by Brandon Gant

I work for a library consortium in Illinois. I had been using MRTG for some time to graph the round-trip time and packet loss of ICMP Echoes sent from Chicago to each of the 45 university and college libraries around the state that connect to our servers. This historical network information was important since we would routinely get phones calls from users stating that they couldn't connect to the servers a few minutes ago, but everything works fine now. The data would show whether or not there was packet loss or long round-trip times in the Internet between us and them during the period when they couldn't connect.

With MRTG, I could never find a way to combine Round-Trip Time (milliseconds) with Packet Loss (percentage) on the same graph, so they had to be graphed separately. Using RRDTool's infinite number value (INF), I am able to put both sets of data on a single graph.

Also, with RRDTool's fetch function, I can pull information out of the RRD files for other uses. For example, a Current Status page is provided to our Help Desk so that they can check to see if a major network outage is taking place.