Hardware Reference
In-Depth Information
1,000Mbps (Gigabit Ethernet). Most desktop and even laptop systems now incorporate
Gigabit Ethernet. In the future we will likely see 10 Gigabit Ethernet (also known as 10G
Ethernet)appearinginPCs.10GEthernetrunsat10,000Mbpsandisusedprimarilyinen-
terprise data centers and servers.
Note
Throughout the remainder of this chapter, be aware that discussion of older Ethernet solu-
tions (such as those using Thicknet or Thinnet) as well as alternative networks (such as
Token-Ring) are only included for reference. You will usually encounter those technologies
only when working on older, existing networks. New network installations today normally
use Gigabit, Fast, or Wireless Ethernet.
Fast Ethernet
Fast Ethernet requires adapters, hubs, switches, and UTP or fiber-optic cables designed
to support its rated speed. Some early Fast Ethernet products supported only 100Mbps,
but almost all current Fast Ethernet products are combination devices that run at both
10Mbpsand100Mbps,enablingbackwardcompatibility witholder10MbpsEthernet net-
work hardware.
Note
Some specifications say that Fast Ethernet supports 200Mbps. This is because it normally
runs in
full-duplex mode
(sends/receives data simultaneously), which gives it an effective
speed of 200Mbps with both directions combined. Still, the throughput in any one direction
remains the same 100Mbps. Full-duplex operation requires that all hardware in the connec-
tion,includingadaptersandswitches,becapableofrunninginfull-duplexandbeconfigured
to run in full-duplex (or automatically detect full-duplex signals).
Both the most popular form of Fast Ethernet (100BASE-TX) and 10BASE-T standard
Ethernet use two of the four wire pairs found in UTP Category 5 cable. (These wire pairs
are also found in Cat 5e, Cat 6, and Cat 6a cable.) An alternative Fast Ethernet standard
called 100BASE-T4 uses all four wire pairs in UTP Category 5 cable, but this Fast Ether-
net standard was never popular and is seldom seen today.
Gigabit Ethernet
Gigabit Ethernet also requires special adapters, hubs, switches, and cables. When Gigabit
Ethernetwasintroduced,mostinstallationsusedfiber-opticcables,buttodayitisfarmore
common to run Gigabit Ethernet over the same Category 5 UTP cabling (although better
Cat 5e/6/6a is recommended) that Fast Ethernet uses. Gigabit Ethernet for UTP is also re-
ferred to as 1000BASE-T.
