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).
I'm not sure I can follow such a nice example by Keith. One simple way you can think of this is that control plane traffic is traffic that is originated by, or destined to the router itself. Data plane traffic can be simply described as traffic that is not destined to or originated by the router, but traffic that is "just passing through" to get to other destinations.
That can also be described as the Userplane and another way to understand it is how a mobile telephone call works.
When you and others can see the same cell and you try to make a call that is part of the CNBAP I.E. Common Node B Application Part, that is common to all users.
When you get authorized to make your call (You have credit on your phone or a contract) you get assigned a DNBAP I.E. Dedicated Node B Application Part, dedicated meaning that setup is for one user and you have one each. What you do on that call I.E. voice or data and how long for is up to you obviously, that part is the Userplane or Dataplane as you call it.
To keep this call up working that cell you are on needs to talk to the site and that site needs to talk to master switch which is BSC on 2g or RNC on 3g. This is called the control plane and if that control plane fails for any reason your call cannot stay up because your phone would lose communication with the cell.
I'm not sure I understand what you are asking. Things are either one or the other.
Routing protocols control where traffic goes, but are not directly responsible for the movement of them. Therefore they are control plane.
A packet moving through the router (transiting) is data plane. Those are the simple things to keep in mind.
If the router has to fully process a packet (e.g. routing protocols, SSH/Telnet/Web TO the router for administration), then it's control plane.
If the router has to simple MOVE the traffic (e.g. in one interface and out another one) then it's data plane.