ich is 255. By using 255 instead of 100, we get more than twice the granularity in our measurements. Chapter 33: The Congested Network The link is saturated, but only in one direction: while rxload is 249/255, txload is only 42/255. To view this as bandwidth used, look at 4 and 5. 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. Tls, 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 33-2 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 became completely saturated in one direction. This coincides nicely with what we're seeing on the router. 1600.0 k 1200.0 k 800.0 k 400.0 k 0.0 k Figure 33-2. MRTG graph showing T1 utilization OK, SO the link is saturated. So what? We're getting our money's worth, right? If that's the case, why are users complaining of slowdowns? Let's look deeper. The first thing you should always look for is problems at the physical layer. Look for errors in the show interface output. The bold lines toward the bottom of the output do indeed indicate some errors: 819 input errors, 559 CRC, 227 frame, 0 overrun, 0 ignored, 33 abort 0 output errors, 0 collisions, 1 interface resets These two lines show input errors, CRC errors, framing errors, abort errors, and an interface reset. Hmm. Not SO good. Let's not 