Evolution of the IP Model

This RFC attempts to document various aspects of the IP service model and how it has evolved over time.  In particular, it attempts to document the properties of the IP layer as they are seen by upper- layer protocols and applications, especially properties that were (and, at times, still are) incorrectly perceived to exist as well as properties that would cause problems if changed.  The discussion of these properties is organized around evaluating a set of claims, or misconceptions.  Finally, this document provides some guidance to protocol designers and implementers.