ANALISIS PERBANDINGAN PERFORMANSI KONTROL KONGESTI TCP WESTWOOD+ DENGAN TCP NEWRENO PERFORMANCE COMPARISON ANALYSIS OF WESTWOOD+ AND NEWRENO TCP CONGESTION CONTROL

ABSTRAKSI: Mayoritas transaksi pada dunia internet terjadi di atas TCP. Hal ini disebabkan oleh kehandalan TCP dalam mentransmisi paket di dalam jaringan. Kehandalan TCP terletak pada kemampuan dalam mengontrol kongesti. Salah satu versi yang paling populer dan paling banyak digunakan hingga saat ini adalah TCP NewReno.Akan tetapi AIMD pada TCP NewReno dinilai kurang efektif dalam hal utilitas media ketika terjadi kongesti di jaringan serta ketika harus melewati loosy-medium seperti wireless. Banyak algoritma yang telah diajukan untuk meningkatkan performansi TCP NewReno, seperti TCP Westwood dan TCP Westwood+.TCP Westwood+ sendiri merupakan modifikasi dari TCP NewReno pada bagian pengirim. Ide dasar dari modifikasi ini adalah menggunakan metode endto- end bandwidth estimation serta mengganti AIMD dengan AIAD. Pada penelitian ini dilakukan pengujian terhadap efektivitas dan peningkatan performansi yang diberikan oleh Westwood+ terhadap NewReno yang berbasis simulasi.Dari hasil penelitian yang dilakukan diperoleh bahwa Westwood+ mampu meningkatkan perolehan goodput ketika terdapat ACK compression sebesar 0.118 Mbps) serta packet loss pada lossy medium (sebesar 27%). Westwood+ juga mampu meningkatkan fairness (dengan rata-rata 0.02) antar koneksi saat perbedaan RTT antar koneksi cukup signifikan. Dan juga Westwood+ memberikan goodput yang lebih tinggi (0,984 Mbps) dari NewReno 0,882 Mbps) ketika terdapat variasi route dan ukuran paket. Sedangkan unuk friendliness, Westwood+ merupakan protokol yang friendly terhadap NewReno dengan nilai korelasi di atas 0.9).Kata Kunci : TCP, Kontrol Kongesti.ABSTRACT: Almost all transaction in internet have been done over TCP. Such condition happens because of TCP’s realibility in packet transmission over the network. TCP’s realibility lies on its congestion control ability. One of the most popular version and commonly used until today is NewReno TCP.Therefore, NewReno TCP’s AIMD seems less effective in media utilization when congestion occurs also when it through lossy medium such as wireless. Many algorithms have been proposed for NewReno TCP’s perfomance enhancement, such as Westwood and Westwood+ TCP.Westwood+ TCP basicly is a modification from NewReno TCP on the sender side. The main idea is the usage of end-to-end bandwidth estimation method and relocate AIMD with AIAD. In this paper, a simulation-based research had been done to investigate effectiveness and improvement given by Westwood+ over NewReno.Result shows that Westwood+ increase goodput when ACK compression happens (0.118 Mbps improvement) and when lossy medium packet loss occurs (27% improvement). Westwood+ also enhances fairness (0.02 point of average) between connections in such condition when RTT differences between connections are significant. And Westwood+ gives higher goodput (0.984 Mbps) than NewReno (0.882 Mbps) in the presence of route and packet size variations. Also for friendliness, Westwood+ is friendly to NewReno (with coeficient point over 0.9).Keyword: TCP, Congestion Control

GTFRC, a TCP friendly QoS-aware rate control for diffserv assured service

This study addresses the end-to-end congestion control support over the DiffServ Assured Forwarding (AF) class. The resulting Assured Service (AS) provides a minimum level of throughput guarantee. In this context, this article describes a new end-to-end mechanism for continuous transfer based on TCP-Friendly Rate Control (TFRC). The proposed approach modifies TFRC to take into account the QoS negotiated. This mechanism, named gTFRC, is able to reach the minimum throughput guarantee whatever the flow’s RTT and target rate. Simulation measurements and implementation over a real QoS testbed demonstrate the efficiency of this mechanism either in over-provisioned or exactly-provisioned network. In addition, we show that the gTFRC mechanism can be used in the same DiffServ/AF class with TCP or TFRC flows

Design and analysis for TCP-friendly window-based congestion control

The current congestion control mechanisms for the Internet date back to the early 1980’s and were primarily designed to stop congestion collapse with the typical traffic of that era. In recent years the amount of traffic generated by real-time multimedia applications has substantially increased, and the existing congestion control often does not opt to those types of applications. By this reason, the Internet can be fall into a uncontrolled system such that the overall throughput oscillates too much by a single flow which in turn can lead a poor application performance. Apart from the network level concerns, those types of applications greatly care of end-to-end delay and smoother throughput in which the conventional congestion control schemes do not suit. In this research, we will investigate improving the state of congestion control for real-time and interactive multimedia applications. The focus of this work is to provide fairness among applications using different types of congestion control mechanisms to get a better link utilization, and to achieve smoother and predictable throughput with suitable end-to-end packet delay

gTFRC: a QoS-aware congestion control algorithm

This study addresses the end-to-end congestion control support over the DiffServ Assured Forwarding (AF) class. The resulting Assured Service (AS) provides a minimum level of throughput guarantee. In this context, this paper describes a new end-to-end mechanism for continuous transfer based on TCP-Friendly Rate Control (TFRC) originally proposed in [11]. The proposed approach modifies TFRC to take into account the QoS negotiated. This mechanism, named gTFRC, is able to reach the minimum throughput guarantee whatever the flow's RTT and target rate. Simulation measurements show the efficiency of this mechanism either in over-provisioned or exactly-provisioned network. In addition, we show that the gTFRC mechanism can be used in the same DiffServ/AF class with TCP or TFRC flows

Unicast UDP Usage Guidelines for Application Designers

Publisher PD

A duality model of TCP and queue management algorithms

We propose a duality model of end-to-end congestion control and apply it to understanding the equilibrium properties of TCP and active queue management schemes. The basic idea is to regard source rates as primal variables and congestion measures as dual variables, and congestion control as a distributed primal-dual algorithm over the Internet to maximize aggregate utility subject to capacity constraints. The primal iteration is carried out by TCP algorithms such as Reno or Vegas, and the dual iteration is carried out by queue management algorithms such as DropTail, RED or REM. We present these algorithms and their generalizations, derive their utility functions, and study their interaction

Application-Level QoS: Improving video conferencing quality through sending the best packet next

In a traditional network stack, data from an application is transmitted in the order that it is received. An algorithm is proposed where information about the priority of packets and expiry times is used by the transport layer to reorder or discard packets at the time of transmission to optimise the use of available bandwidth. This can be used for video conferencing to prioritise important data. This scheme is implemented and compared to unmodified datagram congestion control protocol (DCCP). This algorithm is implemented as an interface to DCCP and tested using traffic modelled on video conferencing software. The results show improvement can be made to video conferencing during periods of congestion - substantially more audio packets arrive on time with the algorithm, which leads to higher quality video conferencing. In many cases video packet arrival rate also increases and adopting the algorithm gives improvements to video conferencing that are better than using unmodified queuing for DCCP. The algorithm proposed is implemented on the server only, so benefits can be obtained on the client without changes being required to the client

System Support for Bandwidth Management and Content Adaptation in Internet Applications

This paper describes the implementation and evaluation of an operating system module, the Congestion Manager (CM), which provides integrated network flow management and exports a convenient programming interface that allows applications to be notified of, and adapt to, changing network conditions. We describe the API by which applications interface with the CM, and the architectural considerations that factored into the design. To evaluate the architecture and API, we describe our implementations of TCP; a streaming layered audio/video application; and an interactive audio application using the CM, and show that they achieve adaptive behavior without incurring much end-system overhead. All flows including TCP benefit from the sharing of congestion information, and applications are able to incorporate new functionality such as congestion control and adaptive behavior.Comment: 14 pages, appeared in OSDI 200