Hardware Reference
In-Depth Information
Formaximumeconomy,NICsandnetworkcablesmustmatch,althoughmediaconverters
can interconnect networks based on the same standard, but using different cable.
Network Cables for Wired Ethernet
Originally, all networks used some type of cable to connect the computers on the network
to each other. Although various types of wireless networks are now on the market, many
office and home networks still use twisted-pair Ethernet cabling. Occasionally you might
still find some based on Thick or Thin Ethernet coaxial cable.
Thick and Thin Ethernet Coaxial Cable
The first versions of Ethernet were based on coaxial cable. The original form of Ethernet,
10BASE-5, used a thick coaxial cable (called
Thicknet
) that was not directly attached to
the NIC. A device called an
attachment unit interface (AUI)
ran from a DB-15 connector
on the rear of the NIC to the cable. The cable had a hole drilled into it to allow the “vam-
piretap” tobeconnected tothecable. NICsdesigned forusewith thick Ethernet cable are
almost impossible to find as new hardware today.
10BASE-2EthernetcardsuseaBNC(Bayonet-Neill-Concelman)connectorontherearof
the NIC. Although the thin coaxial cable (called
Thinnet
or
RG-58
) used with 10BASE-2
Ethernet has a bayonet connector that can physically attach to the BNC connector on the
card, this configuration is incorrect and won't work. Instead, a BNC T-connector attaches
to the rear of the card, allowing a Thin Ethernet cable to be connected to either both ends
of the T (for a computer in the middle of the network) or to one end only (for a computer
at the end of the network). A 50-ohm terminator is connected to the other arm of the T
to indicate the end of the network and prevent erroneous signals from being sent to other
clients on the network. Some early Ethernet cards were designed to handle thick (AUI/
DB-15), thin (RG-58), and UTP (unshielded twisted pair) cables. Combo cards with both
BNCand8P8C(RJ-45)connectorsarestillavailableonthesurplusequipmentmarketbut
can run at only standard 10Mbps Ethernet speeds.
Figure 17.5
compares Ethernet DB-15 to AUI, BNC coaxial T-connector, and 8P8C
(RJ-45) UTP connectors, and
Figure 17.6
illustrates the design of coaxial cable.
Figure 17.5
An Ethernet network card with Thick Ethernet (DB-15), Thin Ethernet (RG-58 with T-con-
nector), and UTP (8P8C/RJ-45) connectors.
