Software Defined Networking is recent and u[coming standard,all the traditional routers are expected tp replace with SDN enabled routers.

Software defined networking architecture is an network framework which involves in separating a network’s control functions from its data forwarding functionss, and centralizing its intelligence and abstracting its underlying architecture from its applications and services.

From above definition of software defined networking we have to understand by what is the meaning of separating control functios and data function?









A typical router has two level of abstraction, the control plane which is implmented as a part of the software which implments the routing functionalities and the construction of routing table and its maangment.

The other level of abstraction ina router is a data functionailites which forwards a data packet by looking in the destination IP fi field in the IP heade,r. and making a match with the routing table, the local copy of the routing table iside the interface that is the forwarding information base, and then forward the packet to tje outgoing interface.

Traditionally both control function and data forwarding function are implemented in the single router, when they are implmented in sigle router the complexity of control function functions becomes hifger.

Why complexities becomes higger?

Because there are multiple routers with their control planes and those control planes need to coodinate with each other to generate global routing table, or to manage the global routing table and these control need to be performed in a distributed way because of its architectural linitation at the what we have designed this traditional router architecture and with these distributed control architecture the routing protocol get problemlitic and it makes network maanger diffculities if there is policy change the nedd to update each router and implementing these changes in distributed environment takes times and due to this rime there comes inconsistencies in router and causes toruble in larger network.

Maanging a subnet with some thousands routers is difficult to manage and maanging,configuration of rhese router in a distributed architecture is also difficult and a chalenging task.

Dur to thesse above complexities we gradually move from distributed control plane architecture to centralized control plane architecture and that is the basic motivation behind the design of a software defined network concept.

In software defined networking idea is that you separate out these contol planes from the routers and make a centalized control plane and you take out the brains from the routers.So, this control planes you can say that it work like a brain of the router because it makes decision and TCAM hardware just making a forwarding processing.

So, you are taking out this brains from the individual routers and putting rhis brain in a centralized olace which is your entire route controller.

So in SDN we separate control plane and data plane, the vendor only provide the hardware that is the data plane and we decide the control plane by writing tue custom logic that is the software.So the control plane will decided by the application designer or the network manager or the network support team.Where as the data plane only comes from the vendors.

So, now the vendor they will just deliver the dumb switch just have the TCAM, just has the TCAM hardware along with the forwarding engine, the control logic is not there.We will implement our control logic ourselves.

So, the vendors will only provide the hardware and we will decide the control plane by writing custom logic.

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