On graphs for which the connected domination number is at most the total domination number

In this note, we give a finite forbidden subgraph characterization of the connected graphs for which any non-trivial connected induced subgraph has the property that the connected domination number is at most the total domination number. This question is motivated by the fact that any connected dominating set of size at least 2 is in particular a total dominating set. It turns out that in this characterization, the total domination number can equivalently be substituted by the upper total domination number, the paired-domination number and the upper paired-domination number, respectively. Another equivalent condition is given in terms of structural domination. (C) 2012 Elsevier B.V. All rights reserved.