This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). It has been brought to the attention of the Journal of Parallel and Distributed Computing that an article previously published in JPDC included a large number of references to another journal. It is the opinion of the JPDC Editor-in-Chief and the Publisher that these citations were not of direct relevance to the article and were included to manipulate the citation record. This article is being retracted at the request of the Publisher, on the basis that it violates Elseviers policy regarding citation manipulation. The Editors and editorial board of JPDC were not involved in facilitating this manipulation, as the references were added after acceptance, thus avoiding editorial scrutiny.