The Coop uses MRTG, which stands for "Multi Router Traffic Grapher." MRTG interrogates our network devices every five minutes to obtain counts of the number of octets (each octet being eight data bits) passing through them. Each MRTG report page has a header identifying the port whose traffic is being graphed, and also provides four graphs, each portraying a different time scale.
By comparing each octet-count with the count that was made five minutes earlier, MRTG calculates a data rate in bits per second. (The two octet counts, made five minutes apart, are subtracted. The difference is multiplied by 8 to arrive at a number of bits. The product is divided by 300 to yield bits per second. The measured quantity is thus the average data rate during a five-minute interval.) The data rate is plotted in the "daily" graph and contributes to the six statistics that appear below the "daily" graph.
The "daily" graph. The vertical axis of the "daily" graph is bits per second (or, for a very busy port, kilobits per second). The horizontal axis is time, expressed according to the hour of the day in military (24-hour) time. The graph thus portrays about a day and a half of recent traffic. The most recent events are at the right side of the graph, and the graphed information moves toward the left as it gets older. The green points are data "in" and the blue points are data "out." For a DSL port, "in" or "green" means data passing from the DSL subscriber to the Internet, and "out" or "blue" means data passing from the Internet to the DSL subscriber.
The six statistics below the "daily" graph give the maximum traffic during the graphed period (about a day and a half), the average traffic during the graphed period, and the actual traffic during the most recent five-minute sampling interval.
The "weekly" graph. MRTG uses the stored information for the "daily" graph to derive information for the "weekly" graph. Each six data points from the "daily" graph (each data point representing a five-minute interval) are combined to yield a single data point for the "weekly" graph, indicating what happened during a thirty-minute interval. These data points are graphed to show the most recent eight days of traffic. The most recent data are graphed at the right edge of the graph, with older data to the left.
The six statistics below the "weekly" graph give the maximum traffic during the graphed period (about eight days), the average traffic during the graphed period, and the actual traffic during the most recent thirty-minute sampling interval.
The "monthly" graph. MRTG uses the stored information for the "weekly" graph to derive information for the "monthly" graph. Each four data points from the "weekly" graph (each data point representing a thirty-minute interval) are combined to yield a single data point for the "monthly" graph, indicating what happened during a two-hour interval. These data points are graphed to show the most recent five weeks of traffic. The most recent data are graphed at the right edge of the graph, with older data to the left.
The six statistics below the "monthly" graph give the maximum traffic during the graphed period (about five weeks), the average traffic during the graphed period, and the actual traffic during the most recent thirty-minute sampling interval.
The "yearly" graph. MRTG uses the stored information for the "monthly" graph to derive information for the "yearly" graph. Each twelve data points from the "monthly" graph (each data point representing a two-hour interval) are combined to yield a single data point for the "yearly" graph, indicating what happened during a twenty-four-hour interval. These data points are graphed to show the most recent thirteen months of traffic. The most recent data are graphed at the right edge of the graph, with older data to the left.
The six statistics below the "yearly" graph give the maximum traffic during the graphed period (about thirteen months), the average traffic during the graphed period, and the actual traffic during the most recent thirty-minute sampling interval.
Comparisons. We also have some "comparison" pages that are intended to permit comparison of traffic across several ports. The graphs being compared might be "daily," "weekly," "monthly,", or "yearly." You can tell what kind of graphs they are by looking to see how the horizontal axis is labeled.