Is there a doc that describes the object model of networks, build in arcGIS (10 and/or 9)? I mean, somewhere from which start and end nodes of edges and a list of connected edges of nodes can be inspected.
Then expand the ESRI.ArcGIS.Geodatabase and then click on the Geodatabase Namespace Object Model Diagram. This is a multi-page PDF. Page 14 is the network dataset OMD.
The important things to note are how to handle turns, how to set up your attributes (and attribute adjustments), and how to move from edge to connected edge using INetworkForwardStarEx (using INetworkForwardStarEx.QueryAdjacencies).
There is also a C++ sample on creating a custom solver, if that is what you are looking for: