Guide to Network Cabling
Fundamentals
Chapter 3
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Chapter 3 - Cables and the Cabling
Infrastructure
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Identify the various types of cable and their
characteristics
Compare cable types and characteristics
Identify and differentiate between the various
network topologies
Create an effective network design
Identify which network elements you must include in
your documentation
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Cable Types and Characteristics
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When selecting telecommunications system cable,
the system needs must be matched with the
characteristics of the cable
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The three basic cable types are coaxial, twisted-pair, and
fiber-optic
An alternative to cable is wireless technologies, which
transmit signals through the atmosphere
The five basic cable characteristics are: throughput and
bandwidth; cost; size and scalability; connectors; and
noise immunity
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Cable Types and Characteristics
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Cable characteristics:
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Throughput is the amount of data that a cable can
transmit during a given period and is measured in
megabits per second, or Mbps
Throughput potential is determined by the physical
nature of the cable
Bandwidth is the measure of the difference between the
highest and lowest frequencies that the media can
transmit, it is measured in hertz (Hz)
Bandwidth is directly related to throughput, and the
higher the bandwidth, the higher the throughput
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Cable Types and Characteristics
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Cable characteristics (cont.):
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Cost for different types of cable varies depending on
available hardware, installation, transmission rate, and
the obsolescence potential of the medium
Size and scalability is determined by the maximum
nodes per segment, the maximum length per segment,
and the maximum network length
Connectors are specific based on the type of cable used
and can affect the cost of installation
Noise immunity is the cable’s ability to deter noise (EMI
and RFI) that can distort data signals
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Cable Types and Characteristics
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Cable types:
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Coaxial cable, also called coax, consists of a central
copper core surrounded by an insulator, braiding, and a
plastic jacket
Coax has a high resistance to interference from noise
due to its insulation and protective braiding
Coax carries signals farther than twisted-pair, but is
more expensive and supports a lower throughput
A key specification for coax is impedance, or its measure
of resistance to alternating current flow; each unit of
resistance is expressed as an ohm
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Cable Types and Characteristics
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Cable types (cont.):
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Twisted-pair is the most common form of cabling used
on LANs today; it is relatively inexpensive, flexible, and
easy to install; but it does not span as great a distance
as coax
Twisted-pair can easily accommodate a variety of
network topologies, and can handle faster transmission
rates than coax
Twisted-pair, because of its flexibility, is more prone to
physical damage than coax
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Cable Types and Characteristics
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Cable types (cont.):
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Twisted-pair consists of insulated copper wires, with 0.4
to 0.8 mm diameter, twisted in pairs around each other
and encased in a plastic coating
The twists in a twisted-pair cable reduce the effect of
crosstalk, the infringement of the signal from one wire
pair on another wire pair’s signal; crosstalk is measured
in decibels (dB), a measurement unit of signal strength
of a sound’s intensity
The number of twists per inch determines how resistant
the pair will be to noise
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Cable Types and Characteristics
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Cable types (cont.):
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Shielded twisted-pair (STP) consists of individually
insulated twisted pairs surrounded by a metallic
shielding that must be grounded
Unshielded twisted-pair (UTP) consists of insulated pairs
of wires encased in a plastic sheath; it is less expensive
and less resistant to noise than STP
Screened twisted-pair (ScTP) consists of insulated pairs
of wires contained in a full foil laminate shield; it offers
superior immunity to radio frequency fields and reduced
crosstalk
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Cable Types and Characteristics
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Cable types (cont.):
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Fiber-optic cable, also called fiber, contains one or more
glass fibers in its core; around the fibers is a layer of
glass, called the cladding; over the cladding is layer of
plastic and a braiding of kevlar
Data is transmitted by converting electrical signals at the
sending end into optical signals, which are then
transmitted through the fibers by light pulses
Fiber comes in single-mode, which carries a single mode
of light to transmit data; and multimode, which can carry
hundreds of thousands of
modes of light simultaneously
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Comparing Cables and Their
Characteristics
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Cable comparisons:
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ThickNet (10Base5) is called ThickWire Ethernet
ThickNet’s maximum transmission rate of 100 Mbps and
transmits using baseband, a method that allows only one
signal to be transmitted at a time
ThickNet is less expensive than fiber, but much more
expensive than ThinNet or twisted pair
ThickNet requires a vampire tap to connect to a
transceiver, and a drop cable to connect devices
ThickNet has the highest resistance to noise and allows
data to travel for greater distances
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Comparing Cables and Their
Characteristics
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Cable comparisons (cont.):
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ThinNet (10Base2) is called thin Ethernet
ThinNet has a maximum transmission rate of 10 Mbps
and transmits using baseband
ThinNet is less expensive than ThickNet or fiber, but
more expensive than twisted pair
ThinNet uses BNC and BNC/T connectors to connect
wires to devices
ThinNet is more resistant to noise than twisted-pair and
its maximum segment length is 185 m
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Comparing Cables and Their
Characteristics
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Cable comparisons (cont.):
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STP and UTP can transmit data at 10 Mbps; CAT5 UTP
at 100 Mbps; enhanced CAT5 and CAT6 can transmit
data at 1000 Mbps
Costs of STP, ScTP, and UTP vary; STP and ScTP are
usually more expensive than UTP
All twisted-pair cables use 8-pin RJ-45 connectors
STP and ScTP are more resistant to noise than UTP and
the maximum segment length for STP and UTP is 100
m; for ScTP it is 98 m
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Comparing Cables and Their
Characteristics
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Cable comparisons (cont.):
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Fiber was used primarily as a backbone cable until
recently and can transmit data at 1 Gbps
Fiber is one of the most expensive cables; network
communication devices, such as NICs and hubs, can
cost more than those for other networks
Fiber cabling uses many types of connectors; the
industry standards are the ST and SC; and MT-RJ small
form factor connectors
Fiber is immune to both EMI and RFI and the maximum
segment length is 100 m
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Comparing Cables and Their
Characteristics
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Cable comparisons (cont.):
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Wireless networking refers to computers that
communicate using standard networking protocols, but
without the use of cabling to connect devices
The computers transmit data by means of wireless
signals produced by infrared (requiring equipment to be
in a direct line of sight) or radio waves
Wireless networks require installation of NICs with builtin antennas and uses access points as hubs
Wireless networks currently transmit data at
approximately 11 Mbps
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Network Topologies
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There are two types of network topologies:
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Physical topology is the physical layout of the network,
including cable and device configuration
Logical topology refers to the method used to
communicate between the devices
It is important to understand the physical topology before
designing networks, because they can affect the logical
topology chosen, how the building is cabled, and what
kind of media is used
Physical topologies are classified according to three
geometric shapes: bus, ring and star
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Network Topologies
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Physical topologies:
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Bus consists of a single cable that connects all the
nodes of a network without intervening connectivity
devices, and requires a terminator at each end
The single cable is called the bus and supports one
channel, where each node shares total capacity
Bus advantages: easy to install and add devices;
requires less cable; less expensive
Bus disadvantages: requires terminators; entire network
shuts down if the cable breaks; difficult to troubleshoot;
limit is about 10 connections
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Network Topologies
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Physical topologies (cont.):
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Ring is where each node is connected to the two nearest
nodes, effectively forming a circle
Data is transmitted in one direction around the ring, and
is typically done so using token passing
The ring is used by Token Ring and FDDI networks
Ring advantages: no network collisions; each node
functions as a repeater; less cable required
Ring disadvantages: Single malfunctioning node can
disable entire network; not flexible or scalable;
modifications requires network shutdown
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Network Topologies
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Physical topologies (cont.):
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Star is where each node is connected through a central
device, such as a hub
All nodes transmit data to the hub, which then
retransmits the data to the destination node
Star advantages: a break in the cable does not shut
down the network; higher reliability; easier
troubleshooting; no terminators required
Star disadvantages: uses more cable; hubs are more
expensive than terminators; hub failures take down
entire LAN segments
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Network Topologies
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Physical topologies (cont.):
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Mesh is where all devices share many redundant
interconnections with each node; full-mesh means every
node is interconnected, partial-mesh is where some
nodes are connected to one or two others
Mesh advantages: if one connections fails, data can be
redirected; higher level of security; easy troubleshooting;
greater stability and reliability
Mesh disadvantages: uses much more cable; more
expensive to install; difficult to install and configure on
very large networks
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Creating an Effective
Network Design
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Steps for ensuring flexible and solid network design
that meets customer expectations:
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Assessing functional requirements includes listing tasks to
be automated and updated; determining which business
applications will be used and how; identify needs such as
e-mail, Internet access, etc.
Sizing the network includes establishing the number of
users and their intended use; calculate user community
growth and network capacity growth
Connectivity involves defining external connections;
Internet requirements; assessing bandwidth
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Creating an Effective
Network Design
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After prerequisites, decisions are required for the
following network design issues:
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Network type, including Ethernet, ATM, Token Ring
Physical network, including cabling, faceplates, and other
components of the basic infrastructure
Network communications equipment, such as hubs
Network operating system, such as Windows/Novell
Workstations, considering the hardware/software
Network server hardware and data backup hardware and
software
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Network Elements You Need to
Document
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Network documentation needs:
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The first section describes the network: topology, network
architectures, operating systems, device and user counts,
and contact information
The next section is used most frequently and it defines the
physical layout of the network cabling; every time the
network requires modification, this section will be consulted
and modified
Also include in the documentation: equipment room items;
the internetworking devices; device specifications, such as
port usage, physical and logical addresses, model and
serial numbers
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Chapter Summary
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Cabling is the basic framework of a solid network
foundation. To successfully design a network cable layout,
you need a thorough knowledge of cable types, their
specifications, and network topologies. This information
helps you assess the organization’s current needs and
plan for future growth
All cabling media have five basic characteristics you must
consider when selecting cable for your
telecommunications systems: throughput and bandwidth,
cost, size and scalability, connectors, and noise immunity
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Chapter Summary
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The three basic types of cable are coaxial, twisted-pair,
and fiber-optic. Coax has a high resistance to
interference, can carry signals farther than twisted-pair
cable before requiring repeaters, and must be terminated
with 50-ohm resistors. Twisted-pair cable is the same as
the cable used to wire telephones, and is the most
common LAN cabling used today. Twisted-pair is
inexpensive, flexible and easy to install. It is shielded,
unshielded, or screened. Fiber is a more expensive
media, but has the highest throughput and bandwidth,
transmits optical signals in the form of light over glass
fibers
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Chapter Summary
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There are two categories of fiber: multi-mode and singlemode. Single-mode fiber transmits in a single mode of
light, which allows data to travel more rapidly and for
greater distances. Multimode fiber transmits up to
hundreds of thousands of modes of light simultaneously,
which allows more data to be transmitted at one time.
However, data cannot travel as fast or as far on multimode
fiber
The coaxial cables used for networks are ThickNet
(10Base5) and ThinNet (10Base2). Both were used
extensively in the early years of Ethernet
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Chapter Summary
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Wireless networking refers to computers that
communicate using standard network rules or protocols,
but without the use of cabling to connect the computers. A
wireless network can be installed as the sole network in
an organization, or it can extend a wired network to areas
where wiring would be too difficult or expensive to
implement. Wireless networks can be configured to
provide the same network functionality as any wired
network
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Chapter Summary
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Network topologies come in three basic geometric shapes:
bus, ring, and star. A fourth type of topology, referred to as
fault-tolerant mesh, is often required for high-availability
networks. The bus topology is the least expensive and the
most difficult to troubleshoot. The ring topology is difficult
to troubleshoot for the same reasons, but it is not subject
to network collisions because of its communication
method. The star topology is the most commonly used,
and it offers the most advantages. It is more expensive
because it uses more cabling than other topologies, but it
is more reliable because of its wiring. If one station goes
down in a star topology, the rest of the network is not
affected
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Chapter Summary
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Before you begin designing a network, you must know its
relative scale and what your customer expects the
network to accomplish. The prerequisites of a network
design include assessing functional requirements, sizing
the network, and defining connectivity needs. Once you
complete the preliminary assessment, you can begin
design work
Before you begin your documentation project or define
your documentation policies, you must first decide what
you need to document. Every network has its own
documentation needs
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