Large Graphs with Given Degree and Diameter - Part I

The following problem arises in the study of interconnection networks: find graphs of given diameter and degree having the maximum number of vertices. In this correspondence we give some constructions of graphs proving in particular that lim△∞inf N(△, D).△-D ≥ 2-D, where N(△, D) is the maximum number of vertices of a graph with degree A and diameter D.