# SmartX Multi-View Visibility Framework
## 1 Introduction  
Recently, software-defined networking (SDN) [1] has captivated the interest of both the industry and research community since it proposes to decouple data-plane functionality from control plane functionality. Data-plane functionality for programmable packet forwarding is built into switching fabric, while the control plane functionality of managing network devices is placed in a logically centralized software controller(s). This separation simplifies network management tasks and minimizes the associated complexities of distributed network configurations. Because of the cost-effectiveness of SDN approach, it enables developers to perform various experiments, which were too costly or difficult with legacy network devices. Industry is adapting to vendor-independent interface protocols, like OpenFlow, for managing network devices [2; 3]. Cloud computing [4] is another big emerging paradigm, which attracts the interest of service providers and consumers with its pay-per-use service model, since it removes the upfront cost of purchasing physical hardware and hides networkconnectivity complexities. That is, cloud computing delivers on-demand IT resources by dynamically scaling its provisioning power. What is more, cloud computing can offer distributed intercontinental connectivity to its developers [5]. Various research works have concentrated on establishing research testbeds to provide advanced experimental networking facilities for evaluating emerging software-defined technologies. Aligned with future internet testbed projects like GENI [6] and FIRE [7], we launched OF@TEIN Playground [8] to serve as SDN-enabled multisite clouds to facilitate miniaturized academic experiments. OF@TEIN Playground is composed of ten distributed sites, spread over nine countries (i.e., Korea, Malaysia, Thailand, Indonesia, Philippines, Pakistan, Taiwan, Vietnam, and India). At the playground, multi-tenant and multisite underlay infrastructure asserts the main challenges when dealing with heterogeneous resource monitoring, flows identification, and deployed workload performance measurements. Playground resources that are distributed at multiple geographical sites, utilize multiple planes for different connectivity purposes where associated flows monitoring is very challenging. Also, playground spreads over heterogeneous underlay networks, where exploitation is easy due to lack of integrated flow monitoring support tools for the tiny-size operator team. In order to address these challenges, we are developing a multi-layered visibility (underlay, physical, and virtual resource-layers, flow-layer, and workload-layer) solution denoted as SmartX multi-view visibility framework (MVF) [9], but flow-layer visibility with the desired level of flow-centric visibility is missing and should be added. Visibility is defined as the state of being able to see or be seen. As compared to the monitoring that solely focuses on measurements data, the term visibility referred here covers both measurements data and data for tracing. Basically, flow-layer should be extended to be called flow-centric visibility that can smoothly integrate several layers of visibilities together and provide certain level of flow information such as flow type and statistics, flow class identification, flow physical-virtual topology, etc. In this paper, we list flow-centric visibility requirements for SDN-enabled multi-site clouds and then extend SmartX MVF to process multi-layer visibility data from diverse measurement points over the OF@TEIN Playground. The proposed extension of framework attempts to deliver an integrated design for both flow-centric visibility and visualization workflow. As compared to the original SmartX MVF design that focused on defining base stages, in this paper, we mainly focus on the technical details about visibility collection from distributed SmartX boxes and multi-layer visibility integration with supporting visualizations. Flow-centric visibility adopts the following approaches.