Software Defined Networking Architecture, Security and Energy Efficiency: A Survey <s> 4) Energy Efficient Monitoring of Traffic Conditions: <s> In this paper we present OpenTM, a traffic matrix estimation system for OpenFlow networks. OpenTM uses built-in features provided in OpenFlow switches to directly and accurately measure the traffic matrix with a low overhead. Additionally, OpenTM uses the routing information learned from the OpenFlow controller to intelligently choose the switches from which to obtain flow statistics, thus reducing the load on switching elements. We explore several algorithms for choosing which switches to query, and demonstrate that there is a trade-off between accuracy of measurements, and the worst case maximum load on individual switches, i.e., the perfect load balancing scheme sometimes results in the worst estimate, and the best estimation can lead to worst case load distribution among switches. We show that a non-uniform distribution querying strategy that tends to query switches closer to the destination with a higher probability has a better performance compared to the uniform schemes. Our test-bed experiments show that for a stationary traffic matrix OpenTM normally converges within ten queries which is considerably faster than existing traffic matrix estimation techniques for traditional IP networks. <s> BIB001 </s> Software Defined Networking Architecture, Security and Energy Efficiency: A Survey <s> 4) Energy Efficient Monitoring of Traffic Conditions: <s> The effects of data center traffic characteristics on data center traffic engineering is not well understood. In particular, it is unclear how existing traffic engineering techniques perform under various traffic patterns, namely how do the computed routes differ from the optimal routes. Our study reveals that existing traffic engineering techniques perform 15% to 20% worse than the optimal solution. We find that these techniques suffer mainly due to their inability to utilize global knowledge about flow characteristics and make coordinated decision for scheduling flows. To this end, we have developed MicroTE, a system that adapts to traffic variations by leveraging the short term and partial predictability of the traffic matrix. We implement MicroTE within the OpenFlow framework and with minor modification to the end hosts. In our evaluations, we show that our system performs close to the optimal solution and imposes minimal overhead on the network making it appropriate for current and future data centers. <s> BIB002 </s> Software Defined Networking Architecture, Security and Energy Efficiency: A Survey <s> 4) Energy Efficient Monitoring of Traffic Conditions: <s> Most network management tasks in software-defined networks (SDN) involve two stages: measurement and control. While many efforts have been focused on network control APIs for SDN, little attention goes into measurement. The key challenge of designing a new measurement API is to strike a careful balance between generality (supporting a wide variety of measurement tasks) and efficiency (enabling high link speed and low cost). We propose a software defined traffic measurement architecture OpenSketch, which separates the measurement data plane from the control plane. In the data plane, OpenSketch provides a simple three-stage pipeline (hashing, filtering, and counting), which can be implemented with commodity switch components and support many measurement tasks. In the control plane, OpenSketch provides a measurement library that automatically configures the pipeline and allocates resources for different measurement tasks. Our evaluations of real-world packet traces, our prototype on NetFPGA, and the implementation of five measurement tasks on top of OpenSketch, demonstrate that OpenSketch is general, efficient and easily programmable. <s> BIB003 </s> Software Defined Networking Architecture, Security and Energy Efficiency: A Survey <s> 4) Energy Efficient Monitoring of Traffic Conditions: <s> Software Defined Networking promises to simplify network management tasks by separating the control plane (a central controller) from the data plane (switches). OpenFlow has emerged as the de facto standard for communication between the controller and switches. Apart from providing flow control and communication interfaces, OpenFlow provides a flow level statistics collection mechanism from the data plane. It exposes a high level interface for per flow and aggregate statistics collection. Network applications can use this high level interface to monitor network status without being concerned about the low level details. In order to keep the switch design simple, this statistics collection mechanism is implemented as a pull-based service, i.e. network applications and in turn the controller has to periodically query the switches about flow statistics. The frequency of polling the switches determines monitoring accuracy and network overhead. In this paper, we focus on this trade-off between monitoring accuracy, timeliness and network overhead. We propose PayLess - a monitoring framework for SDN. PayLess provides a flexible RESTful API for flow statistics collection at different aggregation levels. It uses an adaptive statistics collection algorithm that delivers highly accurate information in real-time without incurring significant network overhead. We utilize the Floodlight controller's API to implement the proposed monitoring framework. The effectiveness of our solution is demonstrated through emulations in Mininet. <s> BIB004
Energy saving in the network can be obtained by dynamically programming the network according to traffic conditions. In order to dynamically adjust the system based on traffic flow, it is required to have updated information about the traffic conditions in the network. This necessitates need for traffic monitoring approaches to be implemented in SDN. Though these monitoring schemes are not completely accurate, they can help the controller to have an idea about traffic flow in the network including network security attacks. An approach called Open TM has been proposed in BIB001 as a query based monitoring system that relies on the features of OpenFlow switches to measure the network traffic. The information cannot be obtained from all switches as it may impose overhead on the network and consume more energy. The switch from which the traffic statistics are to be collected are intelligently chosen from the routing information present in the controller to minimize the energy consumption and boost the overall network performance. Payless has been presented in BIB004 as a pull based traffic monitoring scheme that uses adaptive statistics collection algorithm for obtaining highly error free traffic conditions in the entire network. In this method, controller queries the switches in data plane continuously for the updates regarding the traffic flow. Payless proved to be the effective method by lowering the energy consumption in the network. The drawback of this system the querying the controller continuously for maintaining accuracy which may impose overhead on the controller. FlowSense has been proposed in  as a push based monitoring method that focuses on estimating the link utilization. The switches forward the message regarding the detection of new flows to the controller using PacketIn and FlowRemoved commands based on which the controller enforces new policies into the system. These messages could favor FlowSense monitoring scheme to estimate the resource utilization, bandwidth and energy consumption in the network. OpenSketch has been proposed in BIB003 as a push based traffic flow monitoring scheme which follows the similar concept of decoupling the planes as SDN and uses three major stages namely hashing, filtering and counting. Hashing is used for providing a brief overview on the flows that needs to be measured. The filtering stage eliminates the unnecessary data and statistics are obtained in the counting stage. The results obtained are highly accurate. MicroTE has been proposed in BIB002 as a traffic monitoring scheme in the network. It dynamically adjust itself to the traffic conditions in the network and immediately respond to the changes in the network. The updates on the recent traffic conditions received from the agent installed in the server and immediately reported to the controller. OpenSample has been proposed in  as a push based monitoring scheme that relies on sFlow packet sampling tool for obtaining the packet headers from network.