Network Information Base (NIB) is a term used to describe the network graph that is built by a controller. Usually the network graph is built by using OpenFlow and other methods to build unified view of network topology.
The term was oft-used in a whitepaper on the Onix OpenFlow controller by Teemu Koponen et al but may be out of use by now.
A “network graph” is type of database that is optimised for graph theory/mathematics: From Wikipedia – Graph Theory
In mathematics and computer science, graph theory is the study of graphs, which are mathematical structures used to model pairwise relations between objects. A “graph” in this context is made up of “vertices” or “nodes” and lines called edges that connect them. A graph may be undirected, meaning that there is no distinction between the two vertices associated with each edge, or its edges may be directed from one vertex to another; see graph (mathematics) for more detailed definitions and for other variations in the types of graph that are commonly considered. Graphs are one of the prime objects of study in discrete mathematics.
Graph Theory is fundamental to understanding how an SDN controller can built a model of the network and calculate various paths through the topology. Although todays routing protocols like OSPF & BGP are practical instances of graph theory, I don’t think that most network engineers realise that the underlying technology is based on maths since that isn’t taught in the common curriculum such as CCNx programs (and probably rightly so)..
A blog post for the future perhaps.