolutionmodulations

In this paper we propose to take advantage of the energy link margin that can exist of satellite connections to enrich the DVB-S services with Web-like interactive services. The exploitation of such a margin is obtained by using multiresolution modulation techniques. The system architecture analysed is asymmetrical, composed of a satellite forward link and a narrowband terrestrial reverse link. ATM is adopted to support different QoS for different types of information delivered. The satellite propagation delay and the traffic and congestion control of ATM suggest to modify the slow start and the congestion avoidance of the TCP. Our approach is based on the combination of a fixed window flow control at the transport layer with the ATM traffic and congestion control. Our analysis shows that the system performance is satisfactory if some bounds of the TCP buffer size are respected and the spacing of the resource management cells is within a given range of values     

Modeling TCP behavior in a differentiated services network

The differentiated services architecture has been proposed for providing different levels of services and has received wide attention. A packet in a diff-serv domain is classified into a class of service according to its contract profile and treated differently by its class. While many studies have addressed issues on the diff-serv architecture (e.g., dropper, marker, classifier and shaper), there have been few attempts to analytically understand a flow's behavior in a diff-serv network. We propose simple models of TCP behavior in a diff-serv network. Our models quantitatively characterize TCP throughput as functions of the contract rate, the packet-drop rate and the round-trip time in either two-drop precedence or three-drop precedence network. We also extend our models to aggregated flows. The models are validated through a number of simulations     

Design and implementation of an RSVP-based quality of servicearchitecture for an integrated services Internet

The Internet Engineering Task Force (IETF) is currently in the process of overhauling the architecture of the Internet to meet new challenges and support new applications. One of the most important components of that venture is the enhancement of the Internet service model from a classless best effort service architecture to an integrated services architecture supporting a multitude of classes and types of services. This paper presents the design, implementation, and experiences with a protocol architecture for the integrated services Internet. It is based on the emerging standards for resource reservation in the Internet, namely, the RSVP protocol and the associated service specifications defined by the IETF. Our architecture represents a major functional enhancement to the traditional TCP/IP protocol stack. It is scalable in terms of performance and number of network sessions, and supports a wide variety of network interfaces ranging from legacy LAN interfaces, such as Token Ring and Ethernet, to high-speed ATM interfaces. The paper also describes the implementation of this architecture on the IBM AIX platform and our experiences with the system. We then present a performance analysis of the system which quantifies the overheads imposed by all components of the QoS support, such as traffic policing, traffic shaping, and buffer management