 Let's continue with some more projects, which are implemented as SDN software defined networking frameworks for virtualizing the network functions. So we have projects such as Open Daylight, Open Flow and more. So Open Daylight or ODL is basically an initiative from the Linux Foundation. It is supported by multiple companies, which are into the open source community. So the URL is opendaylight.org. Open Daylight supports a layered architecture with integration points for the network entities as well as for the users through APIs. So if we look at the layered architecture, on the top we have the application programming interface layer. Here we have the Open Daylight graphical user interface. Example is Deluxe. We could also have third-party applications or we could have the GUI-based emulator control such as Neutron, which is from the OpenStack community. Then we have the Open Daylight APIs based on REST and NetConf and the advanced message queuing protocol. So these are different variants. This is the application layer or the API. Then we have the controller platform services and applications, where we have basic Layer 2 functionality like Layer 2 switch, tracking the host, which MAC address is connected against which particular port. Then the switch manager and topology discovery mechanism. Then in enhanced network services we have VPN, virtual tenant network, basically Neutron manager, all these things, which are not of our concern at the moment because these things would become important when implementation is carried out. In network abstraction, in order to understand what entities are connected to the networks with what resources, some policy service has to be identified and implemented, which classifies the network resources and network elements. Then we have the service abstraction layer, which abstracts away the complexities of the underlying protocols. We have OpenFlow, NetConf, the classical simple network management protocol and so forth. Then we have the data plane entities, which are the forwarding elements like OpenFlow enabled devices, proprietary, OpenV switches and other physical devices. Now this leads us to some interesting terminologies like southbound and northbound interfaces. Southbound interfaces actually are related to various underlying diverse multi-vendor network topologies and hardware. The northbound interface is where the user interacts with the Open Daylight framework, so this is comprising mostly APIs. OpenFlow is in fact the pioneering initiative or the pioneering project for implementing the network functions in a virtualized way, so it is the enabler or we can say the pioneer in Estian solutions by the Open Network Foundation. These days most of the frameworks or architectures implement ONF to coordinate between data and control planes and this helps the controller to spell out or define the flow tables on switch or a router known as the forwarding elements. Now this OpenFlow also defines APIs which are available in many emulators like Mininet for defining the flow of traffic, I mean the kind of traffic which would be sent on to particular path and then ensuring that the flow is there too. So we can see that here we have the OpenFlow block diagram which is nothing but the abstraction between the control plane and the data plane using OpenFlow APIs and on the right hand side we have the tables. Now these tables are many, so we have the OpenFlow switch that takes the policies from the OpenFlow controller and then the OpenFlow control channel shares the updates or the new policies from the controller to be shared with the data. So the data path comprises the group table that is which entities fall in a certain group and then traffic metering, policing and regulating and shaping entities are defined in the meter table. The floor table essentially is nothing but the floor table entries or the forwarding entries in every forwarding element this eventually creates a flow pipeline. Again the resources or the material has been taken from the book by Packet Publishing started to find networking with OpenStack.