Information Technology Reference
In-Depth Information
works. As the data signal passes from any connected device to the hub or switch, a
process called “repeating” in Ethernet reconstitutes the signal.
Some network topologies are a hybrid of the basic topologies. For example, in
Token-Ring, the “ring” is normally cabled like a “star,” but the arms of the star are
interconnected at the Token-Ring hub (MSAU) in the TR so as to form the ring. As
you can imagine, each topology and LAN standard has its fans, as well as its detrac-
tors. We will stay away from that contest, except to point out when a wiring method
can be used for several topologies.
In this chapter, we will concentrate only on current technologies including
twisted-pair and fiber-optic Ethernet and Token-Ring. In Appendix B, we will cover
the legacy topologies and the lesser technologies, including Ethernet coax, Arcnet,
100VG-AnyLAN, isochronous Ethernet, AppleTalk, Local Talk, FDDI, and ATM
(as a local area networking topology, rather than a wide-area protocol). You may
encounter some of these older or less-common LAN topologies, and some of them,
such as FDDI and ATM, are still in use for many applications, although none are
generally considered for new cabling installations.
The introduction of twisted-pair wiring into standard Ethernet networking ushered in a
new age of network connectivity. For some time, frustrated users had been experiment-
ing with thinnet-to-twisted-pair baluns in order to use existing telephone wire for net-
work links. Several manufacturers even introduced proprietary network adapters and
hubs for twisted-pair Ethernet. Eventually, a standard was fashioned, under the umbrella
of the IEEE 802.3, to deploy a new twisted pair Ethernet topology called
10BaseT
.
This new standard and its higher-speed successors were very well accepted and
robust, indeed. They have been so successful that they have virtually eliminated the
installation of new 10Base5 and 10Base2 networks. The need to specify a system of
universal telecommunications cabling that would allow the proper operation of
10BaseT (originally) gave rise to a series of new cable, wiring, and component stan-
dards that eventually resulted in an industry standard called EIA/TIA-568.
Nowadays, that original 10 Mbps Ethernet is beginning to seem very slow.
Ethernet networking has taken a jump first to 100 Mbps, then to 1000 Mbps (1
Gbps), and now even to 10 Gbps over twisted-pair cable. Fortunately, the standards
committees have kept pace with these developments and have released 100 Mbps,
1000 Mbps, and 10 Gbps standards for network adapters, hubs, switches, cable,
and wiring components.
We will cover classic copper (twisted-pair) 10BaseT topology first, because it is
essentially identical to 100/1000BaseT in topology. In fact, combination network cards
