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Now showing 1 - 7 of 7

Generic Validation Criteria and Methodologies for SDN Applications
(2019-12-01)
Lin, Ying-Dar
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Lai, Yu-Kuen
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Tsou, Yung-Liang
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Lai, Yuan-Cheng
;
Liou, En-Cheng
Programmable control plane in software-defined networking (SDN), plays an essential role in the SDN architecture. The network function provided by the specialized hardware in a legacy network can be created in the form of software-based "SDN application" running on the controllers to manipulate entire network configurations. Therefore, the risk of having software bugs and errors in the SDN applications may threaten the normal operations of SDN networks. This paper presents systematic validation criteria and test cases based on the proposed novel methodologies for SDN application testing. The test framework can perform testbed build-up, generate desired packet sequences, and analyze results automatically. According to the results of a generic test suite, several issues are unveiled in the application under test (AUT). Some AUTs, which need to check all the incoming packets from Open-Flow switches, fail to meet the test criteria of burst packet-in and flow self-recycling. For most of the applications based on the Ryu controller, the evaluation results reveal that some are unable to recycle flow entries after they are unloaded. It is recommended that all flows populated by SDN applications must have timeout value specified to prevent unnecessary entries kept in the flow table.
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.
Two-tier dynamic load balancing in SDN-enabled Wi-Fi networks
(2018-11-01)
Lin, Ying-Dar
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Wang, Chih Chiang
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Lu, Yi-Jen
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Lai, Yuan-Cheng
;
Yang, Hsi-Chang
This work proposes a Software Defined Networking (SDN) solution to address Wi-Fi congestion due to an unevenly distributed load among access points (APs). The conventional methods generally let client stations learn of APs' load status and select APs distributively. However, such a client-driven approach lacks a global view to make precise load balancing decisions and may result in repeated changes in client-AP association. Although several studies proposed more efficient network-controlled methods to carry out Wi-Fi load balancing, some of them are distributed methods incurring excessive message exchange among customized APs, while the rest centralized methods are found to burden the central controller with unnecessary AP association decisions. In contrast, our solution adopts standardized OpenFlow protocol and SDN controller technology to Wi-Fi networks, organizing the SDN controller and the APs into a two-tier architecture so that the controller can evaluate the degree of load balancing among the APs and decide up to which load level the APs can accept association requests without consulting the controller. From our experiment results, our solution improves Wi-Fi's load balancing degree by 34-41%, and yields an improvement of 28-36% in Wi-Fi's re-association time over generic centralized load balancing methods with positive control.
SDN-based dynamic multipath forwarding for inter-data center networking
(2019-01-10)
Wang, Yao-Chun
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Lin, Ying-Dar
;
Chang, Guey-Yun
;
資訊工程學系
;
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%.
Performance Modeling of SDN with NFV under or aside the Controller
(2017-01-01)
Fahmin, Ahmed
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Lai, Yuan-Cheng
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Hossain, Md. Shohrab
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Lin, Ying-Dar
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Saha, Dipon
Software Defined Networking (SDN) emphasizes the separation of data and control plane while network function virtualization (NFV) decouples network function from underlying hardware. Combining SDN with NFV would have many benefits, but the problem is how to integrate them. There are two possible architectures for such integration: the controller interacts with virtualized network functions (VNFs) or the switch interacts with VNFs. In this paper, the former is referred to as NFV under the controller (NFV_C) while the latter is called NFV aside the controller (NFV_AC). To the best of our knowledge, there is no analytical model for mathematically investigating the performance of such architectures. This paper therefore aims to carry out analytical modeling of SDN with NFV under or aside the controller. We model and analyze these two SDN+NFV architectures using M/M/1 queuing model and validate our analysis with various simulations. Results show that the analytical results well match the simulation results. Also a packet delay reduction of 54.67% can be achieved for NFV_AC over NFV_C, meaning that NFV_AC is a better architecture for integrating SDN with NFV.
Performance modeling and comparison of NFV integrated with SDN: Under or aside?
(2018-07-01)
Fahmin, Ahmed
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Lai, Yuan-Cheng
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Hossain, Md Shohrab
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Lin, Ying-Dar
;
資訊工程學系
Software Defined Networking (SDN) focuses on the separation of data and control plane, while network function virtualization (NFV) decouples network functions from underlying hardware. Combining SDN with NFV would have many benefits, but the problem is how to integrate them. There are two possible architectures for such integration: the controller interacts with virtualized network functions (VNFs), or the switch interacts with VNFs. In this paper, the former is referred to as NFV under the controller (NFV_C) while the latter is called NFV aside the controller (NFV_AC). To the best of our knowledge, there is no analytical model for mathematically investigating the performance of such architectures. This paper therefore reports on the analytical modeling of SDN with NFV under or aside the controller. We model and analyze these two SDN + NFV architectures using an M/M/1 queuing model and validate our analysis with various simulations. We show that the analytical results match the simulation results very well. Furthermore, a packet delay reduction of 68.83% can be achieved for NFVAC over NFVC, meaning that NFVAC is a better architecture for integrating SDN with NFV. We also consider feedback from the VNF to the switch. For low loads there is delay increase of 35.42% for high feedback (90%) in comparison with low feedback (10%). In the case of high loads we recorded a delay increase of 66.64%.

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