Even if your cable installer didn't use cheap cable or neglected to connect half of the wires in the cable, other Cat-5 issues could cause problems when you use Gigabit Ethernet. For example, 10/100-Mbps Ethernet standards require that no cable run exceed 100 meters. However, Ethernet and Fast Ethernet tend to be very forgiving when cable lengths are exceeded, so many organisations ignore the limit. Ignoring the 100-meter limit will come back to bite you when you implement Gigabit Ethernet. Likewise, I've seen many Ethernet and Fast Ethernet networks in which Cat-5 cable segments are spliced together. While this isn't supposed to work, it does when they're spliced well. But splices tend to cause big problems for Gigabit Ethernet. Before implementing Gigabit Ethernet, I strongly recommend making sure that your cabling is up to the job. I suggest running three types of tests on your cabling. First, run a continuity test to verify that all eight wires are properly connected. Next, run a far-end crosstalk test. Finally, run a return signal loss test. If your cabling passes all three tests, the cable is adequate for Gigabit Ethernet use. Network cabling basics
What about Category 5e and Category 6 cabling? Learn the latest on current and emerging network cable standards by reading the article "Know the facts about network cabling." Speeding things up
As you can see, the condition and length of your Cat-5 cable can greatly affect your network's performance. One way of getting around the problems caused by poor cable conditions or longer cable runs is to use fiber-optic cable instead of copper cable. Gigabit Ethernet is designed to work with either fiber or copper cable. However, merely switching to fiber-optic cable won't solve all your problems. Fiber-optic cable is just as susceptible to problems as copper cable. Although it's true that fiber is more secure than copper and supports higher data speeds and longer runs, it's also much more delicate than copper. Things like excessive epoxy on the cable ends, poorly made splices, too many splices, cable damage, and excessive cable bends can dramatically slow or even stop network traffic flowing through fiber. I personally prefer using fiber over copper in many environments, but even using good quality, properly installed fiber will only help you so much. The reason is that most computers are incapable of producing packets at gigabit rates. Currently, most PCs produce packets at the CPU level and then pass them through the PCI bus to the NIC and across the network. There are processors that can produce packets at gigabit speeds, but it's important to remember that most of the time, your processors are busy doing things other than producing packets. For example, in addition to producing packets, a server's processor is managing memory, running services, and maintaining the user interface. Windows 2000 is more efficient than Windows NT and can produce packets faster, but this is still typically not enough to utilise a gigabit NIC's full potential. There are several new technologies that will help you get the most out of Gigabit Ethernet and may soon allow 10- or even 100-gigabit connections. The PCI-X bus and other new technologies
One such technology is the new PCI-X bus, which is similar to the PCI bus but isn't as bandwidth-intensive when used in conjunction with PCI-X cards. This means that when a PCI-X bus and a PCI-X-based NIC are in use, packets can flow between the CPU and the NIC much more quickly than they could on a purely PCI machine. Although faster bus speeds will usually allow a gigabit connection to utilise its full potential, other new technologies are at work. Some companies are developing NICs that have built-in microprocessors. The idea is to have a CPU dedicated to the sole task of generating packets. Because this CPU is integrated into the card, it's guaranteed to be fast enough to produce packets at speeds for which the card is intended (1, 10, or 100 Gbps). Still another experimental technology is bonding. Several NIC manufacturers have prototype NICs with multiple onboard fiber-optic ports. These NICs use several cables at once for parallel traffic flow, and they have an onboard microprocessor that does IP processing at the card level.