CIS 1140 Network Fundamentals

Chapter 3 Transmission Basics and Networking Media

Collected and CompiledBy JD WillardMCSE, MCSA, Network+, Microsoft IT Academy AdministratorComputer Information Systems InstructorAlbany Technical College

Attention: Accessing Demos• This course presents many demos. • The Demos require that you be logged in to the Virtual

Technical College web site when you click on them to run. • To access and log in to the Virtual Technical College web site:

– To access the site type www.vtc.com in the url window– Log in using the username: CIS 1140 or ATCStudent1– Enter the password: student (case sensitive)

• If you should click on the demo link and you get an Access Denied it is because you have not logged in to vtc.com or you need to log out and log back in.

• If you should click on the demo link and you are taken to the VTC.com web site page you should do a search in the search box for the CompTIA Network+ (2009 Objectives) Course and run the video from within that page.

Objectives

• Explain basic data transmission concepts, including full duplexing, attenuation, and noise

• Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media

• Compare the benefits and limitations of different networking media

• Explain the principles behind and uses for serial connector cables

• Identify wiring standards and the best practices for cabling buildings and work areas

Transmission Basics

• In data networking, transmit means to issue signals to the network medium

• Transmission refers to either the process of transmitting or the progress of signals after they have been transmitted

• Transceiver– Transmits and receives signals

Cabling Demo

Cabling Basics Demo

Analog and Digital Signals

• Information transmitted via analog or digital signals– Signal strength proportional to voltage

• In analog signals, voltage varies continuously and appears as a wavy line when graphed over time– Wave’s amplitude (the height of the wave) is a measure of its

strength at given point in time– Frequency: number of times wave’s amplitude cycles from starting

point, through highest amplitude and lowest amplitude, back to starting point over a fixed period of time

• Measured in Hz– Wavelength: distance between corresponding points on a wave’s

cycle– Phase: progress of a wave over time in relationship to a fixed point• Analog transmission susceptible to transmission flaws such as noise

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An example of an analog signal

• Analog signal benefit over digitalo More variable

Convey greater subtleties with less energy• Drawback of analog signals

o Varied and imprecise voltage Susceptible to transmission flaws

Analog and Digital Signals• Digital signals composed of pulses of precise, positive voltages and

zero voltages– Positive voltage represents 1– Zero voltage represents 0

• Binary system: uses 1s and 0s to represent information– Easy to convert between binary and decimal

• Bit: a single binary signal• Byte: 8 bits

– Typically represents one piece of information• Overhead: describes non-data information that must accompany

data for a signal to be properly routed and interpreted

Transmission Direction: Simplex, Half-Duplex, and Duplex

• Simplex transmission: signals may travel in only one direction (TV or Radio)

• Half-duplex transmission: signals may travel in both directions over a medium – Only one direction at a time (Walkie Talkies

or Intercom System)• Full-duplex or duplex: signals free to travel in

both directions over a medium simultaneously (Telephone)– Used on data networks– Channel: distinct communication path

between nodes• May be separated logically or physically

Full Duplex vs Half Duplex Demo

Transmission Direction: Multiplexing

• Multiplexing: transmission form allowing multiple signals to travel simultaneously over one medium– Channel logically separated into subchannels

• Multiplexer (mux): combines multiple signals– Sending end of channel

• Demultiplexer (demux): separates combined signals and regenerates them in original form– Receiving end of channel

Relationships Between Nodes

•Point-to-point transmission involves only one transmitter and one receiver.•Point-to-multipoint transmission involves one transmitter and multiple receivers.•Broadcasts involve one transmitter and multiple, undefined receivers•Nonbroadcast point-to-multipoint transmission issues signals to multiple, defined recipients

Throughput and Bandwidth• Throughput: measure of amount of data transmitted during given

time period– Measured in bits per second, kilobits per second, megabits per second etc.– Probably most significant factor in choosing transmission method– Limited by signaling and multiplexing techniques used in given transmission

method– Transmission methods using fiber-optic cables achieve faster throughput than

those using copper or wireless connections– Noise and devices connected to transmission medium can limit throughput

• Bandwidth: difference between highest and lowest frequencies that a medium can transmit

– Range of frequencies– Measured in Hertz or cycles – 1 Hertz is the measure of a signal from its starting point to it’s highest amplitude

to it’s lowest amplitude and back to the starting point

Baseband and Broadband• Baseband: digital signals sent through direct current

(DC) pulses applied to a wire– Requires exclusive use of wire’s capacity– Baseband systems can transmit one signal at a time– Half-duplex or duplex transmission– Example: Ethernet

• Broadband: signals modulated as radiofrequency (RF) analog waves that use different frequency ranges– Does not encode information as digital pulses– Simplex transmission

Communication Methods Demo

Transmission Flaws: Noise• Electromagnetic interference (EMI): waves emanating from electrical

devices or cables

• Radio frequency interference (RFI): electromagnetic interference caused by radiowaves

• Crosstalk: signal traveling on a wire or cable infringes on signal traveling over adjacent wire or cable

• Certain amount of signal noise is unavoidable

• All forms of noise measured in decibels (dB)

Attenuation

A digital signal distorted by noise and then repeated

An analog signal distorted by noise and then amplified

Attenuation can be described as the loss of signal strength as the signal flows away from it’s source. It is caused by resistance on electrical networks and by optical loss on fiber optic networks.

Latency

• Delay between transmission and receipt of a signal– May cause network transmission errors– Many possible causes:

• Cable length• Intervening connectivity device (e.g., modems and

routers)• Round trip time (RTT): Time for packets to go from

sender to receiver and back• Cabling rated for maximum number of connected

network segments• Transmission methods assigned maximum segment

lengths

Network Cables

• A cable is the medium that provides the physical foundation for data transmission

• Several types of cable are commonly used• Some networks use only one type of cable, while others

employ several cable types• The type of cable chosen depends on:

– The size of the network– The protocols being used– The network’s physical layout, or topology

Network Transmission Media Demo

New and Old Cables and Connectors Demo

Common Media Characteristics: Throughput

• Probably most significant factor in choosing transmission methodo Match networking needs with media characteristics

• Limited by signaling and multiplexing techniques used in given transmission method

• Transmission methods using fiber-optic cables achieve faster throughput than those using copper or wireless connections

• Laws of Physics, noise, and devices connected to transmission medium can limit throughput

Cost• Precise costs difficult to pinpoint

• Media cost dependencies

– Existing hardware, network size, labor costs

• Variables influencing final cost of implementing specific type of media

– Installation cost

– New infrastructure cost versus reuse

– Maintenance and support costs

– Cost of lower transmission rate affecting productivity

– Cost of downtime

– Cost of obsolescence

Noise Immunity

• Noise distorts data signals– Distortion rate dependent upon transmission

media

• Fiber-optic: least susceptible to noise

• Limit noise impact on network– Cable installation

• Far away from powerful electromagnetic forces

– Select media protecting signal from noise– Antinoise algorithms

Size and Scalability

• Three specifications determine size and scalability of networking media:

– Maximum nodes per segment

• Depends on attenuation and latency

– Maximum segment length

• Depends on attenuation, latency, and segment type

• After certain distance, signal loses strength

– Cannot be accurately interpreted

• Populated segment contains end nodes

• Unpopulated: no end nodes

– Also called link segment

– Maximum network length

• Sum of network’s segment lengths

Media Distance and Speed Limitations (5:48)

Connectors and Media Converters• Connectors are the pieces of hardware that

connect the wire to the network device.

• Every medium requires a specific kind of connector

• Affect costs

• Installing and maintaining network

• Ease of adding new segments or nodes

• Technical expertise required to maintain network

• Media converter: hardware enabling networks or segments running on different media to interconnect and exchange signals

– Type of transceiver

• Device that transmits and receives signals Copper wire-to-fiber

media converter

Converting Media (5:10)

Coaxial CableCoaxial cable is an older technology that is usually implemented with a bus topology. It is not suitable for ring or star topologies because the ends of the cable must be terminated. It is composed of two conductors, which share a common axis, within a single cable.

Advantages Disadvantages

Highly resistant to EMI (electromagnetic interference)

Highly resistant to physical damage

Expensive

Inflexible construction (difficult to install)

Unsupported by newer networking standards

UTP, STP, and Coaxial Cabling (5:53)

Coaxial CableCoaxial cable is built with the following components:

•Two concentric metallic conductors:

– The inner conductor, which carries data signals. It is made of copper or copper coated with tin.

– The mesh conductor is a second physical channel that also grounds the cable. It is made of aluminum or copper coated tin.

•The insulator, which surrounds the inner conductor, keeps the signal separated from the mesh conductor. It is made of PVC plastic.

•The mesh conductor, which surrounds the insulator and grounds the cable. It is made of aluminum or copper coated tin.

•The PVC sheath, which is the cable encasement. It surrounds and protects the wire. It is made of PVC plastic.

Coaxial Cable Demo

Coaxial Cable Types The table below describes the different coaxial cable grades.

Grade Uses Resistance Rating

RG-5810Base2 Ethernet networking (also called Thinnet)

50 ohms

RG-59 Cable TV and cable networking 75 ohms

RG-6

Cable TV, satellite TV, and cable networkingRG-6 has less signal loss than RG-59, and is a better choice for networking applications, especially where longer distances (over a few feet) are involved.

75 ohms

RG-810Base5 Ethernet networking (also called Thicknet)

50 ohms

When using coaxial cables, it is important to use cables with the same resistance (impedance) rating.

Coaxial Connectors• Connectors: pieces of hardware connecting wire to

network device– Every networking medium requires specific kind of connector

Connectors Demo

Connector Description

• Twisted onto the cable • Used to create cable and satellite TV

connections • Used to connect a cable modem to a

broadband cable connection

                                           

• Molded onto the cable • Used in 10Base2 Ethernet networks

F-type connector

BNC

Connector Description

• A DB15 serial connector serves as the attachment unit interface (AUI) on the NIC and on the transceiver

• Requires a drop cable from the NIC to the transceiver

• Connected to the transceiver is a Vampire Tap with a screw or “tooth” that pierces the cable to connect to the conducting core of a thick coaxial cable

• Used in 10Base5 Ethernet networks

Coaxial Connectors

10BASE5 vampire tap & transceiver

AUI

Coaxial Cable Networks

• Thin Ethernet, Thinnet, or Black Ethernet: more flexible and easier to handle and install than Thicknet– 10BASE-2 Ethernet– Requires RG-58 A/U coaxial cable, BNC-T connectors– Each end of the cable segment must be terminated with a 50 ohm resistor– Conforms to the 5-4-3 Rule of network which states that a network can

contain up to 5 cable segments, connected by 4 repeating devices, but only three of the cable segments can contain end nodes.

Coaxial Cable Networks

• Thickwire Ethernet, Thicknet, Yellow Ethernet: original Ethernet medium– 10BASE-5 Ethernet Standard– Requires RG-8 coaxial cable, AUI connectors, Transceiver/Vampire Tap, and Drop cable.– Each end of the cable segment must be terminated with a 50 ohm resistor– Conforms to the 5-4-3 Rule of network which states that a network can contain up to 5 cable segments,

connected by 4 repeating devices, but only three of the cable segments can contain end nodes.

Twisted-Pair Cable

Twisted pair cables support a wide variety of fast, modern network standards. Twisted pair cabling is composed of the following components:

•Two wires that carry the data signals (one conductor carries a positive signal; one carries a negative signal). They are made of 22 or 24 gauge copper wiring.

•PVC or plenum plastic insulation surrounds each wire. Plenum cable is fire resistant and non-toxic. It must be used when wiring above ceiling tiles. PVC cable cannot be used to wire above ceilings because it is toxic when burned.

•Two wires are twisted to reduce the effects of electromagnetic interference (EMI) and crosstalk. Because the wires are twisted, EMI should affect both wires equally and can be cancelled out.

– The number of twists per meter or foot determines how resistant the pair will be to noise but increases attenuation

• TIA/EIA 568 standard divides twisted-pair wiring into several categories• Level 1 or CAT 3, 4, 5, 5e, 6, 6e, 7

Cable Categories (3:34)

Twisted-Pair Cable• Advantages:

o Is relatively inexpensive, easy to install, and capable of spanning significant distances before additional equipment is required

o Can accommodate several different topologies, but is most often used in a star topology

o Can handle the faster networking transmission rates in use today

• Multiple wire pairs are bundled together in an outer sheath. Twisted pair cable can be classified according to the makeup of the outer sheath:

– Shielded Twisted Pair (STP) has a grounded outer copper shield around the bundle of twisted pairs or around each pair. This provides added protection against EMI.

– Unshielded Twisted Pair (UTP) does not have a grounded outer copper shield. UTP cables are easier to work with and are less expensive than shielded cables.

Twisted Pair Cabling and Connectors Demo

UTP Cable Demo

Shielded Twisted-Pair (STP)• Shielded Twisted-Pair (STP):

– The cable consists of insulated wire pairs that are surrounded by a metal shielding, such as foil

– The effectiveness of the shield depends on the environmental noise to which STP is subjected, the grounding mechanism, and the material, thickness, symmetry and consistency of the shielding

– Barrier to external electromagnetic forces– Contains electrical energy of signals inside– STP is more expensive than UTP, but does provide better

immunity to EMI and RFI

STP cableSTP Cable Demo

UTP (Unshielded Twisted-Pair)• Less expensive, less resistant to noise than STP

– The cable contains color-coded pairs of insulated copper wires inside a plastic jacket

– Each pair has a different number of twists per inch, depending on the grade, to help eliminate interference from adjacent pairs or cables

• Categories:– CAT 3 (Category 3): up to 10 Mbps of data at

16 MHz– CAT 4 (Category 4): 16 Mbps throughput at up

to 20 MHz– CAT 5 (Category 5): up to 1000 Mbps

throughput at 100 MHz– CAT 5e (Enhanced Category 5): higher twist

ratio 350 MHz– CAT 6 (Category 6): six times the throughput of

CAT 5. Wires encased in foil. 250 MHz– CAT 6e (Enhanced Category 6): reduced

attenuation and crosstalk. Capable of 550 MHz.– CAT 7 (Category 7): signal rates up to 1 GHz.

Contains sheilding and uses different connectors.

Twisted Pair Connectors

Connector Description

RJ-11                       

•Has 4 connectors •Supports up to 2 pairs of wires •Uses a locking tab to keep connector secure in outlet •Used primarily for telephone wiring

RJ-45                               

•Has 8 connectors •Supports up to 4 pairs of wires •Uses a locking tab to keep connector secure in outlet •Used for Ethernet and some token ring connections

Copper Connectors (10:29)

Comparing STP and UTP Characteristics

• Throughput: STP and UTP can both transmit data at 10, 100, and 1000 Mbps – Depending on grade of cabling and transmission

method used• Cost: STP usually more expensive than UTP• Connector: Both use RJ-45 for data and RJ-11 for

phones• Noise Immunity: STP more noise-resistant• Size and scalability: Max segment length for both is 100

meters– Maximum of 1024 nodes

Terminating Twisted Pair Cable

• Patch cable– Relatively short cable– Connectors at both ends

• Proper cable termination techniques– Basic requirement for two nodes to communicate

• Poor terminations:– Lead to loss or noise

• TIA/EIA standards– TIA/EIA 568A– TIA/EIA 568B

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TIA/EIA 568A Series

In the T568A standard the green and green and white striped wire transmits data from the device, while the orange wire and the orange and white striped wire receives data from the network.

TIA/EIA 568A standard terminations

TIA/EIA 568B Series

• In the T568B standard the orange and orange and white striped wire transmits data from the device, while the green wire and the green and white striped wire receives data from the network.

• It typically doesn’t matter which scheme you choose, but to avoid confusion and potential transmission errors you should ensure that you cable all wiring on your LAN according to one standard. TIA/EIA 568B standard terminations

Straight-Through Cable

Cable Description

Straight-through

Computers connect to the network through a hub or switch with a straight-through cable. There are two standards for creating straight-through cables: T568A--To use this standard, arrange the wires from pins 1 to 8 in each connector in the following order: GW, G, OW, B, BW, O, BrW, Br.

T568B--To use this standard, arrange the wires from pins 1 to 8 in each connector in the following order: OW, O, GW, B, BW, G, BrW, Br.

It doesn't matter which standard you use, but once you choose a standard, you should do all your cables that way to avoid confusion during troubleshooting.

Crossover and Straight Through Cables (6:27)

Crossover Cable

•Crossover cables are used to wire two computer’s network cards together without the use of a hub/switch or to wire two hubs/switches together through their data ports (stacking)•To create a crossover cable wire one end of the cable 568A and the other end 568B

Device ConnectionWhen connecting Ethernet devices, it is important that the transmit (Tx) wires from one device are matched with the receive (Rx) wires on the other device. To help understand how to connect devices together, be aware of the following:•Network interface cards in workstations and routers send data on the transmit pins and expect to receive data on the receive pins. •Between any two ports used for connecting devices to a hub or a switch, crossing is automatically performed within the hub or the switch. •Uplink ports on hubs and switches are not crossed.

Cable Type - Usage

Cable Type Use

Straight-through

A straight-through cable connects each wire to the same pin on each connector (pin 1 to pin 1, pin 2 to pin 2, etc.). Use a straight-through cable when the crossover is performed with a hub or a switch. Use a straight-through cable when connecting the following devices:

Workstation to a regular port on a hub or switch

Router to a regular port on a hub or a switch

Regular port on a hub or switch to an uplink port on a hub or a switch

Crossover

A crossover cable matches the transmit (Tx) wires on one connector with the receive (Rx) wires on the other connector. Use a crossover cable when crossing is not performed automatically, or when crossover is being performed twice. Use a crossover cable when connecting the following devices: Workstation to a workstation, router to a router, or workstation to a router (in a back-to-back configuration)

Uplink port on a hub or a switch to an uplink port on a hub or a switch

Workstation or a router to the uplink port on a hub or a switch

Hub or switch using a regular port to a hub or a switch using the regular port

Straight-through Patch Cable Assembly Instructions

• Strip the cable jacket back about 3/4 of an inch from the end of the cable

• Sort the pairs so they fit into the connector in the correct order

• Insert the pairs into the connector

• Crimp the pins with a crimp tool

• Repeat for other end and test cable

Twisted Pair Wiring Tools

• Termination tools– Wire cutter– Wire stripper– Crimping tool

• After making cables:– Verify data transmit and receive

Crimpers (3:36)

Fiber-Optic CableTo connect computers using fiber optic cables, you need two fiber strands. One strand transmits signals, and the other strand receives signals. Fiber optic cabling is composed of the following components:•Fiber-optic cable (fiber)

– One or more glass or plastic fibers at its center (core) carries the signal•Cladding

– The cladding maintains the signal in the center of the core as the cable bends. It is made of a different density of plastic or glass.

•Kevlar strands

– Give the cable strength and allow it to avoid stretching

•A Plastic sheath covers the kevlar strands and protects the cladding and the core

•Data transmission– Pulsing light sent from laser or light-emitting diode (LED) through central

fibers

44A fiber-optic cable

Fiber-Optic Cable

Fiber Optic Cable Demo

Advantages Disadvantages

Totally immune to EMI (electromagnetic interference)

Highly resistant to eavesdropping

Supports extremely high data transmission rates

Allows greater cable distances without a repeater

Industry standard for high-speed networking

Very expensive

Difficult to work with

Special training required to attach connectors to cables

Fiber Optic Characteristics• Throughput

– transmission rates exceed 10 Gigabits per second• Cost

– most expensive of the transmission mediums• Connector

– 10 different types of connectors– typically use ST, SC, LC, or MTRJ connectors

• Noise immunity– unaffected by EMI, RFI, or crosstalk

• Size and scalability– segment lengths vary from 150 to 40,000 meters– Suffers from optical loss

• degradation of light signal after it travels a certain distance away from its source

Fiber Optic Cables

Type Description

Single Mode(SMF)

Multi-mode(MMF)

• Transfers data through the core using multiple light rays • The core diameter is around 50 to 100 microns • Cable lengths are limited in distance• Common uses

– Cables connecting router to a switch– Cables connecting server on network backbone

• Transfers data through the core using a single light ray (the ray is also called a mode)

• The core diameter is around 10 microns • Supports a large amount of data • Cable lengths can extend a great distance• Rarely used for shorter connections

– Due to cost

Multimode and Singlemode Fiber (4:46)

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Figure 3-36 MT-RJ (mechanical transfer-register jack) connector

Figure 3-35 LC (local connector)

Figure 3-33 ST (straight tip) connector

Figure 3-34 SC (subscriber connector or standard connector)

Fiber Optic Connectors

Fiber Connectors (4:36)

Fiber-Optic Converters

• Required to connect multimode fiber networks to single-mode fiber networks– Also fiber- and copper-based parts of a

network

49

Single-mode to multimode converter

Courtesy Omnitron Systems Technology

Serial Cables

Figure 3-37 DB-9 connector Figure 3-38 DB-25 connector

• Data transmission style- Pulses issued sequentially, not simultaneously

• RS-232 (Recommended Standard 232)–EIA/TIA standard–Physical layer specification

• Signal voltage, timing, compatible interface characteristics–Connector types

• RJ-45 connectors, DB-9 connectors, DB-25 connectors• RS-232 used between PC and router today• RS-232 connections

–Straight-through, crossover, rollover

Structured Cabling• Structured cabling specifies standards without

regard for the type of media or transmission technology used on the network.

• Structured cabling is based on a hierarchical design that divides cabling into subsystems.

• You should be familiar with the principles of structured cabling before you attempt to design, install, or troubleshoot an organization’s cable plant.

• Cable plant– hardware making up enterprise-wide cabling

system

Structured Cabling

TIA/EIA structured cabling in an enterprise

• Components

– Entrance facilities

– MDF (main distribution frame)

– Cross-connect facilities

– IDF (intermediate distribution frame)

– Backbone wiring

– Telecommunications closet

– Horizontal wiring

– Work area

TIA/EIA specifications for backbone cabling

Entrance facilities or Demarcation point (demarc)

When you contract with a local exchange carrier (LEC) for data or telephone services, they install a physical cable and a termination jack (Smart Jack) onto your premises. The demarcation point (demarc) is the line that marks the boundary between the telco equipment and the private network or telephone system. •Typically, the LEC is responsible for all equipment on one side of the demarc, and the customer for all equipment on the other side of the demarc. •The demarc is typically located in the bottom floor of a building, just inside the building. •The demarc is often identified by an orange plastic cover on the wiring component.

Demarcs and Smart Jacks (3:39)

Main Distribution Frame (MDF)

The main distribution frame (MDF), also known as the main cross-connect or the Equipment room, is the main wiring point for a building.

The MDF is the interconnection point between the LAN/WAN and the service provider’s facility.

The MDF is typically located on the bottom floor or basement. The LEC typically installs the demarc to the MDF.

The location of significant networking hardware, such as servers and mainframe hosts.

IDF and MDF (3:33)

Intermediate Distribution Frame (IDF) or Telecommunications Closet

An intermediate distribution frame (IDF) is a smaller wiring distribution point within a building. IDFs are typically located on each floor directly above the MDF, although additional IDFs can be added on each floor as necessary.

The IDF or telecommunications closet contains connectivity for groups of workstations in an area, plus cross connections to equipment rooms

Backbone Wiring

Backbone wiring or Vertical cross-connect: interconnection between telecommunications closets, equipment rooms, and entrance facilities

Vertical cross connect

A vertical cross connect connects the MDF on the main floor to IDFs on upper floors. Cabling runs vertically (up and down) between the MDF and the IDFs.

Horizontal cross connect

A horizontal cross connect connects IDFs on the same floor. Cabling runs horizontally (sideways) between the IDFs.

Work Area

The Work Area encompasses all patch cables and horizontal wiring necessary to connect workstations, printers, and other network devices from NICs to telecommunications closet

TIA/EIA structured cabling in a building

Horizontal Wiring

Horizontal wiring is the wiring connecting workstations to the closest telecommunications closet

Horizontal Wiring Subsystem

Horizontal wiring subsystem —TIA/EIA recognizes three possible cabling types for horizontal wiring: STP, UTP, or fiber-optic. The maximum allowable distance for horizontal wiring subsystem is 100 m. This span includes 90 m to connect a data jack on the wall to the telecommunications closet plus a maximum of 10 m to connect a workstation to the data jack on the wall plus the cross connect.

Patch panel Patch panel

A patch panel is a device that typically connects individual stranded wires into female RJ-45 connectors. For example, you might connect 4 pairs of wires from a punchdown block to a port on the patch panel. On the patch panel, you then connect drop cables (cables with RJ-45 connectors) to the patch panel on one end and a computer on the other end.

Wiring Rack

Punchdown block

Patch Panel

“Telco Room”

Only twisted pair can be terminated in the punch down block.

Data Outlet

Data Outlet

Installing Cable• Many network problems can be traced to poor cable installation

techniques• Two methods of inserting UTP twisted pairs into RJ-45 plugs: TIA/EIA

568A and TIA/EIA 568B• Straight-through cable allows signals to pass “straight through” between

terminations. Straight-through cables are used when connecting a PC to a Hub or Switch or when connecting Hubs together through their uplink ports.

• Crossover cable: termination locations of transmit and receive wires on one end of cable reversed. Crossover cables are used when connecting a PC directly to another PC without going through a Hub or when connecting or “stacking” two hubs together through their data ports.

• Installation tips to prevent Physical layer failures– See Pages 121-122 in the text

Plenum and Non-Plenum Cabling (4:22)

Summary• Information can be transmitted via two methods: analog

or digital• In multiplexing, the single medium is logically separated

into multiple channels, or subchannels• Throughput is the amount of data that the medium can

transmit during a given period of time• Baseband is a form of transmission in which digital

signals are sent through direct current pulses applied to the wire

• Noise is interference that distorts an analog or digital signal

• Analog and digital signals may suffer attenuation• Cable length contributes to latency, as does the

presence of any intervening connectivity device

Summary (continued)• Coaxial cable consists of a central copper core surrounded by a

plastic insulator, a braided metal shielding, and an outer plastic cover (sheath)

• Twisted-pair cable consists of color-coded pairs of insulated copper wires

• There are two types of twisted-pair cables: STP and UTP• There are a number of Physical layer specifications for Ethernet

networks• Fiber-optic cable provides the benefits of very high throughput, very

high resistance to noise, and excellent security• Fiber cable variations fall into two categories: single-mode and

multimode• Structured cabling is based on a hierarchical design that divides

cabling into subsystems• The best practice for installing cable is to follow the TIA/EIA 568

specifications and the manufacturer’s recommendations

The End