Can anyone give me an example of data plane and control plane in the 'traditional' model i.e when SDN does not apply.
I understand how SDN works, but I don't really know about the traditional model.
In SDN, the data plane and control plane are divided, so how are the data plane and control planes organized in the 'traditional' model?
In a traditional network device, the Control Plane has the L3 route processor and the L2 switch processor CPUs, which “control” the packet or data flow. Some of the different packets the control plane handles are a variety of traffic, including BPDUs, routing updates, HSRP, CDP, CEF, process-switched packets, ARP, and management traffic such as SSH, SNMP, RADIUS. All of these are processed by the router or switch’s control plane. The Data Plane (or Forwarding Plane) deals with anything that goes “through” the router/switch and not “to” the router/switch. As you can imagine there are many vendors each with their own flavor of how to best control the logic of the decision making, and also how to best handle packet flow and throughput. But the common factor here is that both the control and data planes exist on the same device, as opposed to being decoupled from each other as in SDN.
Well, first off, this is what i understand so far.
Data and Control Plane. Lets talk about traditional networking. You have multiple routers linked together. Now the routing is not static i.e. there is no fixed path to reach one computer to another in the world. The path keeps on changing depending on various parameters like hop counts / congestion / etc. So how is this dynamic nature achieved? There are routing algorithms and other mechanisms at play which decide which path to choose. Now all this decision making process form the control plane. The "brain" part in router that sends/receives packets destined for INTERMEDIATE ROUTERS ONLY and not some terminal computer connected to Internet form the control plane.
As for data plane that is actually what forwards / routes the packet to the dynamic path.
So simply put, in a traditional switch/router, the propreitory software LOCAL TO EACH ROUTER / SWITCH which is deciding the routing decision and FILLING the Switch/Router forwarding table forms the Control Plane and the FORWARDING TABLES ENTRIES ITSELF would be the data plane.
Let's say you and I are in charge of public transportation for a small city.
Before we send bus drivers out, we need to have a plan.
Control Plane = Learning what we will do
Our planning stage, which includes learning which paths the buses will take, is similar to the control plane in the network. We haven't picked up people yet, nor have we dropped them off, but we do know the paths and stops due to our plan. The control plane is primarily about the learning of routes.
In a routed network, this planning and learning can be done through static routes, where we train the router about remote networks, and how to get there. We also can use dynamic routing protocols, like RIP, OSPF and EIGRP to allow the routers to train each other regarding how to reach remote networks. This is all the control plane.
Data Plane = Actualy moving the packets based on what we learned.
Now, after the routers know how to route for remote networks, along comes a customers packet and BAM! this is were the data plane begins. The data plane is the actual movement of the customers data packets over the transit path. (We learned the path to use in the control plane stage earlier).
Let's say you and I are in charge of public transportation for a small city.
Before we send bus drivers out, we need to have a plan.
Control Plane = Learning what we will do
Our planning stage, which includes learning which paths the buses will take, is similar to the control plane in the network. We haven't picked up people yet, nor have we dropped them off, but we do know the paths and stops due to our plan. The control plane is primarily about the learning of routes.
In a routed network, this planning and learning can be done through static routes, where we train the router about remote networks, and how to get there. We also can use dynamic routing protocols, like RIP, OSPF and EIGRP to allow the routers to train each other regarding how to reach remote networks. This is all the control plane.
Data Plane = Actualy moving the packets based on what we learned.
Now, after the routers know how to route for remote networks, along comes a customers packet and BAM! this is were the data plane begins. The data plane is the actual movement of the customers data packets over the transit path. (We learned the path to use in the control plane stage earlier).
