so in this video today we will talk about the traditional network architecture and how that compares to the software-defined architecture is software-defined networking or sdn is is become a marketing buzzword that is used differently by different vendors but essentially the concept is that in traditional network the path selection decisions are made by the network devices and these network devices are anywhere from load balancers to routers and switches but whatever happens the you know if there is a link failure or router getting overloaded everything is just dependent on their own communication between the routers and switches using protocols like ospf or pgp or others rsvp lldp but it's all only visible to the network segment alone there's no communication between the network and the application so that communication doesn't exist in a traditional network whereas when you put a device like load balancer the communication is only between the load balancer and the application and still there is no visibility to from the load balancer to the network so that's a traditional network architecture where the application has absolutely no impact to the network uh or no visibility and and vice versa there is no communication between the network to the application in terms of how do we keep the services up as maximum maximize the service uptime as possible the sdn the software defined networking the past selection is made by the applications because really what's happening here the entire visibility is given to the applications and you can still put load balancers here but when you have a pure sdn architecture you really defeat the purpose now and you don't really need to but you could still use load balancers but the controller now the applications are talking to the controller network controller and then the network controller are basically talking to the network anything going wrong with the network is communicated to the controller and controller is in touch with the applications and then programs the network accordingly based on what the application wants that is how the sdn controller communicates so you have a separation of the control plane and usually the standards protocol in that actually gives you the capability of separation of a control plane with data plane is is bgp ospf has no such capabilities so bgp controllers would give you the capability of running bgp in the network on the you know network devices that are php capable making path selections and then informing the controller of what's happening in the network so that the sdn controller can you know communicate that to the application not that the application is listening but it's basically getting uh keeping a sense uh uh and checking the pulse on the applications saying hey you know if this application is overloaded i can probably switch to this application essentially a load balancing situation or scenario but it's also not only keeping a sense and then a pulse check on the application but it's also keeping a pulse check on the on the network side and and and communicating both sides both sides you know what parts of the world so that it can program the network essentially it's not programming the application it's just keeping a communication and keeping false check on the application but it's essentially the sdn controller is programming the network based on what the application wants or is capable of doing at a given point in time that's a fundamental you know architecture change where you do not see an sdn controller in a traditional network and one of the examples of this sd software-defined network is is the sd-wan architecture but that only is applicable to you know the remote sides or the branch network where your clients are coming in and there's a controller that's keeping an eye on how the van is you know behaving that's just the van part the big part of the network is the non-van part as well but you know sometimes the large enterprises have a lot of branches two thousand five thousand ten thousand band branches and they need that intelligence i've got those videos uh where you can see how sd-wan architecture works but an sdn controller and you can you know consider the sd-wan controller as an sdn controller but a pure sd sdn controller which would typically work on your lan or the data center side and keep an eye on the application communication with the application and program your data center network according to what's what's the best what's the best path or uh what's the best decision to be programmed for the network and that's really how the stn controller architectures uh are are working i have this video as an overview uh as a next video i am actually going to put this stuff in the lab and illustrate that so that you can actually put it in your lab and then get an idea of how the sdn controller can actually work talk to the application and stay in touch with the network and then program the network accordingly to get what uh to get what the application wants so that's my next part for this sdn video but this was you hope this helps