Browsing by Author "Wang, Yao-Chun"

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An Extended SDN Architecture for Network Function Virtualization with a Case Study on Intrusion Prevention
(2015-05-01)
Lin, Ying-Dar
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Lin, Po-Ching
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Yeh, Chih-Hung
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Wang, Yao-Chun
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Lai, Yuan-Cheng
In conventional software-defined networking (SDN), a controller classifies the traffic redirected from a switch to determine the path to network function virtualization (NFV) modules. The redirection generates a large volume of control-plane traffic. We propose an extended SDN architecture to reduce the traffic overhead to the controller for providing NFV. The extension includes two-layer traffic classification in the data plane, extended OpenFlow protocol messages and service chaining mechanisms. Network events are analyzed in the data plane instead of the control plane. The efficiency is evaluated with a case study of intrusion prevention. The evaluation shows that only 0.12 percent of the input traffic is handled by the controller, while 77.23 percent is handled on the controller in conventional SDN.
Circuit-based logical layer 2 bridging in software-defined data center networking
(1970-01-01)
Wang, Yao-Chun
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Lin, Ying-Dar
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資訊工程學系
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Department of Computer Science
With the expansion of the size of data centers, software-defined networking (SDN) is becoming a trend for simplifying the data center network management with central and flexible flow control. To achieve L2 abstractions in a multitenant cloud, Open vSwitch (OVS) is commonly used to build overlay tunnels (eg, Virtual eXtensible Local Area Network [VXLAN]) on top of existing underlying networks. However, the poor VXLAN performance of OVS is of huge concern. Instead of solving the performance issues of OVS, in this paper, we proposed a circuit-based logical layer 2 bridging mechanism (CBL2), which builds label-switched circuits and performs data-plane multicasting in a software-defined leaf-spine fabric to achieve scalable L2 without overlay tunneling. Our evaluations indicate that direct transmission in OVS improves throughput performance by 58% compared with VXLAN tunneling, and data-plane multicasting for ARP reduces address resolution latency from 149 to 0.5 ms, compared with control-plane broadcast forwarding. The evaluation results also show that CBL2 provides 0.6, 0.4, and 11-ms protection switching time, respectively, in the presence of switch failure, link failure, and port shutdown in practical deployment.
Kinetics and Mechanisms for the Adsorption, Dissociation, and Diffusion of Hydrogen in Ni and Ni/YSZ Slabs: A DFT Study
(2012-04-03)
Weng, Meng Hsiung
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Chen, Hsin-Tsung
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Wang, Yao-Chun
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Ju, Shin-Pon
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Chang, Jee-Gong
The adsorption, dissociation, and diffusion of hydrogen in Ni(100) and Ni(100)/YSZ(100) slabs with two different interfaces (Ni/cation and Ni/O interface) have been studied by the density functional theory (DFT) with the Perdew-Wang functional. The H-2 molecule is found to preferentially absorb on a Top (T) site with side-on configuration on the Ni(100) surface, while the H-atom is strongly bound at a fcc Hollow (H) site. The barrier for the H-2 dissociation on both surfaces is calculated to be only similar to 0.1 eV. The potential energy pathways of H diffusion on pure Ni and Ni/YSZ with the two different interfaces are studied. Our calculated results show that the H-atom diffusion occurs via surface path rather than the bulk path. For the bulk path in Ni/YSZ, H-atom migration can occur more readily at the Ni/cation interface compared to the Ni/O interface. The existence of vacancy in the interface region is found to improve the mobility of H-atoms at the interface of Ni/YSZ slab. The rate constants for hydrogen dissociation and diffusion in pure Ni and Ni/YSZ are predicted.
SDN-based dynamic multipath forwarding for inter-data center networking
(2019-01-10)
Wang, Yao-Chun
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Lin, Ying-Dar
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Chang, Guey-Yun
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資訊工程學系
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Department of Computer Science
Equal-cost multipath (ECMP)-based traffic engineering (TE) methods are commonly used in intra-data center (DC) networks to improve the transmission performance for east-west traffic (ie, traffic from server to server within a DC). However, applying ECMP on inter-DC wide area network (WAN) offers limited performance enhancement as a result of irregular network topology. Since TE can be intelligently and efficiently realized with software-defined networking (SDN), SDN-based multipath becomes a popular option. However, SDN suffers from scalability issue caused by limited ternary content-addressable memory (TCAM) size. In this paper, we propose an SDN-based TE method called dynamic flow-entry-saving multipath (DFSM) for inter-DC traffic forwarding. DFSM adopts source-destination-based multipath forwarding and latency-aware traffic splitting to reduce the consumption of flow entries and achieve load balancing. The evaluation results indicate that DFSM saves 15% to 30% of system flow entries in practical topologies and reduces the standard deviation of path latencies from 10% to 7% than do label-switched tunneling, and also reduces average latency by 10% to 48% by consuming 6% to 20% more flow entries than do ECMP in less-interconnected topologies. Note that the performance gain may not always be proportional to flow entry investment, with the interconnectivity between nodes being an important factor. The evaluation also indicates that per-flow provision consumes several times the flow entries consumed by DFSM but reduces latency by 10% at most. Besides, DFSM reduces the standard deviation of path latencies from 14% to 7% than do even traffic splitting.
SDN-Based Dynamic Multipath Forwarding for Inter-Data Center Networking
(2017-01-01)
Wang, Yao-Chun
;
Lin, Ying-Dar
;
Chang, Guey-Yun
;
資訊工程學系
;
Department of Computer Science
Since traffic engineering (TE) in Software Defined Networking (SDN) can be much more efficiently and intelligently implemented, Multipath in SDN becomes a new option. However, Ternary Content Addressable Memory (TCAM) size become the bottleneck of SDN. In this paper, we propose an SDN-based Dynamic Flowentry-Saving Multipath (DFSM) mechanism for inter-DC WAN traffic forwarding. DFSM adopts source-destination-based multipath forwarding and latency-aware flow-based traffic splitting to save flow entries and achieve better load balancing. Our evaluations indicate that DFSM saves 15% to 30% system flow entries in different topologies compared to label-based tunneling, and also reduces average latency by 10% to 48% by consuming 8% to 20% more flow entries than EqualCost Multipath (ECMP) in less-interconnected topologies. In addition, compared to even traffic splitting, DFSM reduces the standard deviation of path latencies from 14% to 7%.