“MRTG is the Multi Router Traffic Grapher, a piece of free
software released under the GNU General Public License. It was
written primarily by Tobias Oetiker and Dave Rand. MRTG produces
Web pages that display graphs of bandwidth use on network links on
daily, weekly, monthly, and yearly scales. This can be an
invaluable tool for diagnosing network problems because it not only
indicates the current status of the network but also lets you
visually compare this with the history of network utilization.“MRTG relies on SNMP version one, and optionally SNMP version
two, to obtain data from routers or other network hardware. MRTG
sends SNMP requests every five minutes and stores the responses in
a specialized data format. This format allows MRTG to present the
daily, weekly, monthly, and yearly graphs without the data files
forever growing larger. It does this by summarizing the older data
as necessary. The graphs themselves are created in Portable Network
Graphics (PNG) format and can be included in Web pages or used in
other applications…”