Kbps link. You might be tempted to say, "Hey, the link's got 33 Kbps left!" However, remember that this is a five-minute average. Perhaps an easier way to get a sense of the utilization is on line 7, which shows: reliability 255/255, txload 42/255, rxload 249/255 Looking at these numbers, you can see that the transmit load (txload) is only 42 out of 255, but the receive load (rxload) is 249 out of 255. If you use some simple math (249/255 * 100), you can see that the link is 97.65 percent utilized. Ever wonder why the rxload and txload numbers are based on 255, and not 100? The decimal number 100 in hex is 64. If we need to burn two hex digits in the router's memory, why not use them to their full- est? The largest number we can represent with two hex digits is FF, which is 255. By using 255 instead of 100, we get more than twice the granularity in our measurements. Determining Whether the Network Is Congested The link is saturated, but only in one direction: while txload is 249/255, rxload is only 42/255. To view this as bandwidth used, look at lines 16 and 17. They show we're receiving 1,509 Kbps, but transmitting only 259 Kbps. Remember that T1s are full duplex. What happens in one direction, for the most part, does not affect what happens in the other direction. T1s, like most telecom links, are full duplex. They are rated at 1.54 Mbps, and can transmit this speed in both directions simultaneously. An even easier way to see whether your links are saturated is to deploy a tool such as the Multi Router Traffic Grapher (MRTG), which gives you a quick graphical repre- sentation of the traffic on your links. Figure 31-2 shows an MRTG graph for this link. Each number along the bottom of the graph represents an hour of the day. The small triangle on the righthand edge of the graph indicates the current time (i.e., the time the graph was created-in this case, 12:12 p.m.). The vertical line at 0 on the graph indicates midnight. Starting at around 9:30 or 10:00 a.m., and continuing until the current time, the link beca