An Enhanced Slow-Start Mechanism for TCP Vegas

2006

In this article, we present a new slow-start variant, which improves the throughput of transmission control protocol (TCP) Vegas. We call this new mechanism Gallop-Vegas because it quickly ramps up to the available bandwidth and reduces the burstiness during the slow-start phase. TCP is known to send bursts of packets during its slow-start phase due to the fast window increase and the ACK-clock based transmission. This phenomenon causes TCP Vegas to change from slow-start phase to congestionavoidance phase too early in the large bandwidth-delay product (BDP) links. Therefore, in Gallop-Vegas, we increase the congestion window size with a rate between exponential growth and linear growth during slow-start phase. Our analysis, simulation results, and measurements on the Internet show that Gallop-Vegas significantly improves the performance of a connection, especially during the slow-start phase. Furthermore, it is implementation feasible because only sending part needs to be modified.

2011

Major challenge for TCP is to keep up the new and modern generation in communications networks such as networks with large bandwidth and long delay because when TCP applies on next generation networks will suffer from degradation in performance. The reason behind this shortcoming in performance is due to the congestion control mechanisms supported by TCP variants where these mechanisms depending on linear or exponential growth to increasing the transmission window. In TCP-Vegas, in spite of the performance degrades if applied in large bandwidth-large delay networks, but it can give acceptable performance when TCP receiver support delayed acknowledgment (ACK). Vegas congestion control algorithm developed in different manner and not support the same techniques used in other TCP source variants, because it minimizes the delay in connection queue and also provides a far less in loss of packets where that increase the throughput of network. This article presents results from a series of simulation experiments designed to study TCP Vegas performance in large bandwidth and large delay network model using NS-2 network simulator. The analysis and observation of Vegas behavior performed using the main two parameters, alpha and beta, to configure the congestion window (cwnd) phases. After used multiple values, the behavior of cwnd of TCP Vegas is very sensitive to the variation of the parameters values and then we got a wide variety results corresponding to parameters variation.

Lecture Notes in Computer Science, 2005

TCP Vegas detects network congestion in the early stage and successfully prevents periodic packet loss that usually occurs in TCP Reno. It has been demonstrated that TCP Vegas achieves much higher performance than TCP Reno in many aspects. However, TCP Vegas cannot prevent unnecessary throughput degradation when congestion occurs in the backward path, it passes through multiple congested links, or it reroutes through a path with longer round-trip time (RTT). In this paper, we propose an aided congestion avoidance mechanism for TCP Vegas, called Aid-Vegas, which uses the relative one-way delay of each packet along the forward path to distinguish whether congestion occurs or not. Through the results of simulation, we demonstrate that Aid-Vegas can solve the problems of rerouting and backward congestion, enhance the fairness among the competitive connections, and improve the throughput when multiple congested links are encountered.

International Journal for Research in Applied Science and Engineering Technology, 2018

As TCP is more popular and dominant congestion control technique. TCP congestion control techniques assure reliable data transmission and detecting congestion based on packet loss or packet delay. When the network is heavily loaded there is a loss of network performance called congestion. There are two types of network that is Homogenous and Heterogeneous network and various TCP variants which can be evaluated using network simulators. There is not a fair bandwidth allocation in a homogeneous network, but fair in heterogeneous network and has a significantly lower delay. This paper will present various TCP Variants related to TCP Vegas.

Proceedings. Tenth International Conference on Parallel and Distributed Systems, 2004. ICPADS 2004., 2004

In this paper, we propose a router-based congestion avoidance mechanism (RoVegas) for TCP Vegas. TCP Vegas detects network congestion in the early stage and successfully prevents periodic packet loss that usually occurs in TCP Reno. It has been demonstrated that TCP Vegas outperforms TCP Reno in many aspects. However, TCP Vegas suffers several problems that inhere in its congestion avoidance mechanism, these include issues of rerouting, persistent congestion, fairness, and network asymmetry. By performing the proposed scheme in routers along the roundtrip path, RoVegas can solve the problems of rerouting and persistent congestion, enhance the fairness among the competitive connections, and improve the throughput when congestion occurs on the backward path. Through the results of both analysis and simulation, we demonstrate the effectiveness of RoVegas.

An important issue in designing a TCP congestion control algorithm is that it should allow the protocol to quickly adjust the end-toend communication rate to the bandwidth on the bottleneck link. However, the TCP congestion control may function poorly in high bandwidth-delay product networks because of its slow response with large congestion windows. In this paper, we propose an enhanced version of TCP Vegas called Quick Vegas, in which we present an efficient congestion window control algorithm for a TCP source. Our algorithm improves the slow-start and congestion avoidance techniques of original Vegas. Simulation results show that Quick Vegas significantly improves the performance of connections as well as remaining fair when the bandwidth-delay product increases. key words: congestion control, high bandwidth-delay product networks, TCP Vegas, transport protocol

While the demand for bandwidth increases exponentially with the growing number of internet based devices, traditional TCP algorithms are turning to be sub optimal. Delay-based congestion control algorithms which are designed to overcome this challenge, are proven to be more satisfactory than loss-based congestion algorithms. On the one hand, Loss base congestion detection technique depends solely on packet loss. On the other hand delay-based algorithms have the advantage of proactively detecting congestion occurrences based on packet delays and as a result avoiding unnecessary packet loss. TCP-Vegas as the most referred variant of delay-based algorithms is promised to achieve between 40 and 70 percent better throughput. However there is some problems which are preventing TCP-Vegas to become widespread. One of these problems is lack of fairness in bandwidth allocation while delay and loss-based connection share a link. In this paper we made some modifications on the original TCP-Vegas which enabled the new algorithm to compete fairly with loss-based algorithm.

Its more refined congestion control mechanisms, also based on the estimation of round trip delays, allow TCP Vegas to outperform the more widespread TCP Reno congestion control, based only on the packet loss detection, in a number of network environments. However, these mechanisms make TCP Vegas less aggressive with respect to TCP Reno; thereby TCP Vegas sources show high weakness in taking the available bandwidth when competing with other TCP Reno sources. This is a major reason that hinders the spread of TCP Vegas among Internet users. In this work, after a preliminary analytic study about the limits of TCP Vegas in mixed network environments, we describe a new adaptive mechanism for TCP Vegas, called TCP NewVegas, designed in order to improve its performance even in heterogeneous network scenarios. The large number of simulations, presented in this paper, show that TCP NewVegas guarantees good performance even in mixed network environments, without canceling the desirable features (e.g. fairness) that TCP Vegas exhibits in homogeneous environments.

Computer Communications, 2005

While it has been shown that TCP Vegas provides better performance compared to TCP Reno, studies have identified various issues associated with the protocol. We propose modifications to the congestion avoidance mechanism of the TCP Vegas to overcome these limitations. Unlike the solutions proposed in the past, our solution, named TCP Vegas-A, is neither dependent on optimising any critical parameter values nor on the buffer management scheme implemented at the routers and hence can be implemented solely at the end host. Our simulation experiments over wired as well as over geosynchronous and lower earth orbit satellite links show that TCP Vegas-A is able to overcome several of the identified problems-it can obtain a fairer share of the network bandwidth in wired and satellite scenarios, tackle rerouting issues, rectify Vegas's bias against higher bandwidth flows and prevail over fluctuating RTT conditions of a lower earth orbit satellite link. At the same time, Vegas-A is able to preserve the unique properties of Vegas that had made it a noteworthy protocol. q

In this paper, an Intelligent TCP Vegas (iTCP-Vegas) is proposed to im-prove the throughput of long-distance high-speed TCP connections. Large Round Tip Time (RTT) of packets in 1ong-distance networks is a problem to cause the performance degradation of original TCP connections. Although the RTT-based TCP has been recog-nized to benefit the response performance of TCP connections, the previous conservative schemes do not offers a feasible and reliably approach. For efficient response, the al-ternative approach to adapt the congestion window is proposed based on a four-stage adjustment, rather than the conventional three-stage approach. Additionally, the orig-inal TCP Vegas with constant-interval is improved by the usage of dynamic intervals. In the proposed iTCP-Vegas, the main advantages includes (1) dynamic adjustment of the parameters, α and β, to control the congestion window size values to upgrade the throughput of TCP connections on long-distance networks; (2) Simulation resul...