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Nguyen-Ngoc, A., Lange, S., Geissler, S., Zinner, T., Tran-Gia, P.: Estimating the Flow Rule Installation Time of SDN Switches when Facing Control Plane Delay. 19th International GI/ITG Conference on “Measurement, Modelling and Evaluation of Computing Systems”. , Erlangen (2018).
The software defined networking (SDN) paradigm has numerous benefits for network operators, including cost aspects, flexibility, and programmability. In the centralized SDN architecture, the controller can order the installation of flow rules in the switches it manages via FlowMod messages. Since the processing time of these messages has a direct impact on the reaction time of the network, it is a key performance indicator for switches and quantifying it in a reliable manner is required for ensuring state consistency between the control and the data plane. Furthermore, real world deployments not only consist of different data plane hardware, but may feature varying control plane delays. Hence, in this work, we investigate the impact of such a delay on the FlowMod processing time of OpenFlow switches. Firstly, we identify a significant heterogeneity between data plane hardware in terms of processing times as well as the underlying TCP-level behavior. Secondly, we show that despite this heterogeneity, combining switch specific information with delay measurements at the controller can be used to reliably infer FlowMod processing times. We confirm our results with measurements in a dedicated testbed that is comprised of three different hardware switches, three different SDN controllers, and several high precision measurement devices.
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Nguyen-Ngoc, A., Lange, S., Zinner, T., Seufert, M., Tran-Gia, P., Aerts, N., Hock, D.: Performance Evaluation of Selective Flow Monitoring in the ONOS Controller. 4th International Workshop on Management of SDN and NFV Systems (ManSDN/NFV). , Tokio, Japan (2017).
One of the benefits when network operators adopt the Software Defined Networking (SDN) paradigm is the ability to monitor the traffic in the network without an additional network management system. Usually, SDN controllers utilize OpenFlow statistics messages in order to regularly gather information about all flows in the network. However, using the same polling interval for all flows does not take into account the heterogeneity of real world traffic and thus results in an imbalance between monitoring accuracy and control plane overhead. In particular, frequent querying results in a high resource consumption at the controller. This work proposes a Selective Flow Monitoring (SFM) mechanism that allows administrators to classify flows according to their individual requirements in terms of monitoring frequency, e.g., less frequent polling of elephant flows and frequent polling of QoS sensitive VoIP connections. We compare the performance of the SFM mechanism with the default monitoring scheme in a testbed featuring the Open Network Operating System (ONOS) controller. In this context, the CPU utilization of the controller is used as performance indicator. After identifying relevant influence factors like the number of flows and switches in the network, we investigate the viability of the approaches in different scenarios. Finally, we provide guidelines regarding their choice.
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Gebert, S., Geissler, S., Zinner, T., Nguyen-Ngoc, A., Lange, S., Tran-Gia, P.: ZOOM: Lightweight SDN-based Elephant Detection. First International Workshop on Programmability for Cloud Networks and Applications (PROCON). , Würzburg, Germany (2016).
Software Defined Networking (SDN) offers a holistic view of the network through a centralized control plane. Consequently, routing decisions can be made based on global knowledge about the network topology as well as its current state. As long living flows are suitable candidates for rerouting, their detection is crucial for efficient flow based traffic management. This work proposes the ZOOM algorithm for elephant detection in SDN networks. To this end, ZOOM follows a very lightweight approach that only uses packet counters implemented by OpenFlow switches and thus does not require any additional hardware. By exploiting this feature of OpenFlow switches, ZOOM allows lightweight and cost-effective elephant detection.
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Nguyen-Ngoc, A., Lange, S., Gebert, S., Zinner, T., Tran-Gia, P., Jarschel, M.: Performance Evaluation Mechanisms for FlowMod Message Processing in OpenFlow Switches. IEEE Sixth International Conference on Communications and Electronics. , Ha Long City, Vietnam (2016).
Network operators can benefit in terms of flexibility, cost, and vendor-independence when adopting the Software Defined Networking (SDN) paradigm. In many scenarios, the SDN controller orders the installation of new flow table entries in the switches it manages. Since such operations are handled in the slow path of the switches, the corresponding processing times constitute an important performance indicator for switches. This work focuses on a comparison of two mechanisms for evaluating the performance of OpenFlow switches with respect to the processing time of FlowMod messages. These mechanisms are characterized by different degrees of accuracy, cost, complexity, and the capability of performing measurements at run time. The first mechanism is based on the Spirent C1 dedicated testing platform, while the other uses a software module for the OpenDaylight controller. We assess their capabilities with respect to the abovementioned characteristics and quantify their accuracy by means of wiretaps that provide a ground truth regarding the measured processing times. By using three different switches in the experiments, it is possible to distinguish between hardware specific side-effects and general phenomena.
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Cofano, G., De Cicco, L., Zinner, T., Nguyen-Ngoc, A., Tran-Gia, P., Mascolo, S.: Design and Experimental Evaluation of Network-assisted Strategies for HTTP Adaptive Video Streaming. Best Student Paper Award, ACM Multimedia Systems Conference (MMSys). , Klagenfurt, Austria (2016).
In this paper we investigate several network-assisted streaming approaches which rely on active cooperation between video streaming applications and the network. We build a Video Control Plane which enforces Video Quality Fairness among concurrent video flows generated by heterogeneous client devices. To the purpose, a max-min fairness optimization problem is solved at run-time. We compare two approaches to actuate the optimal solution in an SDN network: the first one allocating network bandwidth slices to video flows, the second one guiding video players in the video bitrate selection. Performance is assessed through several QoE-related metrics, such as Video Quality Fairness, video quality, and switching frequency. The impact of client-side adaptation algorithms is also investigated.
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Lange, S., Nguyen-Ngoc, A., Gebert, S., Zinner, T., Jarschel, M., Koepsel, A., Sune, M., Raumer, D., Gallenmüller, S., Carle, G., Tran-Gia, P.: Performance Benchmarking of a Software-Based LTE SGW. 2nd International Workshop on Management of SDN and NFV Systems. , Barcelona, Spain (2015).
Network Functions Virtualization (NFV) is a concept that aims at providing network operators with benefits in terms of cost, flexibility, and vendor independence by utilizing virtualization techniques to run network functions as software on commercial off-the-shelf (COTS) hardware. In contrast, prior solutions rely on specialized hardware for each function. Performance evaluation of such systems usually requires a dedicated testbed for each individual component. Rather than analyzing these proprietary black-box components, Virtualized Network Functions (VNFs) are pieces of software that run on COTS hardware and whose properties can be investigated in a generic testbed. However, depending on the underlying hardware, operating system, and implementation, VNFs might behave differently. Therefore, mechanisms for the performance evaluation of VNFs should be similar to benchmarking of software, where different implementations are compared by applying them to predefined test cases and scenarios. This work presents a first step towards a benchmarking framework for VNFs. Given two different implementations of a VNF that acts as LTE Serving Gateway (SGW), influence factors and key performance indicators are identified and a comparison between the two mechanisms is drawn.
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Nguyen-Ngoc, A., Lange, S., Gebert, S., Zinner, T., Tran-Gia, P., Jarschel, M.: Investigating Isolation between Virtual Networks in Case of Congestion for a Pronto 3290 Switch. Workshop on Software-Defined Networking and Network Function Virtualization for Flexible Network Management (SDNFlex 2015). , Cottbus, Germany (2015).
Resource isolation between virtual networks is one of the key features of network virtualization. It is typically realized by configuring queues with specific rate guarantees on the egress ports of the network devices. The drawback of this architectural choice, however, is that traffic from several ingress ports may result in congestion on an egress port. Hence, the question arises to which extent isolation between virtual networks is realized in state-of-the-art hardware. This work aims at investigating whether congestion within one virtual network may affect the throughput performance of another virtual network. For that, measurements in a local testbed using a Pronto 3290 switch running an OpenFlow-enabling Pica8 firmware are performed.
