We describe FAST TCP, a new TCP congestion control algorithm for high-speed long-latency networks, from design to implementation. We highlight the approach taken by FAST TCP to address the four difficulties, at both packet and flow levels, which the current TCP implementation has at large windows. We describe the architecture and characterize the equilibrium and stability properties of FAST TCP. We present experimental results comparing our first Linux prototype with TCP Reno, HSTCP, and STCP in terms of throughput, fairness, stability, and responsiveness. FAST TCP aims to rapidly stabilize high-speed long-latency networks into steady, efficient and fair operating points, in dynamic sharing environments, and the preliminary results are promising.

With the increasB us of "Virtual Machines (VMs as vehicles thatist.O1 applications running on the se. hos: it is neces sce to devis techniques that enable multipleVMs tos hare underlying resP---P.B both fairly and e#ciently.To that end, one common approach is to deploy complexresex.0 management techniques in the hos0PO infras.B11---5P.ss55.s0P , inthis paper, we advocate the us ofs5O1:---.B1:---0:. in theVMs themsem es bas- on feedback about resPR:P us05 and availability. ConsRR0. tly, we define a "Friendly" VM (FVM) to be a virtual machine that adjus--- its demand forsr.05 res5101.B s o that they are both e#ciently and fairly allocated to competing FVMs.0[ h properties areens222 us5[ one of many provably convergent control rules s uch as AIMD.By adoptingthis dis tributed application-bas--- approach to res50P2 management, itis not necesR.B to makeasP0:.B:2--- about the underlying resderly nor about the requirements of FVMs competing for thes resR---.B::--- odemonsB::--- the elegance ands implicity of our approach, wepres[ t a prototype implementation of our FVM framework inUs50O[ de Linux (UML)---an implementation thatcons[0O ofles than 500lines of code changes to UML.Wepres5 t an analytic, control-theoretic model of FVM adaptation, which es------:.B0R5 convergence andfairnes propertiesRR2. B properties areals backed up with experimental res0[R usR0 our prototype FVM implementation. 1.

There is an increasing demand for supporting real-time audiovisual services over next-generation wired and wireless networks. Various link/network characteristics make the deployment of such demanding services more challenging than traditional data applications like e-mail and the Web. These audiovisual applications are bandwidth adaptive but have stringent delay, jitter, and packet loss requirements. Consequently, one of the major requirements for the successful and wide deployment of such services is the efficient transmission of sensitive content (audio, video, image) over a broad range of bandwidth-constrained access networks. These media will be typically compressed according to the emerging ISO/IEC MPEG-4 standard to achieve high bandwidth efficiency and content-based interactivity. MPEG-4 provides an integrated object-oriented representation and coding of natural and synthetic audiovisual content for its

A novel feedback-based rate adaptation scheme is introduced and investigated in this paper. Its main innovative characteristic is the modulation of the rate increment by the distance between a flow’s present rate and an assumed targeted maximum rate as dictated by the associated application. The previous along with the shaping of the rate decrement by the reported flow’s losses are responsible for a dynamic and self-adjusting behavior that is shown to improve convergence to fairness, the oscillatory behavior of the rate and the induced packet losses when compared with the basic Additive Increase Multiplicative Decrease (AI/MD) scheme. Numerical results illustrate the good properties and intrinsic advantages of the proposed scheme both under the considered modeling assumptions, as well as under more real networking conditions by employing the ns-2 simulator. A brief comparison of the proposed scheme with the TCP-compatible schemes TFRC, IIAD and the non-AI/MD schemes AIPD, LIMPD, is included as well. Because of the aforementioned induced behavior and assumed flow’s characteristics (min and max rates), the proposed congestion control scheme seems to be appropriate for regulating the rate of streaming applications.

In the Internet, transmission systems must deal with congestion in order to keep the stability of the network. However, the model used for congestion control determines some important properties of the traffic. The most important algorithm currently used, found in the TCP protocol, has characteristics that make it unsuitable for videoconferencing systems. The aim of this dissertation is to provide an insight into the field of congestion control for such systems. In particular, this work examines one of the most promising alternatives available, TCP-Friendly Rate Control (TFRC), to answer the question “is TFRC suitable for interactive videoconferencing applications?” This dissertation presents the results obtained with TFRC, focusing on some practical aspects and providing recommendations for the implementation of such a rate-based congestion control system. This work examines the scenarios where TFRC is an adequate solution, exposing the behavior that can be expected and suggesting future improvements. The thesis also presents the experiences of integrating TFRC in the UltraGrid videoconferencing application. It shows the difficulties found, demonstrating that this integration

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The best-effort nature of the Internet poses a significant obstacle to the deployment of many applications that require guaranteed bandwidth. In this paper, we present a novel approach that enables two edge/border routers— which we call Internet Traffic Managers (ITM)—to use an adaptive number of TCP connections to set up a tunnel of desirable bandwidth between them. The number of TCP connections that comprise this tunnel is elastic in the sense that it increases/decreases in tandem with competing cross traffic to maintain a target bandwidth. An origin ITM would then schedule incoming packets from an application requiring guaranteed bandwidth over that elastic tunnel. Unlike many proposed solutions that aim to deliver soft QoS guarantees, our elastic-tunnel approach does not require any support from core routers (as with IntServ and DiffServ); it is scalable in the sense that core routers do not have to maintain per-flow state (as with IntServ); and it is readily deployable within a single ISP or across multiple ISPs. To evaluate our approach, we develop a flow-level controltheoretic model to study the transient behavior of established elastic TCP-based tunnels. The model captures the effect of cross-traffic connections on our bandwidth allocation policies. Through extensive simulations, we confirm the effectiveness of our approach in providing soft bandwidth guarantees. 1.

Real-time multimedia applications prefer smooth and predictable throughput to TCP-like abrupt sending rate changes, and this led to the development of TCP-Friendly Rate-based Congestion Control (TFRC). However, we observed a longterm throughput imbalance between TFRC and TCP sources, especially under a low level of statistical multiplexing. We set out to reduce these differences by re-introducing a TCPlike Ack mechanism while retaining the TCP throughput equation to compute the congestion window. The outcome, TCP-Friendly Window-based Congestion Control (TFWC), is fairer than TFRC when competing with TCP, and is simpler to implement in real-world applications.

ecture [1] in which some special network elements | called Trac Managers (TMs), are strategically placed (e.g., in front of clients/servers or at exchange/peering points between administrative domains). Network trac through these TM's is then characterized, regulated and classied so that internal routers are capable of managing trac to achieve specic performance goals. 1 Size-aware Network Scheduling Our rst step toward trac management is inspired by some interesting results from previous job scheduling studies. It was shown that in a system with highly variable job length distribution, few long jobs (or \elephants") request most of the system service. In such system, providing rapid response to interactive jobs which place frequent but small demands (or \mice"), can signicantly reduce the overall system average response time without penalizing long jobs. Measurements from Internet indicate that network ows, whether dened at port-toport or at network-to-network

In network protocol research a common goal is optimal bandwidth utilization, while still being network friendly. The drawback of TCP in networks with large bandwidth-delay products due to its AIMD based congestion control mechanism is well known. The congestion control algorithm of TCP has two phases namely slow-start phase and congestion-avoidance phase. Many researchers have focused on modifying the congestion avoidance phase of the algorithm. In this work, we propose a modification to the slow-start phase of the algorithm to achieve better performance. Restricted slow-start algorithm is a simple sender side alteration to the TCP congestion window update algorithm. 1.