A bit of intro text for this memo.

documentation/design/01-introduction.md

 # Introduction
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+Data networks consists out of a variety of different network elements, link types, end hosts, services and requirements of such services. Further data networks consists not only of a single plane, but have different (logical) networking planes that have different tasks within any data network, i.e., the control plane, data plane and the network management plane. Keeping track of the different elements, links, hosts, services, their interactions, their runtime behavior on the 3 networking planes is a non-trivial tasks that is usually subsumed under the very broad term of network operations. 
+
+There are different approaches for network operations that are not only divided by their logical distinction but also how an implementer, typically network equipment vendor, is implementing the network elements and the particular operations. 
+
+We outline two basic approaches to network operation:
+* fully intergrated network operations of all networking planes, i.e., usually called the traditional approach.
+* separation of control- and data planes, i.e., usually called the Software Defined Networking (SDN) approch, though there have been implementations of this concept earlier than SDN with other names, e.g., Forwarding and Control Separation (ForCeS)
 
 ## Motivation