Browsing by Author "Wang, Shie-Yuan"

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A Bandwidth-Efficient INT System for Tracking the Rules Matched by the Packets of a Flow
(2019-01-01)
Wang, Shie-Yuan
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Chen, Yo-Ru
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Li, Jun-Yi
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Hu, Hsien-Wen
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Tsai, Jia-An
Tracking the rules matched by the packets of a flow when they traverse multiple switches in a network is very important and useful. In this paper, we design and implement a bandwidth-efficient In-Band Network Telemetry (INT) system that can track the rules matched by the packets of a flow in real time or in the past. We have evaluated the real performance of our system on a testbed composed of several hardware P4 switches. Our experimental results show that the system works correctly and its traffic reduction scheme can reduce the rate of generated INT reports by a factor of 39, 394, 2,055, or even up to 12,500, depending on the type of network states monitored and the threshold used to filter out less important INT reports.
A Cooperative Approach to Fully Utilizing the Aggregate Bandwidth of All Service Channels in IEEE 802.11p/1609 Networks
(2013-01-01)
Wang, Shie-Yuan
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Chiu, Hung-Wei
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Zheng, Jie
;
Chen, Xiao
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資訊工程學系
The IEEE 802.11p/1609 standards specify a suite of communication protocols for vehicular communication networks. One control channel and six service channels are used in such a network. Ideally, the data transmission load generated by all service providers and their user stations should be spread over all of the six service channels evenly to fully utilize the aggregate bandwidth of these service channels. However, the IEEE 802.11p/1609 standards do not define a way to achieve this load-balancing goal. As a result, many service providers may choose to use the same service channel and leave some service channels totally unused. This will cause heavy congestion on some service channels while wasting the bandwidth of unused service channels. To solve this problem, in this paper we propose a cooperative approach to fully utilizing the bandwidth of the six service channels in the IEEE 802.11p/1609 networks. In our approach, every service provider collects and computes the current load of the service channel that it is using and shares the computed load information with other service providers on the control channel via its WSA control packets. With this global knowledge, each service provider can choose to use an idle or lightly-used service channel to avoid heavy congestion. We used the EstiNet network simulator and emulator to conduct simulation studies. Our simulation results show that our approach significantly improves the utilization of the aggregate bandwidth of the six service channels by as high as 600%.
A rule-based inter-session network coding scheme over IEEE 802.16(d) mesh CDS-mode networks
(2012-02-02)
Wang, Shie-Yuan
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Lin, Chih-Che
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Chang, Yu-Chi
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資訊工程學系
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Department of Computer Science
In the literature, an opportunistic inter-session network coding scheme needs to exchange extra control messages to maintain traffic flow states to operate. However, such a requirement increases the implementation complexity of a network coding scheme. In this paper, we propose a rule-based network coding scheme (RNC) that performs opportunistic intersession network coding using a stateless design. By exploiting this stateless design, the proposed coding scheme is easy to implement and deploy. In addition, in this paper based on RNC we study the hidden terminal problems between different coding structures. Such a problem may result in severe packet collisions in a network-coding-based network and thus degrade network coding performance. To alleviate this problem, based on RNC we propose a smart handshake procedure (called RNC-SHP) over the IEEE 802.16(d) mesh coordinated distributed scheduling (CDS) mode to reduce the number of hidden terminals between pairwise network coding structures. Our simulation results show that the proposed RNC schemes can greatly outperform the original routing-based scheme on end-to-end flow goodputs and packet delays. (C) 2011 Elsevier B.V. All rights reserved.
A vehicle collision warning system employing vehicle-to-infrastructure communications
(2008)
Wang, Shie-Yuan
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Cheng, Yow-Wei
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Lin, Chih-Che
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Hong, Wei-Jyun
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He, Ting-Wei
Road safety has become an important issue and gained much attention for many years. To avoid vehicle collisions on the roads, researchers have proposed various collision warning systems (CWS) using different technologies. Compared with CWS using other technologies, a radio based CWS is more capable of avoiding collisions in off sight scenarios (such as the four corners of an intersection). Most existing radio based CWSs operate using vehicle to vehicle communications. However, in such CWSs, high mobility of moving vehicles easily results in message collisions and link breakage, impairing the reliability of these CWSs. An alternative is employing vehicle to infrastructure communication to build CWSs. In this paper, we propose a radio based CWS employing vehicle to infrastructure communications. Our simulation results show that the proposed CWS can effectively reduce the number of vehicle collisions without degrading the traffic throughput of a road network.
Aggregating and disaggregating packets with various sizes of payload in P4 switches at 100 Gbps line rate
(2020-09-01)
Wang, Shie-Yuan
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Li, Jun-Yi
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Lin, Yi-Bing
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資訊工程學系
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Department of Computer Science
Aggregating multiple small packets into a large packet provides many advantages. For example, multiple small packets can share a single copy of common Ethernet/IP/UDP headers to reduce the percentage of network bandwidth spent on transmitting headers. In the past, packet aggregation and disaggregation were done by a server CPU or a switch CPU, resulting in low throughputs. In this paper, we design and implement packet aggregation and disaggregation functions in the packet processing pipelines of P4 switches. Our novel designs allow packets with various sizes of payload to be aggregated and disaggregated purely in the data plane of a P4 switch. Experimental results show that the achieved throughputs of our aggregation and disaggregation methods can reach 100 Gbps, which is the line rate of the used P4 switch.
An IEEE 802.11 Cognitive Radio MAC Protocol with Dynamic Bandwidth Allocation Capabilities
(2012)
Lau, Lee-Chin
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Lin, Chih-Che
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Wang, Shie-Yuan
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資訊工程學系
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Department of Computer Science
The Cognitive Radio (CR) technology has emerged as a hot research area recently due to its high potential in addressing the spectrum underutilization problem. In this paper, the CR is applied to unauthorized CR users (CRUs) such that these nodes can access the 802.11 spectrum opportunistically to flexibly use the detected "spectrum holes," with the ultimate goal of improving the 802.11 spectrum utilization. In [5], the authors proposed a bi-directional CR MAC protocol such that the CRUs can smartly negotiate and reserve bandwidth either uni-directionally or bi-directionally, to better support both the TCP and UDP flows. However, the protocol design is inadequate in supporting traffic demands in more complicated network cases. To address this problem, we proposed a CR MAC protocol with a dynamic bandwidth allocation capability, which can well support various types of network traffic, particularly asymmetric two-way traffic flows. We used the NCTUns network simulator to conduct the study. Our simulation results show that the proposed protocols can further utilize the "spectrum holes" in a more effective way while guaranteeing QoS support to both the surrounding CRUs and authorized 802.11 nodes.
Application-Aware SDN Routing for Big Data Networking
(2015)
Cheng, Li-Wei
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Wang, Shie-Yuan
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資訊工程學系
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Department of Computer Science
Big-Data applications need to shuffle their data over a network in a very large amount. The ability to efficiently allocate network resources to quickly finish the shuffle greatly affects the overall processing speed of Big-Data applications. The recent emergence of software-defined networking (SDN) technology makes it easier for the network to integrate with a Big-Data application. The network can allocate network resources based on an application\'s run-time requirements to accelerate the speed of Big-Data delivery. In this paper, we used Hadoop as a Big-Data application platform and designed an application-aware SDN routing scheme for Hadoop to accelerate its MapReduce data shuffling over a network. Our results show that our method can outperform the ECMP-RR scheme by up to 20% and outperform the Spanning Tree method and the Floodlight OpenFlow controller by up to 70%.
Bi-directional Cognitive Radio MAC Protocol for Supporting TCP Flows
(2011)
Lau, Lee-Chin
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Lin, Chih-Che
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Wang, Shie-Yuan
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資訊工程學系
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Department of Computer Science
The Cognitive Radio (CR) technology has emerged as a recent breakthrough radio technology to meet future wireless demands in terms of both spectrum efficiency and performance of new wireless applications. In an 802.11 Cognitive Radio Network (CRN), when the spectrum is not used, unauthorized users with CRs can access the frequencies assigned to authorized users in an opportunistic manner, thus dramatically improving spectrum efficiency of the network. In [5], the authors proposed a CR MAC protocol for 802.11 CRNs such that the unauthorized CR users (CRUs) can flexibly use the "spectrum holes" without affecting the performance of the authorized users. However, the protocol design proposed in [5] can degrade the throughput performance of TCP flows. Since TCP is a primary transport protocol for most of the internet applications today, it is imperative that a proposed CR MAC protocol can well support TCP flows. To address this problem, in this paper we propose a Bi-directional CR MAC (Bi-MAC) protocol such that the CRUs can smartly negotiate and reserve bandwidth based on the anticipated packet exchanges on the data channels. Our simulation results show that the Bi-MAC protocol can effectively improve both the TCP and UDP performance of CRUs and increase the network goodputs.
Boosting the OpenFlow Control-Plane Message Exchange Performance of OpenvSwitch
(2015)
Chiu, Hung-Wei
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Wang, Shie-Yuan
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資訊工程學系
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Department of Computer Science
The SDN (Software-defined Networking) technology is a new and important technology for next-generation networks. In the current usages of SDN, the most well-known and mature protocol between an SDN controller and SDN switches is the OpenFlow protocol. OpenvSwitch is a software switch that supports the OpenFlow protocol. An OpenvSwitch is commonly run in a physical server to connect all of the virtual machines running on the server with a real network. In addition, it can run on a stand-alone Linux system to make the Linux system and its network interface cards act as a hardware switch. This paper proposes a new design and implementation for OpenvSwitch running on Linux to boost its OpenFlow control-plane message exchange performance. Our results show that our design and implementation can improve the performance by up to 58%.
Building A Prototype of a Pair of Weighing Shoes Based on Machine Learning Techniques
(2019-01-01)
Wang, Shie-Yuan
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Jenp, En-Yu
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Hsu, Ya-Jen
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資訊工程學系
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Department of Computer Science
Changes in the human body weight may be caused by diseases, overeating, lack of exercise, or other health problems. In this paper, we built a prototype of a pair of weighing shoes to enable people to constantly monitor their weight changes so that they can detect and treat their health problems earlier. We placed several thin and flexible pressure sensors under the shoes and used machine learning techniques to learn the relationship between their values and the actual weight of the human body being measured. The trained model then was used to predict the weight of a human body. In our experiments, we varied the number of used pressure sensors to study its impact on the prediction error. We found that the prediction error of the trained model could be controlled within 5.8% when 8 or more pressure sensors were used for the current prototype.
Constructing an Optimal Spanning Tree Over a Hybrid Network with SDN and Legacy Switches
(2015)
Wang, Shie-Yuan
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Wu, Chia-Cheng
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Chou, Chih-Liang
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資訊工程學系
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Department of Computer Science
In this paper, we design and implement a scheme to build an optimal spanning tree over a hybrid network composed of SDN and legacy switches. SDN is an emerging network technology and gradually gaining adoption worldwide. However, during the technology transition period, which may last several years from now on, inevitably SDN switches and legacy switches will need to coexist in a network. In a legacy network with loops, the IEEE 802.11D distributed spanning tree protocol is used to construct a spanning tree to avoid the packet broadcast storm problem. In an SDN network, the SDN controller can use the collected global knowledge of the network topology to centrally construct a spanning tree to solve this problem. However, so far there is no scheme to integrate together the spanning trees separately built in multiple isolated legacy networks and isolated SDN networks to build an optimal spanning tree across the hybrid network. Our scheme presented in this paper is the first scheme designed and implemented for this purpose. In this paper, we used the EstiNet OpenFlow network simulator and emulator to simulate hybrid networks. Our scheme is implemented as a module of the Floodlight SDN controller to construct an optimal spanning tree over the simulated hybrid networks. Our simulation results show that our scheme can correctly generate an optimal spanning tree based on two performance metrics: the average path latency and the average path throughput of a spanning tree.
Design and Implementation of A more Realistic Radio Propagation Model for Wireless Vehicular Networks over the NCTUns Network Simulator
(2011)
Wang, Shie-Yuan
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Wang, Po-Fan
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Li, Yu-Wei
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Lau, Lee-Chin
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資訊工程學系
Today, Intelligent Transportation System (ITS) applications has made a great impact on improving the quality and efficiency of the transportation system. This achievement has attracted researchers to propose more ITS applications, particularly to improve the transportation safety through Vehicular Ad Hoc Networks (VANETs). The major difficulty faced by these researchers is the verification of their proposals or ideas through field-trials or real-world experiments. Therefore, VANET simulator becomes the best and the most economical alternative to verify the validity and reliability of a proposed ITS application. Among all the VANET simulators, the NCTUns 6.0 appears as one of the most powerful tool due to its integrated platform of network simulation and microscopic traffic simulation. To further enhance the capability of NCTUns 6.0, we design and implement a more realistic radio propagation model, specifically for VANETs simulation. Through extensive simulations, it is shown that the adoption of a more realistic channel model has greatly affected the vehicles' behavior, as compared to the commonly used two-ray ground channel model.
Design and Implementation of a Packet-in Buffer System for SDN Switches
(2017-01-01)
Wang, Shie-Yuan
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Chang, Chun-Hao
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Hsieh, Yi-Hsuan
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Chou, Chih-Liang
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資訊工程學系
In this paper, we designed, implemented, and evaluated the performance of a Packet-in packet buffer system in an SDN bare metal commodity switch and Open vSwitch. In our approach, only the first packet of a new flow needs to be sent to the SDN controller via a Packet-in packet and all subsequent packets can be temporarily stored in the Packet-in packet buffer system until the arrival of the flow rule. Our experimental results show that our approach effectively prevents packets of a new flow from being dropped when they pass an SDN switch, significantly reduces the switch CPU usage, greatly reduces the control plane bandwidth usage, and greatly reduces the Packet-in packet processing load imposed on the SDN controller.
Design and Implementation of TCP-Friendly Meters in P4 Switches
(2020-08-01)
Wang, Shie-Yuan
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Hu, Hsien-Wen
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Lin, Yi-Bing
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資訊工程學系
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Department of Computer Science
Metering the traffic of a flow and dropping the portion of traffic that exceeds the target rate set by the meter is very important to provide quality of service (QoS) in a network. Most existing switches on the market provide the meter function. Although these meters regulate the traffic of a UDP flow very well, according to our tests, they are not TCP-friendly. For example, we found that a TCP flow passing the meter of a commercial switch can only achieve about 10% of the target rate. Based on our studies, we found that this poor performance is due to the bad interactions between the TCP congestion control and the meter function. In this paper, we design and implement a TCP-friendly meter in the packet processing pipelines of a P4 switch. Experimental results show that our meter regulates a TCP flow very well and can maintain its achieved rate within 5% of the target rate. Compared with the meters in several hardware switches, our meter improves the achieved rate of a TCP flow by almost 85% of the target rate.
Design, Implementation and Performance Evaluation of Software OpenFlow Flow Counters in a Bare Metal Commodity Switch
(2016)
Wang, Shie-Yuan
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Liu, Szu-Yu
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Chou, Chih-Liang
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資訊工程學系
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Department of Computer Science
In this paper, we designed, implemented, and evaluated the performance of software OpenFlow flow counters in a bare metal commodity switch. Normally, flow counters are implemented in hardware for line-rate operations and their number needs to be very large to support a large flow-based SDN network. Although these hardware counters operate very fast, they greatly increase the cost of an OpenFlow switch. In addition, due to the limited chip size of the switching ASIC used in an OpenFlow switch, the number of hardware counters cannot scale to a large number. To overcome these drawbacks, we designed and implemented software flow counters in a 48 port x 10 Gbps (port bandwidth) bare metal commodity switch and evaluated their performance and limitations. This paper also reports important findings obtained from this practical work.
Enhanced MAC Protocol for Cognitive Radios over IEEE 802.11 Networks
(2011)
Wang, Shie-Yuan
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Huang, Yu-Ming
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Lau, Lee-Chin
;
Lin, Chih-Che
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資訊工程學系
The Cognitive Radio (CR) technology is proposed for solving the spectrum underutilization problem and has gained great attention. By allowing unauthorized users to opportunistically access frequencies authorized to specific networks (called primary networks), the CR technology can increase the bandwidth utilization of the radio spectrum in a global perspective. In [1], the authors proposed a MAC protocol for CRs that aims to "borrow" the link bandwidth from IEEE 802.11 networks. This protocol allows CR users to opportunistically exchange data on an idle 802.11 channel. However, the protocol proposed in [1] selects an 802.11 channel for data exchange in a random manner. This random channel selection process is time-consuming for CR users to start a data transmission. In addition, the protocol does not consider the effects of hidden terminals (HTs), which often exist in wireless networks and significantly decrease the goodputs of a network. To address these problems, in this paper we propose enhancements to the protocol proposed in [1]. The proposed protocol is evaluated using extensive simulations. Our simulation results show that our proposed protocol can effectively decrease the time required for finding an idle 802.11 channel to transmit data and therefore increase the network goodputs in networks with and without the existence of HTs.
EstiNet OpenFlow Network Simulator and Emulator
(2013-09-01)
Wang, Shie-Yuan
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Chou, Chih-Liang
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Yang, Chun-Ming
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資訊工程學系
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Department of Computer Science
In this article, we introduce the EstiNet OpenFlow network simulator and emulator, and present its support for testing the functions and evaluating the performances of software-defined networks' OpenFlow controller's application programs. EstiNet uses an unique kernel re-entering simulation methodology to enable unmodified real applications to run on nodes in its simulated network. As a result, without any modification, real NOX/POX or Floodlight OpenFlow controllers can readily run on a host in an EstiNet simulated network to control thousands of simulated OpenFlow switches. EstiNet has the characteristics of a simulator and an emulator at the same time. It combines the advantages of the simulation and emulation approaches without their respective shortcomings. EstiNet uses real OpenFlow controller programs, real network application programs, and the real TCP/IP protocol stack in the Linux kernel to generate correct, accurate, and repeatable SDN application performance results. In this article, we compare EstiNet with ns-3 and Mininet regarding their capabilities, performance, and scalability.
Evaluating and Improving the TCP/UDP Performances of IEEE 802.11(p)/1609 Networks
(2008)
Wang, Shie-Yuan
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Chao, Hsi-Lu
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Liu, Kuang-Che
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He, Ting-Wei
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Lin, Chih-Che
The IEEE 802.11(p)/1609 standard is an emerging technology for vehicular communication networks. It amends the IEEE 802.11-2007 standard and defines a new WAVE operational mode for vehicular environments. The WAVE mode utilizes a combined FDMA/TDMA scheme to manage network bandwidth. In this mode, a node must periodically switch its frequency channel between two different channels over time. Such a design may result in bandwidth wastage due to the residual time caused by channel switching. In this paper, we propose two easy-to-implement schemes to mitigate this problem and compare their TCP/UDP performances with those of the original scheme. Our simulation results provide many insights into the operations of these schemes on IEEE 802.11(p)/1609 networks and show that the proposed schemes always outperform the original scheme.
Evaluations of Intelligent Traffic Signal Control Algorithms under Realistic Landmark-based Traffic Patterns over the NCTUns Network Simulator
(2012)
Wang, Shie-Yuan
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Li, Yu-Wei
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資訊工程學系
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Department of Computer Science
In this paper, we use the NCTUns network simulator to study intelligent traffic signal control algorithms. NCTUns is both a microscopic traffic simulator and a network simulator. We imported the real-life map of a district of the Taipei city into NCTUns to let simulated vehicles move on the roads of the imported map. Then, we used a new and unique feature of NCTUns - each simulated vehicle moves towards its assigned landmark on the map as its destination, to create more realistic traffic patterns in the studied district. With these realistic settings, we studied an intelligent traffic signal control algorithm that has been proposed in the literature. We found that this algorithm has unfairness problems and thus we proposed two mechanisms to improve it. Our simulation results show that, when compared with the original algorithm, the improved algorithm can further reduce the average time needed for a vehicle to reach its destination. In addition, the improved algorithm can mitigate the unfairness problem.
Exploiting Event-Level Parallelism for Parallel Network Simulation on Multicore Systems
(2012-04-01)
Wang, Shie-Yuan
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Lin, Chih-Che
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Tzeng, Yan-Shiun
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Huang, Wen-Gao
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Ho, Tin-Wei
This paper proposes a parallel simulation methodology to speed up network simulations on modern multicore systems. In this paper, we present the design and implementation of this approach and the performance speedups achieved under various network conditions. This methodology provides two unique and important advantages: 1) one can readily enjoy performance speedups without using an unfamiliar simulation language/library to rewrite his protocol module code for parallel simulations, and 2) one can conduct parallel simulations in the same way as when he conducts sequential simulations. We implemented this methodology and evaluated its performance speedups on the popular ns-2 network simulator. Our results show that this methodology is feasible and can provide satisfactory performance speedups under high event load conditions on wired networks.