共查询到19条相似文献,搜索用时 109 毫秒
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TCP(传输控制协议)拥塞控制机制直接使用在卫星网中存在很多不足。针对卫星网通信时延长、网络环境变化复杂的特点,利用TCP协议中的时间戳扩展选项,设计实现了一种改进的TCP重传和拥塞控制算法,能够根据RTr(Round Trip Time,往返时间)的变化对网络情况进行预测,从而及时重传数据包并调整窗口大小,仿真实验证明改进算法能够很好地提高TCP性能。 相似文献
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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。 相似文献
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研究了TCP层中的TCP拥塞控制算法和ATM层中的ATM拥塞算法,分析了TCPoverATM情况下两种不同拥塞算法的相互合作问题. 相似文献
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对TCP拥塞控制算法作了一些改进,以适应于无线链路传输环境.基本方法是根据TCP测量的RTT值动态估计当前链路可用带宽,重新计算并设置拥塞窗口cwnd值.仿真显示,改进后的TCP应用于无线环境性能有了较大的改进. 相似文献
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文章模拟了两个建筑楼中移动无线节点之间的数据传送情况,探讨TCP拥塞窗口控制机制在移动无线网络中的应用效果。针对具体的应用,提出了移动无线网络中TCP拥塞窗口控制机制的仿真思路,并用NS3模拟器进行了具体的仿真实现。 相似文献
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随着网络技术的发展,网络拥塞日益严重,如何解决拥塞,充分、高效地利用网络资源,成为当今急需解决的问题.由于Internet上大多数业务都采用TCP协议,因此TCP的拥塞控制机制对控制网络拥塞具有特别重要的意义.本文介绍了TCP基于窗口的拥塞控制策略和目前常用端到端拥塞控制算法,并对它们的性能进行比较. 相似文献
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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 相似文献
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This paper provides an analysis of the source policy in the rate-based congestion control scheme developed by the Asynchronous Transfer Mode (ATM) Forum for available bit rate service and derives approximate analytical closed-form expressions to describe the rate increase process. These approximations are used to analyze the impact of the source algorithm on the TCP slow-start process operating over a rate-controlled ATM network. The results show that the increase in TCP congestion window ramp-up time is noticeable when the round-trip delay is small. The results are verified by simulation 相似文献
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A new ATM adaptation layer for TCP/IP over wireless ATM networks 总被引:3,自引:0,他引:3
This paper describes the design and performance of a new ATM adaptation layer protocol (AAL‐T) for improving TCP performance
over wireless ATM networks. The wireless links are characterized by higher error rates and burstier error patterns in comparison
with the fiber links for which ATM was introduced in the beginning. Since the low performance of TCP over wireless ATM networks
is mainly due to the fact that TCP always responds to all packet losses by congestion control, the key idea in the design
is to push the error control portion of TCP to the AAL layer so that TCP is only responsible for congestion control. The AAL‐T
is based on a novel and reliable ARQ mechanism to support quality‐critical TCP traffic over wireless ATM networks. The proposed
AAL protocol has been validated using the OPNET tool with the simulated wireless ATM network. The simulation results show
that the AAL‐T provides higher throughput for TCP over wireless ATM networks compared to the existing approach of TCP with
AAL 5.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Satellite ATM networks: a survey 总被引:18,自引:0,他引:18
Satellite ATM networks have significant advantages over terrestrial ATM networks. Satellites provide unique advantages such as remote coverage with rapid deployment, distance insensitivity, bandwidth on demand, immunity to terrestrial disasters, and offering broadband links. Satellite ATM networks will play an important role in the rapidly evolving information infrastructure. However, there are several obstacles which need to be overcome so that satellite ATM networks can operate in full service. The objective of this survey is to present the state of the art in satellite ATM networks and to point out open research problems. We explain the satellite ATM network architecture and cover the requirements and technical barriers for seamless integration of ATM and satellite networks. We describe the feasibility of the existing ATM cell transport methods, and deal with conventional and new satellite link access methods, and some error control schemes for the satellite environment. We then describe the problems of the proposed traffic and congestion control schemes, followed by the error performance of the Transmission Control Protocol (TCP) and Service-Specific Connection-Oriented Protocol (SSCOP) for the satellite ATM network. We present basic requirements and a possible architecture for local area-metropolitan area network (LAN-MAN) interconnection using satellite ATM and then discuss the requirements for multimedia services in satellite ATM networks 相似文献
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Traffic management for TCP/IP over satellite ATM networks 总被引:1,自引:0,他引:1
Goyal R. Jain R. Goyal M. Fahmy S. Vandalore B. Kota S. 《Communications Magazine, IEEE》1999,37(3):56-61
Several Ka-band satellite systems have been proposed that will use ATM technology to seamlessly transport Internet traffic. The ATM UBR, GFR, and ABR service categories have been designed for data. However, several studies have reported poor TCP performance over satellite ATM networks. We describe techniques to improve TCP performance over satellite ATM networks. We first discuss the various design options available for TCP end systems, IP-ATM edge devices, as well as ATM switches for long-latency connections. We discuss buffer management policies, guaranteed rate services, and the virtual source/virtual destination option in ATM. We present a comparison of ATM service categories for TCP transport over satellite links. The main goal of this article is to discuss design and performance issues for the transport of TCP over UBR, GFR, and ABR services for satellite ATM networks 相似文献
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We study the performance of bidirectional TCP/IP connections over a network that uses rate-based flow and congestion control. An example of such a network is an asynchronous transfer mode (ATM) network using the available bit rate (ABR) service. The sharing of a common buffer by TCP packets and acknowledgment (acks) has been known to result in an effect called ack compression, where acks of a connection arrive at the source bunched together, resulting in unfairness and degraded throughput. It has been the expectation that maintaining a smooth flow of data using rate-based flow control would mitigate, if not eliminate, the various forms of burstiness experienced with the TCP window flow control. However, we show that the problem of TCP ack compression appears even while operating over a rate-controlled channel. The degradation in throughput due to bidirectional traffic can be significant. For example, even in the simple case of symmetrical connections with adequate window sizes, the throughput of each connection is only 66.67% of that under one-way traffic. By analyzing the periodic bursty behavior of the source IP queue, we derive estimates for the maximum queue size and arrive at a simple predictor for the degraded throughput, for relatively general situations. We validate our analysis using simulation on an ATM network using the explicit rate option of the ABR service. The analysis predicts the behavior of the queue and the throughput degradation in simple configurations and in more general situations 相似文献
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基于TCP/IP的卫星通信传输链路的改进 总被引:2,自引:0,他引:2
卫星网络固有的一些特性影响了TCP/IP的性能。针对延迟、拥塞率、比特差错率、网络不对称性等问题,提出了支持较大的流量控制窗口及改进拥塞控制算法的方法,对现有的TCP/IP进行了改进。 相似文献
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Dynamics of TCP traffic over ATM networks 总被引:6,自引:0,他引:6
Investigates the performance of transport control protocol (TCP) connections over ATM networks without ATM-level congestion control and compares it to the performance of TCP over packet-based networks. For simulations of congested networks, the effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. The low throughput is due to wasted bandwidth as the congested link transmits cells from “corrupted” packets, i.e., packets in which at least one cell is dropped by the switch. The authors investigate two packet-discard strategies that alleviate the effects of fragmentation. Partial packet discard, in which remaining cells are discarded after one cell has been dropped from a packet, somewhat improves throughput. They introduce early packet discard, a strategy in which the switch drops whole packets prior to buffer overflow. This mechanism prevents fragmentation and restores throughput to maximal levels 相似文献