KRONE: 800-775-KRONE www.kroneamericas.com No part of this document may be reproduced without permission. ©2001 KRONE ® Incorporated that the answer to network perform- ance problems lies in top-down solu- tions: management software, more equipment, faster transmission speeds. KRONE ® Incorporated suggests that you first look at the foundation of your network — the structured cabling system — and work your way up. In fact, research conducted in KRONE’s laboratories, and hundreds of corporate site surveys conducted by KRONE technicians, indicate that the physical layer can be a significant source of difficult-to-diagnose network problems. Field tests of corporate networks while they are running have repeatedly verified that network signals can be compromised by both poor cabling and out-of-specification active hardware. The result: corrupted Ethernet signals, resulting in dropped frames, and poor application performance. The KRONE technical papers: “The Effect of Errors on TCP Application Performance” and “Catching up with TrueNet” detail what happens to networks, and Transmission Control Protocol (TCP) performance in particular, when errors are present in a network. To summarize these in-depth papers: no matter how well your network is designed, or how much bandwidth you have, an error is an error to TCP — and errors slow down applications. The extent to which your physical network is a cause of errors has a tremendous amount of impact on how well your network is capable of operating. KRONE has found that many corporate users have error-causing problems hidden within their infrastructure, and they don’t even know it. KRONE has developed the TrueNet Structured Cabling System as a solution to this problem. The TrueNet System KRONE’s TrueNet Structured Cabling System is a complete physical layer consisting of cabling and connectivity components such as jacks, patch panels, termination blocks, horizontal cable and patch cords. The system was designed and manufactured specifically to ensure optimum LAN transmission performance. Further, KRONE is the first and only structured connectivity manufacturer to ensure physical layer performance in the active domain through our exclusive post-installation active testing program. The inherent advantages of post-installation active testing We are often asked why KRONE places so much emphasis on the active testing aspect of the TrueNet solution. There are a number of answers, some obvious, and some less so. A quality check of the cabling system — This might seem intuitive, but the quality check is not for the products themselves, it’s for the way they’re installed. This takes on two forms: the way the product is installed in your particular office space, with its own idiosyncrasies, and how well our certified installers performed the job. Your unique office environment — KRONE could claim that we do active testing in the factory or the lab to ensure “data throughput,” but what relationship does our laboratory have to your office environment? The fact is, the myriad conditions that can be present in real facilities just can’t be duplicated in the lab. What better test of how well it will work than testing what you actually have? The KRONE Certified Installer’s responsibility — KRONE Certified Installers are vigorously screened and trained to be the best in the industry. We demand more from our installers than any other company — KRONE doesn’t certify a TrueNet warranty until we’re satisfied the job was done correctly. We require our installers to send us passive test results for every node of your installation, and we check it to make sure it all passed. We give our installers more than twenty additional installation requirements over and above the standards — installation requirements that ensure that data throughput won’t be compromised by excessive noise, over-tightened cable fasteners, incorrect punch-downs and so forth. MANY PEOPLE BBEELLIIEEVVEE Network Troubleshooting Using TrueNet ™ Test Methodologies KRONE: 800-775-KRONE www.kroneamericas.com No part of this document may be reproduced without permission ©2001 KRONE ® Incorporated Given that office environments vary, and installation practices have a definite effect on the performance of the cabling system, the active test process serves as a final check that the installation was done properly, and the office itself doesn’t present any throughput-degrading challenges (such as external RF noise). A check of how your network actually runs — Another obvious benefit of KRONE ® active testing is that it’s an actual test of how well the as-configured network actually works. Since we wait until all the active components are installed before we do our testing, we have the opportunity to evaluate real traffic on your actual network. Traffic generators such as Smartbits ™ can simulate network activity and give us some information on the cabling system, but KRONE does not typically use traffic generators for the warranty verification for a couple of reasons. First, for reasons explained in “Catching up with TrueNet ™ ,” devices such as Smartbits are not a good indicator of how the real network will perform, and second, a traffic generator has its own network interface cards (NICs), so it isn’t really your network we would be testing. See what the active equipment is doing — As you’ll see later, active equipment has a variety of transmission characteristics that can be faulty in almost any NIC or port. Finding these faults is an added benefit of the active testing, and often the one that our customers find the most useful. Consider: a company moving offices from location A to B is almost certain to buy a new cabling system, but it’s very likely they will move all the computers, servers, hubs and switches with them. If any of those “imported” pieces of equipment have poor transmitters in them — you’ve just imported a problem into your brand new cabling system! The beauty of the KRONE warranty test methodology is that we can find these problems for the customer in the normal course of performing the warranty check. It’s essentially getting a “health check” on your active hardware for free. Making sure you got what you paid for — The suggestion that “any” Category 5e or 6 cabling system will perform flawlessly in the active domain so long as it meets the standards is simply not correct. In the “Catching up with TrueNet” paper, KRONE shows two Category 5e cabling systems, one TrueNet, the other “mix-and-match” that have radically different error rates. In fact, the ”mix- and-match“ solution dropped as many as 148 frames per second, compared with the KRONE solution, which only dropped one frame in 12 minutes. What does KRONE’s bit error warranty entail — The bit error aspect of the KRONE warranty has been the subject of many questions, so we’d like to clarify a point or two. The nature of the warranty is to ensure that the cabling system will not cause bit errors that degrade performance; provided the active hardware in use is operating within the specifications defined by IEEE 802.3xx. The operative terms here are “cabling system” and “degrade performance.” As shown in the KRONE white paper “Catching Up With TrueNet,” a TrueNet Category 5e system performs dramatically different from the alternative Category 5e system tested. In that case, the TrueNet Cabling System only clocked one bit error in nearly 12 minutes — and that error could have been due to the switch or the NIC! The alternative cabling system had four errors per second or worse, using the exact same port and NIC. The critical thing to understand here is the time factor. KRONE samples actual traffic on the network and pinpoints possible problems with the active testing program. In doing so, we ensure that operating bit error rates in the installed system are 10 -10 (0.000000001%) or better. As a function of elapsed time, this error rate is so low that the effect on TCP (and applications, by extension) is imperceptible to the user. TrueNet System active testing Let’s take a look at some of the real-world networks that KRONE has encountered in site surveys. First, however, it’s instructive to see what a well-matched system should look like. In Figure 1, we see an “impedance over distance” trace, which basically shows the electrical signature of the cabling channel over its distance. The meter scale along the X-axis shows us this channel is approximately 81 meters long. The electrical trace is smooth and all pairs line up on top of each other. This is a good channel. Figure 2 shows the same channel in the frequency (MegaHertz) domain. This could never be a precisely smooth trace, but the lines should be as compact as possible, without any evidence of cyclical oscillation. Figures 1 and 2 are a TrueNet cabling channel. Now, we’ll also look at some characteristics of an active Ethernet signal that also have a bearing on how well signals are transmitted. They are the parameters that define the shape of the transmitted signal, and include rise time/fall time, amplitude and jitter. 2 An obvious benefit of KRONE active testing is that it’s an actual test of how well the as-configured network actually works. KRONE: 800-775-KRONE www.kroneamericas.com No part of this document may be reproduced without permission. ©2001 KRONE ® Incorporated TrueNet ™ System characteristics Figure 1 shows the impedance of a TrueNet structured cabling channel over the distance of the entire channel length. All the components in the channel: patch cords, jacks, patch panels, interconnect, cross-connect, horizontal cable and so forth, appear on this trace, but it is nearly impossible to tell where the individual components are located. All four cable pairs are impedance matched throughout the length of the channel. In the same channel, impedance is charted against frequency (in MegaHertz) to show that the impedance holds a tight band at 100 ± 15 ohms for the critical frequency range of 1–125 MHz where the energy of Ethernet signals is concentrated (Figure 2). Beyond the channel’s impedance characteristics, however, the following active test characteristics are important to proper network operation: network load, jitter, rise/fall time, minimum voltage/amplitude, interference, CRC errors, alignment fragments, interframe gap and oversized/undersized packets. Within this document, we’ll examine three active test characteristics: rise/fall time, amplitude and jitter. Rise and fall time — These characteristics are important to system performance, as synchronization requires “change of state” to occur within a specified time frame. Even if the signal reaches proper amplitude — but too slowly — the signal is misinterpreted (Figure 3). For example, TrueNet Warranty Certification Tests run at a large, nationwide law firm showed that some sections of their newly-installed network were running slowly. The problem: the 100BASE-T port on a brand new switch was out of compliance for both rise time and fall time (Figures 4 and 5). Imagine if this had been the connection to a server! 3 Nanoseconds Voltage Rise Time Fall Time Rise and fall time is the length of time, in nanoseconds, that it takes for a signal to rise or fall from one state to another, signaling a “one.” Figure 3: Rise and fall time. 7.8 6.0 4.3 2.5 0.8 Volts IEEE LIMIT Time (Nanoseconds) GOOD WARNING ERROR Figure 4: Rise time. 0 9 18 27 36 45 54 63 72 81 90 Distance (Meters) 40 50 60 70 80 90 100 110 120 130 140 Impedance (Ohms) KRONE IMPEDANCE MATCHED CHANNEL —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 1: A TrueNet matched impedance channel. 0 26 52 78 104 130 156 182 208 234 260 Frequency (MHz) 40 50 60 70 80 90 100 110 120 130 140 Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 2: Frequency trace of a TrueNet channel. 7.8 6.0 4.3 2.5 0.8 IEEE LIMIT Time (Nanoseconds) GOOD WARNING ERROR Volts Figure 5: Fall time. Rise and fall time is the length of time, in nanoseconds, that it takes for a signal to rise or fall from one state to another, signaling a “one.” KRONE: 800-775-KRONE www.kroneamericas.com No part of this document may be reproduced without permission. ©2001 KRONE ® Incorporated Amplitude — The amplitude of a wave (Figure 6) is equivalent to the height of the physical wavelength — also signaling to the active device a “change in state” corresponding to a one or zero. If the amplitude is not within the specified range, errors can occur. Using actual test data, we “see” an active device that is well within the specified limits (Figure 7, yellow lines). The NIC is barely within compliance, however, and over time may drift out of specification (Figure 8). Jitter — In yet another installation, the 10BASE-T card shows significant instability in meeting the IEEE jitter specification (Figure 9). Over time, this card may begin to emit signals not within specifications. How are system errors found? The previous information gives some idea of the type of errors that the TrueNet ™ warranty testing brings to light, but how are these errors actually found? First, the entire network must be polled for errors. There are various products that poll SNMP (Simple Network Management Protocol) reports for errors. Alternatively, specific nodes that are known to be problems can be polled directly. By attaching a diagnostic device to problem nodes, KRONE ® technicians are able to capture specific error events and filter them by type. Experience shows that certain errors tend to be attributable to cabling problems, and others to poorly performing active equipment. Of course, once error events are detected on a specific node, it is relatively simple to determine the health of the active devices. If the active devices check out, then it is time to analyze the cabling traces for problems. Figure 10 shows a series of errors. In this particular test situation, we are seeing a number of fragment errors, depicted on the report as “Jams” or “Runt” packets. These packets are not complete and cannot be interpreted by the receiving end. At the extreme bottom of the chart, we see two errors that indicate a wrong value in the destination prefix. This means that the “addressee” is not known. Again, the packet cannot be used if it’s not known where to send it. 4 Amplitude signals a “change in state” to the active device. Jitter relates to the stability of the NIC. Amplitude Wavelength Figure 6: Sine wave amplitude. 10.0 7.5 5.0 2.5 0.0 Time (Nanoseconds) GOOD WARNING ERROR Volts Figure 7: This active device from an actual installation shows amplitude well within the specified limits (yellow lines). 4 3 2 1 0 Time (Nanoseconds) GOOD WARNING ERROR Volts Figure 8: This NIC is barely within compliance, and overtime may drift out of specification. 22 11 0 -11 -22 Volts Time (Nanoseconds) GOOD WARNING ERROR Figure 9: Significant instability in meeting the IEEE jitter is apparent in this 10BASE-T card. KRONE: 800-775-KRONE www.kroneamericas.com No part of this document may be reproduced without permission. ©2001 KRONE ® Incorporated The exclusive TrueNet ™ test methodology extends to the active devices in use, evaluating if NICs, hubs and switches are performing within IEEE specifications. The end result is a LAN that is proven to transmit data efficiently, allowing network managers to concentrate on other concerns. NIC concerns In site after site, we have noticed a tremendous variation in the performance of NICs. The rule of thumb we’ve found is: once a NIC becomes marginal, it never gets any better. And some NICs are marginal right out of the box — in fact, to some users it has become commonplace to view the NIC as an expendible resource. Some companies are even known to keep dozens of “cheap” NICs around, replacing them constantly, at the first sign of trouble. We also have found that the probability of finding a marginal NIC has nothing to do with the brand or expense of the card. Inexpensive and expensive brands alike are just as likely to fail; and a weak NIC (Figures 11, 12 and 13) has very little chance of successful transmission when the poorly transmitted 5 8.0 6.5 5.0 3.5 2.0 Time (Nanoseconds) GOOD WARNING ERROR Volts Figure 11: Rise time of a weak NIC. 8.0 6.5 5.0 3.5 2.0 Time (Nanoseconds) GOOD WARNING ERROR Volts Figure 12: Fall time of a weak NIC. Figure 10: This screen shot shows a series of errors, depicted in the “Failure Type” column. 22 11 0 -11 -22 Volts Time (Nanoseconds) BORDER LINE JITTER GOOD WARNING ERROR Figure 13: Jitter characteristics of a weak NIC. A weak NIC has very little chance of successful transmission when the signal must also navigate system mismatches. KRONE: 800-775-KRONE www.kroneamericas.com No part of this document may be reproduced without permission. ©2001 KRONE ® Incorporated signal reaches the closet (and must then navigate the usual system mismatches in its weakened/attenuated state). This is why we so often see 10/100 nodes auto-negotiate down to 10 Mb/s (because they cannot maintain the transmission at 100 Mb/s). Misguided MIS managers often attempt to turn off auto-negotiation to prevent this from occurring, the consequence being a virtual meltdown of the network — nothing can get through at all. TruePatch ™ Patch Cords test results TruePatch Cords are a key component to the TrueNet ™ Structured Cabling System. They provide a vital system upgrade and solve a problem found in many networks — unmatched, low performance/low reliability patch cords. Research has shown that even one marginal patch cord can substantially slow down an entire network. But the overall performance of the network can be significantly improved just by replacing the existing patch cords with TruePatch Patch Cords. Figures 14, 15, 16 and 17 serve as examples of how TruePatch Cords can advance the performance of a network. These examples are not laboratory created simulations of theoretical problems, they are based on real, active domain tests conducted at various corporate sites. An electronic components manufacturer — Tests showed that this manufacturer has good horizontal cable, but a poorly matched patch cord which has a much lower impedance than the horizontal cable (Figure 14). For such a seemingly minor part of the entire channel, that patch cord can cause big problems for data transmission. Notice how the patch cord causes the impedance versus frequency chart to drop out on the low end of impedance (Figure 15). A TruePatch cord added to the channel is almost a perfect match (note the green pair still spikes in the jack — Figure 16). In this case, a TruePatch cord with the existing horizontal cabling yields a good trace for impedance versus frequency. A TruePatch cord makes the difference between passing and failing (Figure 17). A top US airline — This channel was one of the worst we had ever seen. The user on this node complained that his computer was excruciatingly slow when down- loading files off the network. We suspected an enormous impedance mismatch and a wide difference in the impedance between pairs to be the culprit (Figure 18). The next chart shows this channel to be way out of 6 036912151821242730 40 50 60 70 80 90 100 110 120 130 140 Distance (Meters) IMPEDANCE USING A TRUEPATCH PATCH CORD Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 16: A TruePatch cord added to the channel corrects the problem. 0 26 52 78 104 130 156 182 208 234 260 40 50 60 70 80 90 100 110 120 130 140 Frequency (MHz) 10BASE-T 100BASE-T Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 17: The addition of a TruePatch cord can be the difference between meeting or failing the spec. For such a seemingly minor part of the entire channel, a bad patch cord can cause big problems for data transmission. 0 26 52 78 104 130 156 182 208 234 260 40 50 60 70 80 90 100 110 120 130 140 Impedance (Ohms) Frequency (MHz) 10BASE-T 100BASE-T —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 15: Patch cord causes big problems for data transmission. 0 4 8 12 16 20 24 28 32 36 40 40 50 60 70 80 90 100 110 120 130 140 Impedance (Ohms) Distance (Meters) IMPEDANCE MISMATCH OF THE PATCH CORD, THE BLOCK AND THE CABLE —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 14: Good horizontal cable with a poorly matched patch cord. KRONE: 800-775-KRONE www.kroneamericas.com No part of this document may be reproduced without permission. ©2001 KRONE ® Incorporated specification. It took this user eight minutes to download a large PowerPoint ® file over this node (Figure 19). Simply replacing the patch cord at the computer cleans up the channel quite a bit; but will it bring the frequency chart into compliance (Figure 20)? As you can see, the frequency curve isn’t completely normal, but the patch cord made a big difference nonetheless. The same file that took eight minutes to download, now took only two minutes. Of course, actual results on other networks will vary, but this is a compelling example of the value of good infrastructure (Figure 21). A software and engineering firm — Sometimes the TruePatch ™ Cord will smooth out network problems, but other system components may also need to be replaced. Tests at this firm showed that the patch cord was ill-matched to the horizontal cable (Figure 22). Note in particular how the green and brown pairs differ in impedance from each other. The impedance spikes occurring at five meters into the run (viewing left to right) are the poorly matched interface between the plug on the patch cord and the jack. Simply replacing the existing patch cord with a TruePatch cord yields a noticeable improvement in the trace. Note, however, that since the jacks were not part of a matched system, the same spike occurs at the plug/jack interface (Figure 23). 7 01020304050607080 40 60 80 100 120 140 Distance (Meters) IMPEDANCE MISMATCH OF THE PATCH CORD, THE PANEL AND THE CABLE IMPEDANCE MISMATCH OF THE CABLE CONDUCTORS Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 18: A channel with an impedance mismatch and mismatched cable pairs. -20 0 20 40 60 80 100 120 60 70 80 90 100 110 120 130 140 150 160 Frequency (MHz) <<10BT 100BT Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 19: Viewed in the frequency domain, it is apparent that the channel is way out of specification. 0 10 20 30 40 50 60 70 80 90 40 60 80 100 120 140 Distance (Meters) IMPEDANCE IMPROVEMENT USING A TRUEPATCH PATCH CORD Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 20: The same channel with a TruePatch cord. -20 0 20 40 60 80 100 120 50 60 70 80 90 100 110 120 130 140 150 Frequency (MHz) <<10BT 100BT IMPROVEMENT USING A TRUEPATCH PATCH CORD Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 21: The addition of TruePatch greatly improves channel performance. 0 5 10 15 20 25 30 35 40 45 50 40 60 80 100 120 140 Distance (Meters) IMPEDANCE MISMATCH OF THE PATCH CORD, THE PANEL AND THE CABLE IMPEDANCE MISMATCH OF THE CABLE CONNECTORS Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 22: Patch cord is ill-matched to horizontal cables. 0 4 8 12 16 20 24 28 32 36 40 40 50 60 70 80 90 100 110 120 130 140 Distance (Meters) IMPEDANCE IMPROVEMENT USING A TRUEPATCH PATCH CORD Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 23: Replacement of patch cord yields a noticeable improvement. Replacing a patch cord with a TruePatch cord can smooth out network problems. KRONE: 800-775-KRONE www.kroneamericas.com No part of this document may be reproduced without permission. ©2001 KRONE ® Incorporated KRONE and TrueNet are trademarks of KRONE ® Incorporated. All other trademarks are property of their respective owners. KRONE ® Incorporated North America Headquarters 6950 South Tucson Way Englewood, CO 80112-3922 Telephone: (303) 790.2619 Toll-Free: (800) 775.KRONE Facsimile: (303) 790.2117 www.kroneamericas.com The original patch cord causes the channel’s impedance over frequency to drop below 85 ohms at lower than 100 MHz, meaning potentially serious data transmission problems (Figure 24). The TruePatch ™ cord in the same channel smooths out the frequency trace somewhat, actually bringing most of the trace into compliance. However, the lack of fine tuning throughout the whole channel means that even the addition of the TruePatch cords will not completely eliminate throughput problems (Figure 25). A benefits administration company — This last installation example, occurring at a benefits administration company, shows huge mismatches and inconsistencies, particularly with cross-connect blocks and poorly installed cable. This customer with a 10BASE-T network was considering an upgrade to 100BASE-T (Figure 26). TruePatch cords aren’t able to overcome the cross- connect block, but they do manage to smooth out the trace somewhat (Figure 27). This node will never run 100BASE-T effectively, as the massive oscillations will cause tremendous signal degradation (Figure 28). The TruePatch cord makes some difference, but not enough. Our recommendation: don’t waste money on 100BASE-T active equipment without first fixing the infrastructure (Figure 29). 8 0 4 8 12 16 20 24 28 32 36 40 Distance (Meters) 40 50 60 70 80 90 100 110 120 130 140 Impedance (Ohms) IMPEDANCE MISMATCH OF THE PATCH CORD, THE BLOCK AND THE CABLE HARSH BENDS AND OVER TIGHTENED CABLE TIES TYPICAL CHARACTERISTIC OF OVER PULLING TENSION IMPEDANCE MISMATCH OF THE CABLE, THE STATION OUTLET AND THE PATCH CORD —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 26: Without TruePatch, this channel has huge mismatches and inconsistencies. 0 26 52 78 104 130 156 182 208 234 260 Frequency (MHz) 40 50 60 70 80 90 100 110 120 130 140 Impedance (Ohms) 10BASE-T 100BASE-T —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 28: This node will not run 100BASE-T effectively. 0 4 8 12 16 20 24 28 32 36 40 Distance (Meters) 40 50 60 70 80 90 100 110 120 130 140 REDUCED IMPEDANCE MISMATCH OF THE BLOCK AND THE CABLE USING A TRUEPATCH PATCH CORD REDUCED REFLECTION POINTS REDUCED IMPEDANCE MISMATCH Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 27: With TruePatch, the traces smooth out. 0 26 52 78 104 130 156 182 208 234 260 40 50 60 70 80 90 100 110 120 130 140 Frequency (MHz) 10BASE-T 100BASE-T Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 29: The TruePatch cord helps this node, but cannot remedy all the infrastructure problems. Check Your Infrastructure First Armed with this kind of evidence, we would hope that most companies would heed our warning and look first at network infrastructure before investing in more software, active equipment and/or more bandwidth. An active system test is a completely plausible way to diagnose network problems and, as evidenced, it can go a long way toward pointing out some network performance deficiencies. 0 26 52 78 104 130 156 182 208 234 260 Frequency (MHz) 40 50 60 70 80 90 100 110 120 130 140 Impedance (Ohms) 10BASE-T 100BASE-T —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 24: Original patch cord causes the impedance to drop. 0 26 52 78 104 130 156 182 208 234 260 40 50 60 70 80 90 100 110 120 130 140 Frequency (MHz) 10BASE-T 100BASE-T Impedance (Ohms) —— —— PAIR 1 —— —— PAIR 2 —— —— PAIR 3 —— —— PAIR 4 Figure 25: The TruePatch cord helps to smooth out the frequency trace. . benefit of KRONE active testing is that it’s an actual test of how well the as-configured network actually works. KRONE: 80 0-7 75 -KRONE www.kroneamericas.com No. smooth out network problems. KRONE: 80 0-7 75 -KRONE www.kroneamericas.com No part of this document may be reproduced without permission. 2001 KRONE ® Incorporated KRONE