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Now a days, SDN (Shin, M. K., Nam, K. H., & Kim, H. J, 2012) (Kim, H., & Feamster, N. 2013) is gaining huge attraction from both the field of industry and academics area by emerging as a new network management concept. The traditional distributed network management paradigm has been replaced by the centralized control platform. SDN put forwards many prospects and methods for new network management. One essential objective of SDN is to permit a system controller, called the control plane, to ignore and deal with the whole system by designing steering instruments for hidden switches. The switches, additionally called the information plane, are exclusively liable for information sending as indicated by their sending tables. Directing calculation and system the board, are dealt with by the controller. The principal motivation behind the software defined network is to move data starting with one plane then onto the next. SDN switches are constrained by a network operating system (NOS) framework that gathers data utilizing the API and controls their sending plane, giving a theoretical model of the organization geography to the SDN regulator facilitating the applications.
Figure 1. Architecture of SDN (Devlic, A., John, W., & Sköldström, P, 2012)
Open Network Foundation (Devlic, A., John, W., & Sköldström, P, 2012) presents an elevated level engineering for SDN which are primarily part into three fundamental useful layers including framework layer, control layer and application layer as appeared in Fig. 1. It contains three principle layers: the foundation layer which bolsters the information plane activity, the control layer, and the application layers which are:
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Infrastructure Layer (Southbound): Also referred as data plane, it comprises basically of Forwarding Elements (FEs) including physical switches, for example, virtual switches and Open vSwich. These switches are accessible by methods for an open interface to switch and forward groups (Devlic, A., John, W., & Sköldström, P, 2012).
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Control Layer: The Control Layer is otherwise called the control plane, it comprises of a lot of programming based SDN controllers giving a merged control usefulness through open APIs to manage the system sending conduct through an open interface. Three correspondence interfaces permit the controllers to connect: southbound, northbound and east/westward interfaces (Devlic, A., John, W., & Sköldström, P, 2012).
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Application Layer (Northbound): It primarily comprises of the end-client business applications that expend the SDN interchanges and system administrations. Instances of such business applications incorporate system virtualization, versatility the board, and security application, etc. (Devlic, A., John, W., & Sköldström, P, 2012).
Figure 2. SDN functional layers (Cui, L., Yu, F. R., & Yan, Q, 2016)