This article focuses on Nagios, which is the most popular among all open-source network
monitoring software. Nagios’ popularity can be seen from its highest volume of download from
SourceForge.net, as shown in Figures 1 and 2. In addition to the SourceForge data, the Google trend,
which presents a search volume comparison of the five open-source tools, also demonstrates the high
attention of Internet users on Nagios, as shown in Figure 3. We acknowledge that these two sources of
references may not give a complete picture since there are other ways to obtain the software besides
SourceForge, such as through package management repositories of many Linux distributions. Besides,
downloading software does not necessarily mean actual software usage. However, the data does reflect
considerable interests given to Nagios over other open-source tools.