6,356 research outputs found

    Enhancing Datagram Congestion Control Protocol for Efficient Long Delay Link

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    Most of the multimedia applications use the User Datagram Protocol (UDP) as a transport layer protocol because it is suitable for the delivery of multimedia data over the Internet. However, the use of UDP could endanger the stability of the network because there is no congestion control applied. To a certain extent, the network can collapse if too many applications deliberately use this protocol. Subsequently, instead of using the UDP, the applications have choices to use the Datagram Congestion Control Protocol (DCCP), which has a built-in congestion control that can provide a better network. Nevertheless, the congestion control mechanism in the CCID-2 TCP-like can cause problems when delivering multimedia data over a long delay link. To alleviate the problems, such as longer time taken for achieving maximum throughput, and throughput fluctuation during a congestion avoidance phase, two approaches have been used, i.e. setting of an appropriate slow-start threshold value and manipulating congestion window during a congestion avoidance phase. A new congestion control mechanism presented in this thesis, namely the "TCP-like Threshold Window (TCP-like TW)" is designed based on the advantages of the two approaches. It has been developed and modeled in the Network Simulator 2 (ns-2). The TCP-like TW has proven to enhance the performance of the DCCP when delivering multimedia data over long delay link networks, as well as over short delay. For a long delay link, the TCP-like TW congestion control mechanism is able to minimize the time taken to achieve the maximum throughput. It can smooth the fluctuation of throughput after achieving the maximum throughput. Furthermore, for the short delay link, the maximum throughput will be increased while maintaining the friendliness towards other congestion-controlled protocols

    Analisis dan Implementasi Protokol Snoop Terhadap Peningkatan Performansi TCP pada Jaringan Wireless

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    ABSTRAKSI: Penerapan TCP congestion avoidance dan congestion control pada jaringan nirkabel dapat memicu adanya degradasi performansi jaringan karena penyebab packet loss disebabkan oleh bit error rate yang tinggi serta putus hubungan sesaat, bukan karena kemacetan jaringan seperti pada jaringan kabel. Dengan menambahkan protokol snoop pada base station, maka sender dapat dicegah untuk menerapkan congestion avoidance dan congestion control yang tidak perlu sehingga degradasi jaringan dapat dihindari. Pengujian kinerja protokol snoop dilakukan dengan membandingkan throughput dan end to end delay pada jaringan yang menggunakan snoop dan jaringan tanpa snoop. Berdasarkan analisis hasil pengujian dapat disimpulkan bahwa performansi TCP dengan menggunakan snoop lebih baik daripada tanpa snoop. Implementasi snoop pada TCP cubic memiliki performansi yang lebih baik daripada kombinasi snoop-reno. Kata Kunci : Kata kunci : nirkabel, TCP, snoop, cubic, reno.ABSTRACT: Implementation of TCP congestion avoidance and congestion control in wireless network can trigger the degradation of network performance due to causes of packet loss caused by bit error rate is high and a second breakup, not because of network congestion as the cable network. By adding the snoop protocol at the base station, then the sender can be prevented to implement congestion avoidance and congestion control is not necessary that the network degradation can be avoided. Snoop protocol performance testing done by comparing the throughput and end-to-end delay in networks that use the network without snoop and snoop. Based on the analysis of test results can be concluded that the TCP performance for TCP Cubic by using snoop is better than no snoop. Implementation snoop on TCP cubic has a better performance than the combination snoop-reno. Keyword: Key words : wireless, TCP, snoop, cubic, reno

    Evaluation Study for Delay and Link Utilization with the New-Additive Increase Multiplicative Decrease Congestion Avoidance and Control Algorithm

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    As the Internet becomes increasingly heterogeneous, the issue of congestion avoidance and control becomes ever more important. And the queue length, end-to-end delays and link utilization is some of the important things in term of congestion avoidance and control mechanisms. In this work we continue to study the performances of the New-AIMD (Additive Increase Multiplicative Decrease) mechanism as one of the core protocols for TCP congestion avoidance and control algorithm, we want to evaluate the effect of using the AIMD algorithm after developing it to find a new approach, as we called it the New-AIMD algorithm to measure the Queue length, delay and bottleneck link utilization, and use the NCTUns simulator to get the results after make the modification for the mechanism. And we will use the Droptail mechanism as the active queue management mechanism (AQM) in the bottleneck router. After implementation of our new approach with different number of flows, we expect the delay will less when we measure the delay dependent on the throughput for all the system, and also we expect to get end-to-end delay less. And we will measure the second type of delay a (queuing delay), as we shown in the figure 1 bellow. Also we will measure the bottleneck link utilization, and we expect to get high utilization for bottleneck link with using this mechanism, and avoid the collisions in the link

    SSthreshless Start: A Sender-Side TCP Intelligence for Long Fat Network

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    Measurement shows that 85% of TCP flows in the internet are short-lived flows that stay most of their operation in the TCP startup phase. However, many previous studies indicate that the traditional TCP Slow Start algorithm does not perform well, especially in long fat networks. Two obvious problems are known to impact the Slow Start performance, which are the blind initial setting of the Slow Start threshold and the aggressive increase of the probing rate during the startup phase regardless of the buffer sizes along the path. Current efforts focusing on tuning the Slow Start threshold and/or probing rate during the startup phase have not been considered very effective, which has prompted an investigation with a different approach. In this paper, we present a novel TCP startup method, called threshold-less slow start or SSthreshless Start, which does not need the Slow Start threshold to operate. Instead, SSthreshless Start uses the backlog status at bottleneck buffer to adaptively adjust probing rate which allows better seizing of the available bandwidth. Comparing to the traditional and other major modified startup methods, our simulation results show that SSthreshless Start achieves significant performance improvement during the startup phase. Moreover, SSthreshless Start scales well with a wide range of buffer size, propagation delay and network bandwidth. Besides, it shows excellent friendliness when operating simultaneously with the currently popular TCP NewReno connections.Comment: 25 pages, 10 figures, 7 table

    Comparative Study Of Congestion Control Techniques In High Speed Networks

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    Congestion in network occurs due to exceed in aggregate demand as compared to the accessible capacity of the resources. Network congestion will increase as network speed increases and new effective congestion control methods are needed, especially to handle bursty traffic of todays very high speed networks. Since late 90s numerous schemes i.e. [1]...[10] etc. have been proposed. This paper concentrates on comparative study of the different congestion control schemes based on some key performance metrics. An effort has been made to judge the performance of Maximum Entropy (ME) based solution for a steady state GE/GE/1/N censored queues with partial buffer sharing scheme against these key performance metrics.Comment: 10 pages IEEE format, International Journal of Computer Science and Information Security, IJCSIS November 2009, ISSN 1947 5500, http://sites.google.com/site/ijcsis
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