Jahwan Koo

NJ+: An Efficient Congestion Control Mechanism for Wireless Networks

Transmission control protocols have to overcome common problems in wireless networks. TCP employing both packet loss discrimination mechanism and available bandwidth estimation algorithm, known as the good existing solution, shows significant performance enhancement in wireless networks. For instance, TCP New Jersey which exhibits high throughput in wireless networks intends to improve TCP performance by using available bandwidth estimation and congestion warning. Even though it achieves 17% and 85% improvements in terms of goodput over TCP Westwood and TCP Reno, respectively, we further improve it by exploring maximized available bandwidth estimation, handling bit-error-rate error recovery, and effective adjustment of sending rate for retransmission timeout. Hence, we propose TCP NJ+, showing that for up to 5% packet loss rate, it outperforms other TCP variants by 19% to 104% in terms of goodput when the network is in bi-directional background traffic.

Performance Analysis of Active Queue Management Schemes for IP Network

Active Queue Management schemes have evolved over time and continue to do so. In this paper, we present a comprehensive survey of AQM schemes for IP network. Its purpose is to identify the basic approaches that have been proposed and classify them according to the design goals and performance issues of AQM schemes. The results from several performance evaluation such as the link utilization, the average delay, and the loss rates have been provided. In particular, simulation-based comparisons of AQM schemes help to understand how they differ from in terms of fairness, global synchronization, performance guarantee, complexity and scalability.

An enhanced RED-Based scheme for differentiated loss guarantees

Recently, researchers have explored to provide a queue management scheme with differentiated loss guarantees for the future Internet. The Bounded Random Drop (BRD), known as the best existing scheme, is one of such efforts which guarantees strong loss differentiation to the level of traffic in the different service classes. Even though BRD has several benefits such as low complexities and good functionalities, we identify that it has some shortcomings such as low throughput, long queuing delays, and selection problem of optimal values of parameters. Specifically, the shortcomings stem from calculating drop probabilities based on the arrival rate estimation and dropping incoming packets randomly with calculated drop probabilities without considering the current buffer occupancy. A multiple queue management scheme based on differential drop probability, called MQDDP, is proposed to overcome BRDs shortcomings as well as support absolute loss differentiation. This scheme extends the original Random Early Detection (RED), recommended by IETF for next generation Internet gateways, into multiple class-based queues by deriving the drop probability equations based on a queueing model. We also compare MQDDP to BRD for high traffic intensity and show that MQDDP has the better performance in terms of packet drop rate.

Proactive Fault Detection Schema for Enterprise Information System Using Statistical Process Control

This paper proposes a proactive fault detection schema using adaptive statistical approaches in order to enhance system availability and reliability in the heterogeneous & complicated information system environment. The proposed system applies Six Sigma SPC (Statistical Process Control) techniques already validated in industries in order to monitor the application system in the information system. This makes it possible to reduce false alarm rates for system faults and accurately detect faults by creating a control chart based on past performance data and controlling the distribution of performance based on the chart. The early detection of faults is also enabled through a fault prediction model. Therefore, the aforementioned system not only detect unknown or unseen faults but also resolve potential problems for system administrator by detecting abnormal behaviors before faults occur. In the experiment we show the superiority of our proposed model and the possibility to early detect system faults.

Analysis of RED with multiple class-based queues for supporting proportional differentiated services

The proportional differentiated service (PDS) model has been developed to provide a controllable, consistent, and scalable quality of service (QoS) model. The PDS model enables network operators to get a control knob for the convenient management of services and resources even in a large-scale network. In this paper, we provide an analysis of RED with multiple class-based queues for supporting PDS among different classes using M/M/1/K queueing model and is also verified how to set the main control parameter, maxp, of RED for PDS using ns-2 simulator.

Freeze TCPv2: An Enhancement of Freeze TCP for Efficient Handoff in Heterogeneous Networks

The advancement of mobile communications for the last few years has accompanied an increasingly extensive and diverse array of environments for TCP applications, which has led to a host of wireless TCP approaches that may provide more stability and ensure higher performance. In a heterogeneous network, as opposed to conventional wireless networks, a mobile node performs a handoff to another network cells with a different bandwidth and latency. Conventional wireless TCP schemes, however, are not capable of properly addressing sudden changes in round trip time (RTT) and packet loss resulting from handoffs within a heterogeneous network and do experience such problems as the waste of available bandwidth and frequent packet loss. As a solution to these problems, this paper proposes Freeze TCP version 2 (v2), an enhancement of Freeze TCP designed to dynamically obtain the available bandwidth in a new network cell. Comprehensive simulation study is conducted by using a network simulator, ns-2, to compare the proposed scheme to a few other schemes, such as Freeze TCP, DEMO-Vegas, and TCP Vegas, in a heterogeneous network environment with vertical handoffs in terms of throughput per speed of the mobile node and per bit error rate of the wireless link.

TCP NJ+: packet loss differentiated transmission mechanism robust to high BER environments

Transmission mechanisms that include an available bandwidth estimation algorithm and a packet loss differentiation scheme, in general, exhibit higher TCP performance in wireless networks. TCP New Jersey, known as the best existing scheme in terms of goodput, improves wireless TCP performance using the available bandwidth estimation at the sender and the congestion warning at intermediate routers. Although TCP New Jersey achieves 17% and 85% improvements in goodput over TCP Westwood and TCP Reno, respectively, we further improve TCP New Jersey by exploring improved available bandwidth estimation, retransmission timeout, and recovery mechanisms. Hence, we propose TCP New Jersey PLUS (shortly TCP NJ+), showing that under 5% packet loss rate, a characteristic of high bit-error-rate wireless network, it out-performs other TCP variants by 19% to 104% in terms of goodput even when the network is in bi-directional congestion.

TCP westwoodVT: a novel technique for discriminating the cause of packet loss in wireless networks

Conventional TCP in wireless environment cannot differentiate packet losses caused by network congestion from those caused by wireless link errors, thus, resulting in severe performance degradation. Accordingly, efficient operation of TCP in wireless networks is a critical issue in the context of differentiation between packet loss. Towards this issue, we proposes a novel technique, WestwoodVT (WestwoodNR based on TCP Vegas buffer Thresholds), which is a sender-based TCP congestion control mechanism for discriminating the cause of packet loss to enhance the performance of TCP in wireless environment. Simulation results show that, under various wireless link error rates, it achieves a maximum of 41% and 118% improvements in goodput overWestwoodNR and TCP Reno, respectively. WestwoodVT only requires changes at the send-side. Thus, it eliminates any changes to the intermediate routers unlike TCP New Jersey. Therefore, it is cost effective to implement in already deployed networks. Moreover, its fairness and friendliness are also satisfied.

Sender-Based TCP Scheme for Improving Performance in Wireless Environment

Conventional TCP in wireless environment has a lack of ability to differentiate the packet losses caused by network congestion from those caused by wireless link error. When the packet losses are due to wireless link error, TCP performance degradation occurs because of its congestion control mechanism. This paper propose a sender-side TCP scheme for discriminating the cause of packet losses. Simulation results show that it outperforms existing TCP congestion mechanisms such as WestwoodNR, TCP New Jersey, and TCP Reno in terms of goodput performance in wireless links.

On achieving proportional loss differentiation using dynamic-MQDDP with differential drop probability

More Recently, researchers have explored to provide a queue management scheme with differentiated loss guarantees for the future Internet. Various types of real time and non-real time traffic with varying requirements are transmitted over the Internet. The sides of a packet drop rate, an each class to differential drop probability on achieving a low delay and high traffic intensity. Improved a queue management scheme to be enhanced to offer a drop probability is desired necessarily. This paper considers multiple random early detection with differential drop probability which is a slightly modified version of the MQDDP model, to get the performance of the best suited, we analyzes its main control parameters (maxth, minth, maxp) for achieving the proportional loss differentiation (PLD) model, and gives their setting guidance from the analytic approach. we propose Dynamic-multiple queue management scheme based on differential drop probability, called Dynamic-MQDDP, is proposed to overcome MQDDPs shortcoming as well as supports static maxp parameter setting values for relative and each class proportional loss differentiation. MQDDP is static according to the situation of the network traffic, Network environment is very dynamic situation. Therefore maxp parameter values needs to modify too to the constantly and dynamic. The verification of the guidance is shown with figuring out loss probability using a proposed algorithm under dynamic offered load and is also selection problem of optimal values of parameters for high traffic intensity and show that Dynamic-MQDDP has the better performance in terms of packet drop rate. We also demonstrated using an ns-2 network simulation.