In routing, there is a process called Spanning Tree Protocol (STP) the goal of STP is to prevent a broadcast storm from switches sending information multiple paths to get to a single endpoint. This would occur in certain network topologies topology where endpoints have multiple routes to other endpoints. Instead, STP calculates the fastest route, if there was an issue with that route or communication issue then another route would be determined. 

If endpoint A was trying to reach Point D what would be the most convenient path if traffic was already observed coming from D to A?

For this example, the illustration has 5 vertices (Endpoints A,B,C,D,E)
20 edges (AB,AC,AD,AE,BA,BC,BD,BE,CA,CB,CD,CE, DA,DB,DC,DE EA,EB,EC,ED) creating an Euler path/circuit due to each vertices having 4 degrees.

This is considered a complete graph as every pair of vertices is adjacent.

E A D C B BOARD