Class InternetNode defines the canonical IP-based node in the simulator. Recall in Chapter 3 that class Node is an abstract base class that has a list of NetDevices and a list of Applications, but the protocol layers between the Applications and NetDevices are undefined in this base class. Class InternetNode provides an implementation of these IP-based layer-3 and layer-4 protocols. We envision that ports of other operating systems (such as Linux or FreeBSD) will be defined as other types of Node, hopefully with similar configuration interfaces.
This chapter provides a brief overview of the objects that make up the layer-3 and layer-4 plumbing, and by way of description, traces the path of a packet through these objects.