I. Introduction
The focus of the network alignment problem is to find approximate isomorphisms, or alignments, between similar graphs. It is widely applied to problems in bioinformatics [1], [2], database schema matching [3], ontology matching [4], and computer vision [5], [6] (where it is also known as the weighted graph matching problem). Recent algorithms solve this problem approximately for graphs with around 10,000 vertices, however there are few comparisons among them. We propose a new algorithm based on belief propagation, survey and compare existing algorithms on real and synthetic data, and investigate a problem with over 200,000 vertices.