Browsing by Author "Chou, Chih-Liang"

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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 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, 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.
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.
Hybridtrace: A Traceroute Tool for Hybrid Networks Composed of SDN and Legacy Switches
(2016)
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
Traceroute is a very useful troubleshooting tool. It reveals the routing path taken by a packet destined to a remote host. Traceroute is originally designed for the legacy IP network. However, the mechanism used by it does not work in an SDN network. In an SDN network, there has been a similar tool called SDN traceroute that provides similar functions as traceroute. However, SDN traceroute does not work in the legacy IP network. Nowadays, hybrid networks composed of both legacy and SDN switches are expected to exist for several years during the transition period. For such a hybrid network, we design and implement a tool called hybridtrace that can reveal the routing path taken by a packet that needs to traverse multiple legacy network islands and SDN network islands to reach its destination. In this paper, we present the design and implementation of hybridtrace, show the path-tracing information provided by it, and demonstrate its functions and operations.
Performance Evaluation of OpenFlow Scheduled Bundles for Consistent Updates
(2017-01-01)
Wang, Shie-Yuan
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Jhong, Chen
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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 implemented OpenFlow scheduled bundle in the Open vSwitch software switch and evaluated its performance in SDN testbed networks under different scenarios. The scheduled bundle is a very new mechanism proposed in the OpenFlow protocol for achieving consistent updates among multiple SDN switches. However, this feature has not been supported in any hardware SDN switches or any software SDN switches such as the very popular Open vSwitch software switch. As a result, no results about the performance and effectiveness of scheduled bundle have been reported in the literature. In this work, we implemented scheduled bundle in Open vSwitch, which is the first implementation of scheduled bundle in the world, and evaluated its performance and effectiveness under various scenarios.