CompTIA Network+ Certification Study Guide part 10 pot

■ ■ RJ Connectors RJ connectors are used with twisted-pair cabling and can be used to provide connectivity to a cable used by telephone and data devices.. Although the connector can be u

provides such a connection between a cable and a device Because the media used on a network can differ, a number of different connectors have been developed over the years

Twisted-pair and Coaxial Cable Connectors

Several types of connectors are available for coaxial cable Depending on the need, connectors that connect to different cable and devices are available for twisted-pair and coaxial These include:

D connectors

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RJ connectors

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DIX connectors

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BNC connectors

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F-Type connectors

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D Connectors

The D connector gets its name from its shape As shown in Figure 2.2, with some imagination, the D connector can be seen as looking like a letter D turned on its side A male connector is one that has pins protruding from it, while a female connector has holes into which the pins fit The number of pins used in a D connector varies, but always correspond to the number used

in the D connector’s name These include:

DB9, which has nine pins

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DB15, which has 15 pins, and we’ll discuss further in this chapter

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when we examine DIX connectors

DB25, which has 25 pins

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RJ Connectors

RJ connectors are used with twisted-pair cabling and can be used to provide connectivity to a cable used by telephone and data devices Because they are used for different purposes, there are several different variations of RJ con-nectors available

rJ-11

RJ-11 connectors are used on twisted- pair cables that are used by tele-phones You can easily find an RJ-11 connector in your home by looking

at the ends of the cable running from

FIGurE 2.2 DB15 Connector.

Connectors 77

your phone into the wall jack They are also used to plug dial-up modems

into the phone line so that computers can dial into the Internet or access

networks remotely using the phone line They are primarily used in North

America and are not widely used in other countries throughout the world

RJ-11 connectors have four pins to support four of the wires in a

twisted-pair cable Although the connector can be used with different categories of

twisted-pair, only two pairs of wires are used, even if the cable contains more

than four wires

rJ-45

The RJ-45 connector is used with twisted-pair cables that support data

com-munication As such, they can be used with Categories 3 and higher of UTP

or STP cabling They are commonly seen on today’s networks, as they are

used on both Ethernet and Token Ring networks

An RJ-45 connector looks like a RJ-11 connector, but wider RJ-45

con-nectors are similar to the phone concon-nectors except that instead of four wires

found in the home system, the network RJ-45 contains eight contacts There

are eight pins in the connector; hence eight wires in the cable are connected

to it Ethernet can use four of the wires or possibly all eight, depending on the

media standard being used As we saw earlier in this chapter, a special

crimp-ing tool is needed to make contact between the pins and the cable inside

rJ-48 and rJ-25

In addition to the RJ-11 and RJ-45 connectors that are used for voice and

data communication, there are also a number of other RJ connectors that

may be found in offices The different types are used to provide different

services, but are all used with twisted-pair cabling

RJ-48 connectors are essentially the same as the RJ-45 connector, but

used with STP cable Like the RJ-45 connector, it uses eight pins to provide

contact with the eight wires in a twisted-pair cable, although a different pin

arrangement is used in connecting the wires

Another example of a RJ is the RJ-25 connector RJ-25 connectors use

six conductors to allow multiple phone lines to be used They are often seen

when telephones have three line connections

DIX

Earlier in this chapter we discussed D connectors and how they consist of

pins that are inserted into a female connector One type of D connector is

a DIX, which is used with an AUI that’s used with 10Base5 cable A DIX

connector looks similar to the connector used for attaching a joystick to a

joystick port DIX connectors can be found on the back of some network

cards and allow the card to be used with different types of media

The meaning of the acronym BNC is something that is a topic of debate It is commonly referred to as a British Naval Connector, but it is also referenced as meaning Bayonet Neill Concelman or Bayonet Nut Connector Regardless of your preference, the BNC connector is used with coaxial cable

If you’ve ever looked at the end of the cable used for your cable televi-sion, you’ve seen one that looks similar to what’s illustrated in Figure 2.3 The copper wire running down the center of the cable protrudes from the center of a BNC barrel connector The connector is threaded, allowing it to

be screwed onto devices with a corresponding connector, so that the wire can fit into the female connection

There are different variations of the BNC connector that can be used on

a network BNC connectors are used to connect 10Base2 coaxial cable to

a hub, while a T-connector (Figure 2.4) can connect a workstation’s cable segment to the network backbone A special crimping tool is used to put the connector on the end of the wire The actual wire runs down the middle and must make contact with the end of the connector shown in the middle

ExErcisE 2.2 Terminating a coaxial cable

Now that you have learned about coaxial cable and how to identify it, we will learn how to terminate a coaxial connector on to a RG type cable

As with twisted-pair cable termination, you will need to use crimping

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and stripping tools when terminating a coaxial cable, although the process itself is a little different For one, you will need a stronger cutter that is sized properly for the job of cutting thick coaxial cable

FIGurE 2.3 BNC Barrel Connector. FIGurE 2.4 BNC T-Connector.

Connectors 79

To terminate the cable, you will need a ratchet crimper, a pair of

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coaxial cable strippers, the coaxial cable itself, and BNC connectors

Use the cable cutter to cut a length of coaxial cable from a bulk spool

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if you have one available The cable should be the proper length for

the job, plus some extra slack for you to make some mistakes when

cutting your cable Remember, never cut cable (especially preexisting

runs) without giving yourself a little extra cable to play with

Next, use the cable stripper to remove the excess jacketing and

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outside coating of the cable

Apply the RG-type connector on the cable and crimp it down

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Do both sides of the cable if not already done

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Make sure you test the cable and ensure that it is within specifications

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RG and F-Type Connectors

F-type connectors are used to terminate coaxial cable and are commonly

seen on RG-58 (Thinnet) and RG-59 (Thicknet) coaxial Although it is an

older type of connector, it is still frequently used These connectors have the

ability to screw onto televisions, VCRs, and devices for cable television, and

are low in cost

Fiber Connectors

There are a number of different connectors that are used with fiber-optic

cable As is the case with some of the connectors available for twisted-pair

and coaxial cable, some of these are used with older technology and are not

routinely seen on modern networks They include:

Straight tip

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Standard connector

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Local connector

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Mechanical transfer registered jack

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Standard Connectors

SC stands for standard connector, and is a suitable name, as it’s the most

com-mon type of connector used with fiber-optic cable It is often used with Cisco

equipment As shown in Figure 2.5, the SC terminates the fiber-optic cable by

attaching to its end, using a locking mechanism that clicks into place

ST Connectors

ST connectors are an older version of connector used on fiber-optic cable It

is often seen on older 10BaseFL networks The ST connector has a screw-on type of locking mechanism that attaches to the tip of a fiber-optic cable and terminates it In using this type of connector (shown in Figure 2.6), you will find that it has the look and feel of a BNC connector, making it easy to use

Local Connectors

The LC is another common connector used on fiber-optic networks LC is a high-performance connector that is used on many networks LC connectors use a locking mechanism that’s similar to the SC, which click into place The connector is seated into place by pushing it in and snapping it into place

FIGurE 2.5 SC Connector. FIGurE 2.6 ST Connector.

Exam warning

An easy way to remember the SC is by thinking of its name (standard connector), which indicates that it’s the most common one used today An alternative method of

remember-ing it is to think of SC as stick and click This will help you to remember that it uses a

click-into-place locking mechanism.

Exam warning

An easy way to remember the characteristics of an ST connector is by using its nickname

stick and twist This will help you to remember that it is a screw-on type of connector, as

you stick and twist it on.

Exam warning

An easy way to remember the characteristics of an LC connector is by thinking of the

term lock and click This will help you to remember that its locking mechanism requires

you to push and click it into place.

Recognizing Category 3, 5, 5e, and 6 UTP

Mechanical Transfer Registered

Jacks

The MTRJ is similar to the LC

nector in that it is a duplex

con-nector As shown in Figure 2.7, it

uses a form factor and latch that is

similar to the RJ-45 connectors

dis-cussed earlier in this chapter It is

also easier to terminate and install

than some of the other types of fiber-optic connectors we’ve discussed,

such as the ST and SC connectors

rECoGNIzING CATEGory 3, 5, 5E, ANd 6 uTp, STp,

CoAxIAl CABlE, SMF opTICS CABlE, MMF opTIC

CABlE, ANd opTIC CABlE

Although we’ve already provided you with a lot of information about

cabling and their respective issues, it’s time to go in depth into the types

of cabling you’ll find on networks and the Network exam As we’ve

discussed, there are three types of physical media that can be used on

a network: coaxial cable, twisted-pair cable, and fiber-optic cable These

different media types can be further broken down into different categories

and types of cabling, which are either used for specific purposes or provide

greater bandwidth

Category 3, 5, 5e, and 6 uTp

UTP cabling is the most common type of physical media on networks today

The typical twisted-pair cable for network use contains three or four pairs

of wires As shown in Figure 2.8, each pair of wires contained in the cable

is twisted around each other, which helps shield against crosstalk and other

forms of EMI Although the twisted wires do provide a certain amount of

immunity from the infiltration of unwanted interference, this doesn’t mean

that UTP is the best solution against EMI Twisted-pair cable is susceptible

to interference and should not be used in environments containing large

electrical or electronic devices

Because UTP is used for everything from telephone cable to

high-speed network cable, the Electrical Industry Association established

different categories of UTP These categories are rated by a number of

factors, including the electrical characteristics, conductor size, and twists

FIGurE 2.7 MTRJ Connector.

per foot Because new categories are also an indication of enhancements

in the wiring, the higher categories are also new evolutions of twisted-pair The various categories, which

are simply referred to as CAT, are

shown in Table 2.6

Table 2.6 Categories of Twisted-Pair Cabling

CAT 1 Up to 1 Mbps Voice communication in older analog telephone systems

and also used as doorbell wiring This type of cabling is not suitable for data transmissions.

CAT 2 4 Mbps Low performance cable; used for voice and low-speed data

transmission.

CAT 3 16 Mbps Voice communication in newer telephone systems Rated at

10 MHz, this is the minimum category of UTP that can be used for data transmissions on networks; can be used for Ethernet, Fast Ethernet, and Token Ring.

CAT 4 20 Mbps Used for data and voice transmission; rated at 20 MHz; can be

used for Ethernet, Fast Ethernet, and Token Ring.

CAT 5 100 Mbps (4 pairs) Typically used for Ethernet networks running at 10 or

100 Mbps Used for data and voice transmission; rated at 100 MHz; suitable for Ethernet, Fast Ethernet, Gigabit Ethernet, Token Ring, and 155 Mbps ATM.

CAT 5e 1000 Mbps Recommended for all new installations and was designed

for transmission speeds of up to 1 Gbps (Gigabit Ethernet) Similar to Category 5, but manufacturing process is refined; higher grade cable than Category 5; rated at 200 MHz; suitable for Ethernet, Fast Ethernet, Gigabit Ethernet, Token Ring, and 155 Mbps ATM.

CAT 6 Same as CAT5e, but higher standard Rated at 250 MHz; suitable for

Ethernet, Fast Ethernet, Gigabit Ethernet, Token Ring, and 155 Mbps ATM CAT 6e Support for 10 Gigabit Ethernet Similar to Category 6, but is a proposed

international standard to be included in ISO/IEC 11801.

CAT 7 Not official standard at time of this writing Still in development Rated at

600 MHz; suitable for Ethernet, Fast Ethernet, Gigabit Ethernet, Token Ring, and 155 Mbps ATM.

FIGurE 2.8 Unshielded Twisted-Pair.

Test day Tip

Although there are a number of different categories of UTP, the Network exam expects you to know the details of CAT 3, 5, 5e, and 6 cables You should only review the other categories to know what is being offered as incorrect choices.

Recognizing Category 3, 5, 5e, and 6 UTP

Category 3 is the minimum grade of cable that supports networking,

but it is not the best choice for networks CAT3 is a voice-grade cable used

in phone networks, and its only real benefit beyond being able to

sup-port data communication is that it already exists in most office buildings

and homes Regardless of this, CAT 5 or higher should be used in new

networks

Most of the UTP cable that’s found in networks today is Category 5 CAT

5 is a multipair performance cable with eight wires (four pairs) that supports

higher bandwidth and is typically used for Ethernet networks that run at

10 or 100 Mbps Until recent enhancements were made to UTP, this grade

of cabling was the standard for new network installations

Category 5e is essentially the same as CAT 5 cable, but adheres to more

stringent standards that make it as a better candidate for new installations

that will use Gigabit Ethernet It is designed for transmission speeds of up to

1 Gbps and has been made an official standard

Category 6 is another enhancement to the previous grades and provides

support for 10 Gigabit Ethernet It is officially a part of the 568A standard,

making it a standard grade of cable for UTP installations

STp

As its name says, the difference between the unshielded and shielded

variet-ies of twisted-pair is the shield As shown in Figure 2.9, STP has a shield

that’s usually made of aluminum/polyester that resides between the outer

jacket and the wires The shield is designed to keep more interference out,

protecting the wires inside from EMI caused by outside sources STP also

uses a much higher quality protective jacket for greater insulation

Coaxial Cable

Coaxial (or coax) cable looks like

the cable used to bring the cable

TV signal to our television As

shown in Figure 2.10, one strand

(a solid-core wire) runs down the

middle of the cable Around that

Exam warning

Category 1 and 2 of UTP is for voice communications Category 3 or higher can be used

for data communications, but Category 5 or higher should be used On the exam, you

may see these categories abbreviated, so that they use the term CAT for category Don’t

let this confuse you.

Plastic Covering Shielding Copper

Wire Insulation

FIGurE 2.9 Shielded Twisted-Pair.

strand is insulation Covering that insulation is braided wire and metal foil, which shields against EMI A final layer of insulation covers the braided wire Coaxial cable is resistant to the interference and signal weakening that other cabling, such as UTP cable, can experience In general, coax is bet-ter than UTP cable at connecting longer distances and for reliably supporting higher data rates with less sophisticated equipment

Just because the TV cable is coax does not mean it will work with com-puter networks Network coaxial cable has very specific requirements, such

as the gauge, the impedance, and the attenuation

Thinnet refers to RG-58 cabling, which is a flexible coaxial cable about 1/4 inch thick Thinnet is used for short-distance communication and is flexible enough to facilitate routing between workstations Thinnet connects directly to a workstation’s network adapter card using a BNC T-connector and uses the network adapter card’s internal transceiver 10Base2 refers to Ethernet LANs that use Thinnet cabling

Thicknet coaxial cable can support data transfer over longer distances better than Thinnet can and is usually used as a backbone to connect several smaller Thinnet-based networks The diameter of a Thicknet cable is about 1/2 inch and is harder to work with than a Thinnet cable

A transceiver is connected directly to Thicknet cable using a connector known as a piercing tap Connection from the transceiver to the network adapter card is made using a drop cable to connect to the adapter unit interface port connector 10Base5 refers to Ethernet LANs that use Thick-net cabling

SMF-optic Cable

Optical fibers carry digital data signals in the form of modulated pulses of light As shown in Figure 2.11, an optical fiber consists of an extremely

thin cylinder of glass or optical fiber, called the core, surrounded by a concentric layer of glass, known as the cladding A cable may contain

FIGurE 2.10 Coaxial Cable.

Exam warning

Although coax is not as commonly used as it used to be, the Network exam expects you

to understand what it is and how it works You will need to understand the lengths of cabling that can be used with Thinnet and Thicknet coax as well as the transmission speeds.

Other Media 85

two fibers per cable – one to

trans-mit and one to receive – or a single

fiber However, often, multiple fibers

are bundled into the center of the

cable The fiber and cladding can

be surrounded by a liquid gel that

reflects signals back into the fiber to

reduce signal lost, or a plastic spacer

surrounded by Kevlar fiber Each of

these components making up the

fiber-optic cable is further protected

by a plastic covering that encases

everything within the cable

There are two different types of

fiber-optic cabling that may be used

to carry data: SMF and MMF SMF is

optical fiber that’s designed to

trans-mit a single beam of light from a laser

The beam of modulated light provides

greater bandwidth and allows cable to

be run over longer distances Because

of these features, SMF is used for long

distance transmissions such as in

tele-phone and cable television networks

MMF-optic Cable

MMF is used to carry multiple beams of light at the same time, using

a light emitting diode (LED) as a light source Each of the beams is at a

slightly different reflection angle within the core of the fiber Because the

light tends to disperse over distance, MMF is used for connecting locations

within relatively short distances

oThEr MEdIA

Although the cabling, connectors, and other elements of a network we’ve

discussed in this chapter are either traditional components of a network, or

have grown to become standard, there are other technologies that are either

new, not readily associated with networking, or often forgotten Nevertheless,

elements such as wireless technologies, FireWire, and transceivers are

impor-tant to networking Such media is not only covered on the Network exam,

but it is important to the design or development of your network

FIGurE 2.11 Fiber-Optic Cabling.