3.1
Chapter 3: Network Media and
Topologies
Plenum vs. non-plenum
Media converters:
Distance limitations and speed limitations
Broadband over powerline
3.2 Categorize standard connector types based on
network media.
Copper:
3.3 Compare and contrast different wireless
standards.
3.4 Categorize WAN technology types and
properties.
Properties:
3.5 Describe different network topologies.
3.6 Given a scenario, troubleshoot common
physical connectivity problems.
3.7 Compare and contrast different LAN
technologies.
Properties:
3.8 Identify components of wiring
distribution.
Although the basic concept of connecting computers hasn't
changed very much since the mid-1980s, the methods used to connect them have
changed dramatically. The technologies that are in use now have evolved over the
past 30 years to the point where they are today. These technologies will
continue to evolve. The components we use in our networks have also evolved
because of these technologies.
When you connect computers, your main goal is to provide fast
communication with as few errors as possible. You should understand that the
type of media and topology you use in your network will largely determine your
ability to reach this goal. In addition, you should know that the components you
choose for a network will also determine your capability to control network
traffic. In this chapter, I will discuss several networking media and topologies
and compare the features that they, and the components that use them, bring to
your network design to help you control traffic within your network.
As networking has evolved, the types of cable and their
properties have dramatically changed. We have moved from using cables made only
from copper wire to also using cables made from glass fibers. Each of these
general categories of cable has its own properties and has many options from
which to select. In this section, I will discuss the most common types of cable
and their corresponding properties.
Fiber-optic cable (fiber) is often used in network backbones to
provide high bandwidth for fast, reliable communications. There are two main
types of fiber-optic cable: singlemode and multimode. In this section, I will
discuss the properties, advantages, and disadvantages of each type.
Multimode fiber-optic cable (MMF) uses
light to communicate a signal and disperses it into numerous paths (which is why
it's multi) as it travels through the core and is
reflected back via cladding, a special material that lines
the core and focuses the light back onto it. Multimode fiber provides high
bandwidth at high speeds over medium distances (up to about 3,000 feet) but can
be inconsistent for very long runs. Because of this, multimode fiber is
generally used within a smaller area of a building. Multimode fiber is available
in glass or in a plastic version that makes installation easier and increases
installation flexibility. As with singlemode fiber, multimode fiber can be used
when electrical interference is present, since it is completely immune to it.
Figure 3.1 shows the how light is split into multiple paths in a
multimode fiber-optic cable.
Singlemode fiber-optic cable (SMF) is a
high-speed, high-distance media. It consists of a single strand, or sometimes
two strands, of glass fiber that carries the signals. The light source that is
generally used with singlemode fiber is a laser, although light-emitting diodes
(LEDs) may also be used. With singlemode fiber, a single light source is
transmitted from end to end and pulsed to create communication. Singlemode fiber
is used for long runs because it can transmit data 50 times farther than
multimode fiber and at a faster rate. For example, singlemode fiber might be
used on an organization's corporate campus between buildings. Since the
transmission media is glass, installing singlemode fiber can be a bit tricky.
Other layers are protecting the glass core, but the cable still should not be
crimped or pinched around any tight corners. It is, however, completely immune
to electrical interference since light is used instead of electrical signals.
Figure 3.2 illustrates the layers included in singlemode
fiber-optic cable.
Fiber-optic cable is becoming more prevalent, but copper cables
are by far the most used in networks today. There are many forms of copper cable
and many technologies that have evolved around them.
Unshielded twisted-pair (UTP) cable is
the most common type of cable in use today. UTP is used most often because it is
far easier to install than STP (which I will discuss next). It is commonly used
in the access and distribution areas of a network. The only protection from
electrical interference provided by UTP is that the pairs of wires within the
cable are twisted, which is usually enough. Figure 3.3 shows a UTP cable.
Shielded twisted-pair (STP) resembles UTP
except that it includes a foil shield that covers the wires and adds another
layer of protection against outside magnetic interference. For this protection
to be effective, the connections have to be properly grounded. This adds to the
complexity of installations, so most organizations have opted to use fiber-optic
cable instead of STP when electromagnetic interference is a problem. Figure 3.4 shows an STP cable.
The category of a twisted-pair cable indicates the tightness of
the twist applied to the wire pairs in the cable. The twist in wire pairs
prevents an electrical interference called crosstalk from
affecting the communication. Crosstalk occurs when a signal bleeds over from one
wire to another (even through the insulation of the wire). The tighter the
twist, the faster you can transmit information through a cable without suffering
from crosstalk. Table 3.1 shows the maximum speed of the main cable categories.
Category 5e (enhanced) is the cable type that is currently recommended as a
minimum for all new installations.
Coaxial cable consists of an inner core wire and an outer braid
of insulating wire. The inner core wire carries the entire signal. Figure 3.5 shows a coaxial cable. In the late 1980s, coaxial cable was used as the backbone of network segments
and to connect computers to the bus topology that made up the network. The
larger coaxial cables that generally made up the backbone were referred to as thicknet, while the smaller “drop cables” used to connect the
computers were called thinnet. Sometimes we used a special
device called a vampire tap to pierce the coaxial cable
and get the signal from the core. Oh, those were the days!
Coaxial cable is rarely used anymore for network backbones or
to connect computers, but it is being used today for television connections and
to connect cable modems to broadband Internet connections. I will focus our
attention on the coaxial cable used for computers today, for which there are
basically two standards in general use today: RG-59 and RG-6. Of these, RG-6
offers a thicker core wire for less resistance and better performance.
Let's say you wanted to attach a switch to a switch. By this
definition, the devices are similar, and therefore you should use a crossover
cable instead of a straight-through cable. Suppose you accidentally used a
straight-through cable where you should have used a crossover cable; would that
work? Well, yes--most modern switches would autosense the difference and “switch
the pins” for you. However, for the exam, you should know that straight-through cables are used
to connect dissimilar network devices, and crossover cables are used to connect
similar devices. Table 3.2 illustrates the most common matchups and which cable
to use.
A channel service unit/data service unit (CSU/DSU) is a digital
interface device used to connect a router to a digital circuit, such as a T1 or
T3 line. (I will discuss the CSU/DSU in greater detail later in this chapter.)
If you should need to connect one CSU/DSU to another, you would usde a specially
pinned cable, referred to as a T1 crossover cable. It is
pinned in such a way as to let the send circuits on the router connect to the
receive circuits on the CSU/DSU, and vice versa.
A straight (or straight-through) cable is
the most common type of cable used in a network. It is typically referred to as
a patch cable, because it is used to patch one network
device to another. Straight-through cables are generally used to connect network
devices that are dissimilar.
For example, in a typical network, a computer is attached to a
wall jack using a straight-through cable. The wall jack is attached to a patch
panel (for flexibility and redundancy), and then the patch panel is attached to
a switch. In essence, a computer attached to a switch uses a straight-through
cable. A computer and a switch are very different in regard to how they function
on a network and therefore are considered dissimilar.
The difference between plenum and non-plenum cable involves how
each is constructed and where it is authorized for use. Many large multistory
buildings are designed to circulate air through the spaces between the ceiling
of one story and the floor of the next. As I mentioned in a previous chapter,
this area in between floors is referred to as the plenum.
It is an area that is generally perfect for running cables to connect the many
computers in the building.
However, in the event of a fire, the cables in the plenum can
become a serious hazard in two ways. First, their insulation can give off a
poisonous smoke that would then be circulated throughout the building. Second, they can become a
“wick” for the fire and actually help spread it from room to room and floor to
floor. Not pretty, huh?
To prevent both of these occurrences, the National Fire
Protection Association (NFPA) regulates the use of cables in the plenum to those
that it has tested to be safe. A plenum cable is therefore tested to be fire
retardant and to create no (or a very small amount of) smoke and poisoned gas
when burned. A non-plenum cable does not meet these standards and can therefore
be used anywhere except in a plenum. Non-plenum cables are typically less
expensive than plenum cables. However, most organizations use plenum cable only
in the plenum for obvious reasons.
As networking has evolved, the types of cable and their
properties have dramatically changed. We have moved from using cables made from
copper wire to using cables made from glass fibers. Each of these general
categories of cable has its own properties and has many options from which to
select. Perhaps one of the best decisions you could make in your network would
be to use a combination of these types of cables and technologies. If you do
that, then you will need to have media converters at the points where one type
of cable and technology connects to another. In this section, I will discuss the
most common types of media converters and where you would use each one.
Since you would most likely use singlemode fiber between
buildings on a campus, this type of media converter would be used in each
building as the fiber-based data signal in the form of light comes into the
building to be carried farther through the building in the form of electricity.
See Figure 3.6.
In some organizations, multimode fiber is used as the backbone
within a building. This allows the backbone to carry more data at faster speeds
than would be possible using only copper cable. Even when multimode fiber is
used in this way, it is unlikely that it will be used all the way to the
computers. Typically a multimode fiber to Ethernet converter will be used
between the backbone segment and the patch panels that will lead to the wall
jacks and finally to the computers themselves.
In the past, coaxial cable was used as a backbone in some
buildings. This is not done very often anymore, but coaxial cables are sometimes
used to connect cable modems for the purposes of Internet communications or
telecommunications. If you wanted to bring in high-bandwidth communications from
a cable provider and then distribute them throughout your network backbone, you
would use a fiber-to-coaxial converter (see Figure 3.7).
As I mentioned earlier, singlemode fiber is typically used
between buildings because it can span greater distances, whereas multimode fiber
is used within each building because it can have many channels of communication.
Therefore, if you use both, the connections between your buildings will use a
singlemode to multimode converter. The singlemode fiber will bring in pulses of
light in one stream, and the multimode fiber will then divide the signals into
multiple channels.
As you might imagine, the capability of each of these
technologies varies greatly from one to the next. For this reason, you will need
to choose carefully when you are considering using one technology over another.
Two of most important aspects of each type of cable are its maximum speed and
maximum distance. Later in this chapter, I will discuss the various LAN and WAN
technologies including the maximum distance for each technology.
Broadband over powerline (BPL) is a
system that carries data on a conductor wire that is also used for electrical
power transmission. In the past, power lines were considered as a suitable media
for high-bandwidth communications. Recent advances in technology are now making
high-bandwidth communications possible and opening the door for computer
communications in SOHO and enterprise networks. You can use a BPL converter to
facilitate communications over power lines where other types of communication
lines would be difficult or impossible to install.
Know the types of fiber-optic cable There
are two main types of fiber-optic cable: multimode fiber and singlemode fiber.
Multimode fiber is typically used within buildings and can disperse the light
into multiple paths. Singlemode fiber is typically used between buildings and
consists of a single light source that is pulsed.
Know the types of copper cables There are
three main types of copper cables that are used in today's networks: UTP, STP,
and coaxial. UTP cable is the most common type of cable by far. Since they do
not have any shielding, they are very easy to install; however, they are not
suitable for installations that are close to large magnets, motors, speakers,
and the like. STP cables are less commonly used because they are much more
difficult to install. They provide a layer of shielding that must be grounded to
be effective. They are not used much in today's networks because fiber-optic
cables provide a complete immunity to electrical interference. Coaxial cables
are still used in today's networks, but in a very different way than they were
in the past. They consist of one core wire that carries all of the signal and a
braided mesh that acts as a shield. They are primarily used to connect cable
modems to the connections from a cable Internet provider.
Know the categories of UTP cables and their
purpose There any many categories of cables ranging from Category 3 to
Category 6a. Generally speaking, the higher the category number, the faster you
can push data through it without problems caused by signal bleed called crosstalk. You should always use the appropriate category for
the task at hand.
Understand the main types of cables and their
uses Straight, or straight-through, cables are used
to patch network components together that are not similar to each other such as
when connecting a computer to a switch. They are also referred to as patch cables. Crossover cables are used to connected similar
devices together such as a switch to a switch, router to a router, or even a PC
to a router (a PC can perform a routing function so it is similar to a router).
A T1 crossover cable is a specialized crossover that is used to connect a
CSU/DSU to another CSU/DSU.
Understand the difference between plenum and
non-plenum cable A plenum is the space in a building that is between the
ceiling of one floor and the floor of the next. Since air is generally
circulated in this area, the NFPA regulates that only specialized cables can be
used that have insulation that doesn't wick fire or give off poisonous gases
when it burns. These specialized cables are referred to as plenum cables. In all other areas of the network, non-plenum
cables can be used.
Understand media converters Since we use
fiber-optic, copper UTP/STP, and even coaxial cables in the same network, we
often need converters. There are many types of converters, and each has a use in
the network. Review the
definitions of the different media types and their uses, and the place that the
converter will be used in the network will be evident for each.
Understand Broadband over powerline
Broadband over powerline carries data on a conductor wire that is also carrying
electrical power transmission. This can facilitate options in SOHO network and
even larger enterprise-type networks. You can use this technology in areas where
other media would be difficult or even impossible to install.
CompTIA Network+ exam objectives covered in this chapter:
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Although the basic concept of connecting computers hasn't
changed very much since the mid-1980s, the methods used to connect them have
changed dramatically. The technologies that are in use now have evolved over the
past 30 years to the point where they are today. These technologies will
continue to evolve. The components we use in our networks have also evolved
because of these technologies.When you connect computers, your main goal is to provide fast
communication with as few errors as possible. You should understand that the
type of media and topology you use in your network will largely determine your
ability to reach this goal. In addition, you should know that the components you
choose for a network will also determine your capability to control network
traffic. In this chapter, I will discuss several networking media and topologies
and compare the features that they, and the components that use them, bring to
your network design to help you control traffic within your network.| Note |
For more detailed information on Domain 3's topics, please see
CompTIA
Network+ Study Guide,
2nd Edition
(9781118137550) or CompTIA Network+ Deluxe Study Guide, 2nd Ed (9781118137543),
both published by Sybex. |
3.1
Categorize standard media types and associated properties
As networking has evolved, the types of cable and their
properties have dramatically changed. We have moved from using cables made only
from copper wire to also using cables made from glass fibers. Each of these
general categories of cable has its own properties and has many options from
which to select. In this section, I will discuss the most common types of cable
and their corresponding properties.
Fiber
Fiber-optic cable (fiber) is often used in network backbones to
provide high bandwidth for fast, reliable communications. There are two main
types of fiber-optic cable: singlemode and multimode. In this section, I will
discuss the properties, advantages, and disadvantages of each type.Multimode
Multimode fiber-optic cable (MMF) uses
light to communicate a signal and disperses it into numerous paths (which is why
it's multi) as it travels through the core and is
reflected back via cladding, a special material that lines
the core and focuses the light back onto it. Multimode fiber provides high
bandwidth at high speeds over medium distances (up to about 3,000 feet) but can
be inconsistent for very long runs. Because of this, multimode fiber is
generally used within a smaller area of a building. Multimode fiber is available
in glass or in a plastic version that makes installation easier and increases
installation flexibility. As with singlemode fiber, multimode fiber can be used
when electrical interference is present, since it is completely immune to it.
Figure 3.1 shows the how light is split into multiple paths in a
multimode fiber-optic cable. "Click To expand")
Singlemode
Singlemode fiber-optic cable (SMF) is a
high-speed, high-distance media. It consists of a single strand, or sometimes
two strands, of glass fiber that carries the signals. The light source that is
generally used with singlemode fiber is a laser, although light-emitting diodes
(LEDs) may also be used. With singlemode fiber, a single light source is
transmitted from end to end and pulsed to create communication. Singlemode fiber
is used for long runs because it can transmit data 50 times farther than
multimode fiber and at a faster rate. For example, singlemode fiber might be
used on an organization's corporate campus between buildings. Since the
transmission media is glass, installing singlemode fiber can be a bit tricky.
Other layers are protecting the glass core, but the cable still should not be
crimped or pinched around any tight corners. It is, however, completely immune
to electrical interference since light is used instead of electrical signals.
Figure 3.2 illustrates the layers included in singlemode
fiber-optic cable. "Click To expand")
Copper
Fiber-optic cable is becoming more prevalent, but copper cables
are by far the most used in networks today. There are many forms of copper cable
and many technologies that have evolved around them.UTP
Unshielded twisted-pair (UTP) cable is
the most common type of cable in use today. UTP is used most often because it is
far easier to install than STP (which I will discuss next). It is commonly used
in the access and distribution areas of a network. The only protection from
electrical interference provided by UTP is that the pairs of wires within the
cable are twisted, which is usually enough. Figure 3.3 shows a UTP cable. "Click To expand")
STP
Shielded twisted-pair (STP) resembles UTP
except that it includes a foil shield that covers the wires and adds another
layer of protection against outside magnetic interference. For this protection
to be effective, the connections have to be properly grounded. This adds to the
complexity of installations, so most organizations have opted to use fiber-optic
cable instead of STP when electromagnetic interference is a problem. Figure 3.4 shows an STP cable.
CAT3, 5, 5e, 6, and 6a
The category of a twisted-pair cable indicates the tightness of
the twist applied to the wire pairs in the cable. The twist in wire pairs
prevents an electrical interference called crosstalk from
affecting the communication. Crosstalk occurs when a signal bleeds over from one
wire to another (even through the insulation of the wire). The tighter the
twist, the faster you can transmit information through a cable without suffering
from crosstalk. Table 3.1 shows the maximum speed of the main cable categories.
Category 5e (enhanced) is the cable type that is currently recommended as a
minimum for all new installations.|
Category 3 |
Category 5 |
Category 5e |
Category 6 |
Category 6a | |
|---|---|---|---|---|---|
|
Maximum Speed |
10Mbps |
100Mbps |
1000Mbps |
1000Mbps |
1000Mbps |
Open table as spreadsheet| Note |
You may have noticed that categories 5e, 6, and 6a all have the
same maximum speed, so why would you choose one over another? For one thing,
compared with category 5e, categories 6 and 6a have more stringent
specifications regarding crosstalk and noise. They also require a slightly
modified RJ-45 connector to meet the specification and hold the tighter
twist. |
Coaxial
Coaxial cable consists of an inner core wire and an outer braid
of insulating wire. The inner core wire carries the entire signal. Figure 3.5 shows a coaxial cable. In the late 1980s, coaxial cable was used as the backbone of network segments
and to connect computers to the bus topology that made up the network. The
larger coaxial cables that generally made up the backbone were referred to as thicknet, while the smaller “drop cables” used to connect the
computers were called thinnet. Sometimes we used a special
device called a vampire tap to pierce the coaxial cable
and get the signal from the core. Oh, those were the days! "Click To expand")
Coaxial cable is rarely used anymore for network backbones or
to connect computers, but it is being used today for television connections and
to connect cable modems to broadband Internet connections. I will focus our
attention on the coaxial cable used for computers today, for which there are
basically two standards in general use today: RG-59 and RG-6. Of these, RG-6
offers a thicker core wire for less resistance and better performance.Crossover
Let's say you wanted to attach a switch to a switch. By this
definition, the devices are similar, and therefore you should use a crossover
cable instead of a straight-through cable. Suppose you accidentally used a
straight-through cable where you should have used a crossover cable; would that
work? Well, yes--most modern switches would autosense the difference and “switch
the pins” for you. However, for the exam, you should know that straight-through cables are used
to connect dissimilar network devices, and crossover cables are used to connect
similar devices. Table 3.2 illustrates the most common matchups and which cable
to use.|
Device 1 |
Device 2 |
Cable type |
|---|---|---|
|
PC |
Switch |
Straight |
|
PC |
PC |
Crossover |
|
Switch |
Router |
Straight |
|
Router |
Router |
Crossover |
|
PC |
Router |
Crossover |
| Note |
Most of the entries in Table 3.2 are very straightforward; however, the last one is a
bit tricky. The reason that a connection between a PC and a router uses a
crossover cable is that a PC is very much like a router. In fact, you can create
a router from a PC with an additional NIC and the right
configuration. |
T1 Crossover
A channel service unit/data service unit (CSU/DSU) is a digital
interface device used to connect a router to a digital circuit, such as a T1 or
T3 line. (I will discuss the CSU/DSU in greater detail later in this chapter.)
If you should need to connect one CSU/DSU to another, you would usde a specially
pinned cable, referred to as a T1 crossover cable. It is
pinned in such a way as to let the send circuits on the router connect to the
receive circuits on the CSU/DSU, and vice versa.Straight-through
A straight (or straight-through) cable is
the most common type of cable used in a network. It is typically referred to as
a patch cable, because it is used to patch one network
device to another. Straight-through cables are generally used to connect network
devices that are dissimilar.For example, in a typical network, a computer is attached to a
wall jack using a straight-through cable. The wall jack is attached to a patch
panel (for flexibility and redundancy), and then the patch panel is attached to
a switch. In essence, a computer attached to a switch uses a straight-through
cable. A computer and a switch are very different in regard to how they function
on a network and therefore are considered dissimilar.| Note |
To assure connectivity throughout your network, the same wiring
standard should be used in the cables, the patch panels, and other network
connections. There are two competing standards, T568a and T568B, which I will
discuss in greater detail later in this
chapter. |
Plenum vs. non-plenum
The difference between plenum and non-plenum cable involves how
each is constructed and where it is authorized for use. Many large multistory
buildings are designed to circulate air through the spaces between the ceiling
of one story and the floor of the next. As I mentioned in a previous chapter,
this area in between floors is referred to as the plenum.
It is an area that is generally perfect for running cables to connect the many
computers in the building.However, in the event of a fire, the cables in the plenum can
become a serious hazard in two ways. First, their insulation can give off a
poisonous smoke that would then be circulated throughout the building. Second, they can become a
“wick” for the fire and actually help spread it from room to room and floor to
floor. Not pretty, huh?To prevent both of these occurrences, the National Fire
Protection Association (NFPA) regulates the use of cables in the plenum to those
that it has tested to be safe. A plenum cable is therefore tested to be fire
retardant and to create no (or a very small amount of) smoke and poisoned gas
when burned. A non-plenum cable does not meet these standards and can therefore
be used anywhere except in a plenum. Non-plenum cables are typically less
expensive than plenum cables. However, most organizations use plenum cable only
in the plenum for obvious reasons.
Media converters
As networking has evolved, the types of cable and their
properties have dramatically changed. We have moved from using cables made from
copper wire to using cables made from glass fibers. Each of these general
categories of cable has its own properties and has many options from which to
select. Perhaps one of the best decisions you could make in your network would
be to use a combination of these types of cables and technologies. If you do
that, then you will need to have media converters at the points where one type
of cable and technology connects to another. In this section, I will discuss the
most common types of media converters and where you would use each one.Singlemode fiber to Ethernet
Since you would most likely use singlemode fiber between
buildings on a campus, this type of media converter would be used in each
building as the fiber-based data signal in the form of light comes into the
building to be carried farther through the building in the form of electricity.
See Figure 3.6.
Multimode fiber to Ethernet
In some organizations, multimode fiber is used as the backbone
within a building. This allows the backbone to carry more data at faster speeds
than would be possible using only copper cable. Even when multimode fiber is
used in this way, it is unlikely that it will be used all the way to the
computers. Typically a multimode fiber to Ethernet converter will be used
between the backbone segment and the patch panels that will lead to the wall
jacks and finally to the computers themselves.Fiber to coaxial
In the past, coaxial cable was used as a backbone in some
buildings. This is not done very often anymore, but coaxial cables are sometimes
used to connect cable modems for the purposes of Internet communications or
telecommunications. If you wanted to bring in high-bandwidth communications from
a cable provider and then distribute them throughout your network backbone, you
would use a fiber-to-coaxial converter (see Figure 3.7).
Singlemode to multimode fiber
As I mentioned earlier, singlemode fiber is typically used
between buildings because it can span greater distances, whereas multimode fiber
is used within each building because it can have many channels of communication.
Therefore, if you use both, the connections between your buildings will use a
singlemode to multimode converter. The singlemode fiber will bring in pulses of
light in one stream, and the multimode fiber will then divide the signals into
multiple channels.
Distance limitations and speed
limitations
As you might imagine, the capability of each of these
technologies varies greatly from one to the next. For this reason, you will need
to choose carefully when you are considering using one technology over another.
Two of most important aspects of each type of cable are its maximum speed and
maximum distance. Later in this chapter, I will discuss the various LAN and WAN
technologies including the maximum distance for each technology.
Broadband over powerline
Broadband over powerline (BPL) is a
system that carries data on a conductor wire that is also used for electrical
power transmission. In the past, power lines were considered as a suitable media
for high-bandwidth communications. Recent advances in technology are now making
high-bandwidth communications possible and opening the door for computer
communications in SOHO and enterprise networks. You can use a BPL converter to
facilitate communications over power lines where other types of communication
lines would be difficult or impossible to install.
Exam Essentials
Know the types of fiber-optic cable There
are two main types of fiber-optic cable: multimode fiber and singlemode fiber.
Multimode fiber is typically used within buildings and can disperse the light
into multiple paths. Singlemode fiber is typically used between buildings and
consists of a single light source that is pulsed.Know the types of copper cables There are
three main types of copper cables that are used in today's networks: UTP, STP,
and coaxial. UTP cable is the most common type of cable by far. Since they do
not have any shielding, they are very easy to install; however, they are not
suitable for installations that are close to large magnets, motors, speakers,
and the like. STP cables are less commonly used because they are much more
difficult to install. They provide a layer of shielding that must be grounded to
be effective. They are not used much in today's networks because fiber-optic
cables provide a complete immunity to electrical interference. Coaxial cables
are still used in today's networks, but in a very different way than they were
in the past. They consist of one core wire that carries all of the signal and a
braided mesh that acts as a shield. They are primarily used to connect cable
modems to the connections from a cable Internet provider.Know the categories of UTP cables and their
purpose There any many categories of cables ranging from Category 3 to
Category 6a. Generally speaking, the higher the category number, the faster you
can push data through it without problems caused by signal bleed called crosstalk. You should always use the appropriate category for
the task at hand.Understand the main types of cables and their
uses Straight, or straight-through, cables are used
to patch network components together that are not similar to each other such as
when connecting a computer to a switch. They are also referred to as patch cables. Crossover cables are used to connected similar
devices together such as a switch to a switch, router to a router, or even a PC
to a router (a PC can perform a routing function so it is similar to a router).
A T1 crossover cable is a specialized crossover that is used to connect a
CSU/DSU to another CSU/DSU.Understand the difference between plenum and
non-plenum cable A plenum is the space in a building that is between the
ceiling of one floor and the floor of the next. Since air is generally
circulated in this area, the NFPA regulates that only specialized cables can be
used that have insulation that doesn't wick fire or give off poisonous gases
when it burns. These specialized cables are referred to as plenum cables. In all other areas of the network, non-plenum
cables can be used.Understand media converters Since we use
fiber-optic, copper UTP/STP, and even coaxial cables in the same network, we
often need converters. There are many types of converters, and each has a use in
the network. Review the
definitions of the different media types and their uses, and the place that the
converter will be used in the network will be evident for each.Understand Broadband over powerline
Broadband over powerline carries data on a conductor wire that is also carrying
electrical power transmission. This can facilitate options in SOHO network and
even larger enterprise-type networks. You can use this technology in areas where
other media would be difficult or even impossible to install.