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Networking Basics CCNA 1 Chapter 3

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Title: Networking Basics CCNA 1 Chapter 3


1
Networking Basics CCNA 1 Chapter 3
2
Networking Media
  • Digital Transmission Can be Done in Many Ways
  • By varying (modulating) an electrical signal as
    it passes over a copper wire
  • By varying (modulating) the power of light as
    sent over a glass optical fiber
  • By varying (modulating) the radio waves sent
    through space, which is commonly referred to as
    wireless communications

3
Copper Media
  • Most common type of cables use twisted pairs of
    copper wires
  • Must understand the basics of electricity,
    similar to an introductory physics or chemistry
    class

4
Copper Media
  • The Chemistry Behind Electricity Atoms and
    Electrons
  • Protons Particles that have a mass equal to a
    neutron, with a positive electrical charge
  • Neutrons Particles with a mass equal to a
    proton, but with no electrical charge
  • Electrons Particles that have negligible mass,
    but have a negative charge equal in strength to a
    protons positive charge

5
Copper Media
  • The Chemistry Behind Electricity The Periodic
    Table

6
Copper Media
  • The Chemistry Behind Electricity The Periodic
    Table
  • Each type of atom, called an element, has a
    different number of protons
  • Atoms have a nucleus composed of protons and
    neutrons
  • Since atoms have equal numbers of protons and
    electrons, their net charge is 0

7
Copper Media
  • The Chemistry Behind Electricity The Bohr Model
    of a Helium Atom

8
Copper Media
  • Forces That Keep Atoms Stable
  • Opposite charges attract, like charges repel
  • Works like magnets
  • Strong nuclear forces also exist (like gravity
    inside the nucleus)
  • Electrons generate centrifugal force
  • The attraction of the proton and electron
    balances the electrons centrifugal force

9
Copper Media
  • How Releasing Electrons Creates Electrical
    Current
  • Electrical current can be made to flow over a
    wire by making the atoms free their electrons
  • Freed electrons move down the copper wire
  • The electrical charges move down the wire at
    nearly 70 the speed of light in a vacuum
  • As one electron is freed, it exerts force on
    other atoms
  • This causes other electrons to be freed
  • The process continues

10
Copper Media
  • Electrostatic Discharge and Static Electricity
  • If freed electrons do not re-attach to an atom,
    static electricity is formed
  • When these freed electrons jump to a conductor,
    it leads to electrostatic discharge (ESD)
  • ESD does not harm people, but it can harm
    electronics
  • Computer chips are extremely sensitive to ESD
  • Take safety precautions before working inside
    computers, routers, and other electronic devices

11
Copper Media
  • Three Main Types of Electrical Materials

12
Copper Media
  • Three Main Types of Electrical Materials
  • Insulators require a great deal of force to move
    their electrons from orbit
  • Conductors require little force to move their
    electrons from orbit
  • Semiconductors can be precisely controlled as to
    when their electrons leave orbit

13
Copper Media
  • Electromagnetic Force (Voltage)
  • Electromotive force (EMF) causes electrons to
    leave their orbits and create a wave of
    electrical current down a wire
  • EMF is better known as voltage
  • The unit of measure for EMF (voltage) is volt (V)

14
Copper Media
  • Current
  • Current is measured in amperes (amps)
  • Current is the number of charges per second that
    pass by a point along a path

15
Copper Media
  • Types of Current
  • Direct Current (DC) Movement of electrons
    always flows in a single direction from negative
    terminal to positive terminal
  • Alternating Current (AC) Movement of electrons
    and current changes direction, because the
    terminals of the AC voltage source regularly
    change from negative to positive and back again

16
Copper Media
  • Creating Electrical Energy Using Voltage and
    Current
  • Electrical energy is called wattage
  • Wattage equals Voltage times Amperage
  • (W V I)
  • Static electricity has high voltage but very low
    current
  • Lightning has high voltage and high current
  • Which is more dangerous?

17
Copper Media
  • Resistance, Impedance and Attenuation
  • Resistance is the property of a material that
    resists electron movement measured in Ohms and
    expressed as R or the Greek letter omega
  • Voltage Current times Resistance
  • (V I R)
  • This is known as Ohms Law

18
Copper Media
  • Electrical Characteristics and Units of
    Measurement

19
Copper Media
  • Electrical Characteristics and Units of
    Measurement
  • All materials have some amount of resistance
  • The term impedance is used to define the
    combined resistive forces in an AC circuit
  • Resistance and perhaps impedance cause a signal
    to degrade
  • Signal degrades as it travels across a copper
    cable this is called attenuation
  • Attenuation is why cables are restricted to some
    maximum length

20
Copper Media
  • Circuits consist of a conductive material
    through which an electrical current can flow
    Illustration of a flashlight turned off and
    turned on
  • Bulb converts some electrical energy into light
    and some into heat
  • Bulb adds resistance to circuit

21
Copper Media
  • Alternating current as graphed by an oscilloscope

22
Copper Media
  • Alternating current as graphed by an oscilloscope
    (continued)
  • X-axis represents time
  • Y-axis represents voltage
  • Usually two y-axis inputs so two circuits can be
    simultaneously displayed
  • Electricity flows to ground because the Earth
    can conduct electricity, it can be part of an
    electrical circuit

23
Copper Media
  • Popular LAN Copper Cabling
  • The Telecommunications Industry Association (TIA)
    and the Electronic Industries Alliance (EIA) have
    jointly defined cabling standards
  • Most popular standard is TIA/EIA-568-B, which
    defines commercial building telecommunication
    standards
  • TIA/EIA-568-B defines rules and requirements for
    using unshielded twisted-pair cabling and how to
    use the pins on the connectors

24
Copper Media
  • Popular LAN Copper Cabling
  • The Institute of Electrical and Electronic
    Engineers (IEEE) defines LAN standards such as
    the 802.3 standard used for Ethernet
  • Points of comparison for networking cable
  • What data transmission speeds can be achieved?
  • Will transmissions be digital or analog?
  • How far can a signal travel before attenuation
    becomes a concern?

25
Copper Media
  • Popular LAN Copper Cabling
  • IEEE 802.3 defines several Ethernet types
  • 10BASE5
  • 10BASE2
  • 10BASE-T
  • The 10 means 10 Mbps transmission rate, the 5
    and 2 refer to cable length (approx. 500 and
    185 meters), BASE refers to the cable type, and
    T to UTP cabling

26
Copper Media
  • Coaxial Cable
  • Four main parts
  • Copper conductor
  • Plastic insulation
  • Braided copper shielding
  • Outer jacket

27
Copper Media
  • Coaxial Cable
  • Coax is no longer used, but it has several
    advantages
  • Can run for longer distances without need for
    repeaters
  • Less expensive than fiber-optic cable, although
    more expensive than UTP and STP

28
Copper Media
  • Shielded Twisted-Pair (STP) Cable
  • STP includes shielding UTP does not
  • Three types of insulation
  • Each single wire is covered with color-coded
    plastic insulation
  • Each pair of wires is twisted together with an
    insulator called a pair shield around them
  • All the wires in the cable (usually 4 pairs) are
    covered by a shield called the overall shield

29
Copper Media
  • Shielded Twisted-Pair (STP) Cable

30
Copper Media
  • Screened Twisted-Pair (ScTP) Cable

31
Copper Media
  • Unshielded Twisted-Pair (UTP) Cable

32
Copper Media
  • Unshielded Twisted-Pair (UTP) Cable Has Many
    Advantages
  • It does not require grounding like STP cables do
  • Easiest to add connectors to ends
  • Relatively small diameter makes it more flexible
    and more can fit into a conduit
  • Supports the same data speeds as other copper
    media

33
Copper Media
  • LAN UTP Cabling Standards
  • Ethernet became the predominant LAN standard in
    the 1990s
  • Speeds have increased from 10 Mbps to 1 Gbps and
    even faster
  • Standards committees had to specify how the
    cables would work to support higher speeds
  • TIA/EIA has standards for different Ethernet types

34
Copper Media
  • LAN UTP Cabling Standards (continued)

35
Copper Media
  • UTP Cable Pinouts
  • Each end of a UTP cable has a registered jack 45
    (RJ-45) connector installed
  • The connector has 8 numbered slots into which the
    8 wires in the cable are installed
  • The 8 wires must be installed in a specific
    order this is called the pinout
  • 10- and 100-Mbps Ethernet devices use one pair of
    wires to transmit
  • 10- and 100-Mbps Ethernet devices do not use the
    same pair to transmit and receive, so two pairs
    of wires are needed

36
Copper Media
  • RJ-45 Connectors

37
Copper Media
  • Ethernet Straight-Through Cables and Pinouts
  • A typical Ethernet cable between an end-user
    device and a LAN hub or switch is a
    straight-through cable

38
Copper Media
  • A PCs NIC uses this logic
  • Send on the pair at pins 1 and 2 of the RJ-45
    connector
  • Expect to receive electrical current on the pair
    of wires at pins 3 and 6
  • A Hub uses this logic (the opposite of a NIC)
  • Send on pins 3 and 6
  • Receive signals on pins 1 and 2

39
Copper Media
  • TIA Standard Pinouts

40
Copper Media
  • TIA/EIA Standard Pinouts (use 568-A or 568-B at
    both ends) to create a straight-through cable

41
Copper Media
  • Crossover Cable Pinouts
  • Similar devices, such as 2 PCs with NICs, expect
    to transmit on pins 1 and 2 and receive on pins 3
    and 6
  • The pairs at one end must be switched (crossed
    over) to allow communication

42
Copper Media
  • TIA/EIA-568-B Crossover Cable Pinouts

43
Copper Media
  • Console Connections and Rollover Cables
  • Wire on pin 1 on one end connects to pin 8 on the
    other end pin 2 connects to pin 7, pin 3 to pin
    6, etc.
  • Rollover cables are used to connect to a serial
    port on a computer and a console port on a Cisco
    router or switch, allowing the user to configure
    the device

44
Copper Media
  • Choosing the Correct Cabling Pinouts
  • When connecting two devices that are similar in
    regard to the pins they use to transmit, use a
    crossover cable
  • When connecting two devices that differ in regard
    to the pins they use to transmit, use a
    straight-through cable
  • Which devices use which pins to transmit
  • Pins 1 and 2 PCs, routers, servers, wireless
    access points Ethernet ports
  • Pins 3 and 6 Switches, hubs, and bridges

45
Optical Media
  • Fiber-Optic Cabling
  • Uses glass fibers to transmit light
  • The transmitter varies the light, which the
    receiver interprets as 1s and 0s
  • Typically uses infrared light
  • Do NOT look into an end of a fiber optic cable
    that has the other end plugged into a networking
    device!!!!!!!!

46
Optical Media
  • Comparing Fiber-Optic Cabling and Copper Cabling
  • Fiber is not susceptible to lightning,
    electromagnetic interference (EMI) or radio
    frequency interference (RFI)
  • Fiber has much greater bandwidth capabilities
    than other media
  • Fiber allows much longer transmission distances
  • Fiber is more secure because it is more difficult
    to tap into
  • Fiber transmitters and receivers can be updated
    but will still work with existing fiber

47
Optical Media
  • Comparing Fiber-Optic Cabling to Copper Cabling
    (continued)
  • Sand, which is plentiful, is the raw material
    used to make fiber-optic cable
  • Fiber has no electrical signal, so grounding is
    not required
  • Fiber cable has a small diameter, requiring
    little space in a conduit
  • The cable is lightweight, which makes
    installation easier
  • Fiber has better resistance to environmental
    factors
  • Lengths of fiber can be spliced for long runs

48
Optical Media
  • Electromagnetic Spectrum
  • Light is pure energy and can pass through many
    different media
  • Light can be absorbed and reflected
  • Light travels as a wave

49
Optical Media
  • Electromagnetic Spectrum
  • Characteristic of Light
  • Wavelength the length of one complete wave
    cycle
  • Frequency the number of times a repeating part
    of the graph (wave) occurs in one second
  • Digital transmissions over optical cabling use
    these infrared wavelengths
  • 850 nm
  • 1310 nm
  • 1550 nm

50
Optical Media
  • Electromagnetic Spectrum

51
Optical Media
  • Fiber-Optic Cabling
  • Devices modulate infrared light over a glass
    fiber in the middle of a cable
  • Bright light means a 1, dim light means a 0
  • Do not pass any electricity
  • Less susceptible to interference

52
Optical Media
  • Fiber-Optic Cabling
  • Use two fibers one for each direction
  • Cables are marked Tx for transmit and Rx for
    receive
  • The Tx on one end connects to the Rx on the other
    end
  • The transmitter is a light-emitting diode (LED)
    and the receiver is a p-intrinsic-n diode (PIN
    photodiode or simply photodiode)

53
Optical Media
  • Fiber-Optic Cabling Components
  • Core glass-like material called silicon
    dioxide the light travels through the core
  • Cladding surrounds the core to reflect light
    back into the core
  • Buffer surrounds the cladding to provide
    physical protection to cladding and core
  • Strengthening material often made of Kevlar
  • Outer jacket surrounds the cable to protect it
    from abrasion, solvents, and other contaminants

54
Optical Media
  • Five Elements of a Fiber-Optic Cable

55
Optical Media
  • Multimode and Single-Mode Fiber
  • General characteristics
  • Less expensive LED transmitters are used with
    relatively less expensive multimode cabling
  • More expensive Laser transmitters are used with
    the more expensive single-mode cables
  • Single mode cables, with laser transmitters,
    support significantly longer cabling distances
    than multimode using LEDs

56
Optical Media
  • Multimode and Single-Mode Fiber
  • General characteristics (continued)
  • LEDs emit light in many directions while lasers
    emit light in a straight line
  • When using LEDs, some of the light doesnt make
    it into the cable
  • Light can enter multimode cables at different
    angles
  • Lasers transmit the light down the center of the
    cable and the light can travel farther

57
Optical Media
  • Single-Mode Fiber versus Multimode Fiber

58
Optical Media
  • Comparing the Diameters of Single-Mode Fiber and
    Multimode Fiber

59
Wireless Media
  • Electricity cannot pass through the air, so a
    conductor like a copper wire is required
  • Infrared energy can go through the air, but it
    doesnt pass through solid objects well
  • Wireless media does not use wire or cable of any
    kind it sends data using radio waves
  • Radio waves can pass through some solid materials

60
Wireless Media
  • Enterprise WLAN Components and Design
  • To create a wireless LAN, these components are
    required
  • PCs with WLAN NICs
  • Access Points (APs), which act as a LAN hub for
    wireless devices

61
Wireless Media
  • Enterprise WLAN Components and Design Wireless
    NIC and Access Point

62
Wireless Media
  • Typical Enterprise WLAN Design

63
Wireless Media
  • Installation of an Enterprise WLAN
  • To install a WLAN that works with an existing
    LAN infrastructure, you need
  • A least one AP
  • A straight-through cable to connect the AP to an
    existing LAN switch
  • Wireless NICs in end-user devices so the devices
    can communicate with the APs

64
Wireless Media
  • Enterprise WLAN Characteristics
  • Use overlapping service areas called cells, which
    allows users to roam without losing connectivity
  • Multiple APs allow a user device to select the
    connection with the best signal strength and then
    associate with it
  • Active scanning causes a NIC to send a probe
    request which contains a Service Set Identifier
    (SSID)
  • Passive scanning listens for frames sent by APs
  • Any two devices can find each other and form an
    ad hoc network

65
Wireless Media
  • WLAN Organizations and Standards
  • The IEEE defines WLAN standards as part of the
    802.11 committee
  • The most common WLAN standards are 802.11a,
    802.11b, and 802.11g
  • All devices must comply with rules concerning
    radio transmission - in the US, the Federal
    Communications Commission sets the standards
  • Since cells are shared, collisions can occur
    WLANs use carrier sense multiple access with
    collision avoidance (CSMA/CA) to avoid collisions

66
Wireless Media
  • WLAN Organizations and Standards (continued)
  • The 802.11 standard defines two physical layer
    transmission options
  • Frequency Hopping Spread Spectrum (FHSS)
  • Direct Sequence Spread Spectrum (DSSS)
  • Later standards used a new method called
    Orthogonal Frequency Division Multiplexing (OFDM)

67
Wireless Media
  • WLAN Organizations and Standards (continued)

68
Summary
  • Copper cable carries information using electrical
    current
  • It is helpful to understand these electrical
    concepts
  • Voltage the pressure that moves electrons
  • Resistance opposition to the flow of electrons
  • Current flow of charges created when current
    moves
  • Circuit closed loop through which an electric
    current flows

69
Summary
  • Circuits must have conducting materials and
    sources of voltage
  • Voltage causes current to flow, while resistance
    and impedance oppose it
  • LAN standards define the use of coaxial cable,
    UTP cable, and STP cable, with UTP being the most
    commonly used
  • Twisted-pair cables often use RJ-45 connectors
  • Straight-through cables are used to connect
    unlike devices, such as a PC and a switch

70
Summary
  • Crossover cables are used to connect similar
    devices, such as two switches
  • A rollover cable is used to connect a serial port
    on a PC to a console port on a Cisco router or
    switch
  • Optical fiber cable is used for longer,
    high-bandwidth, point-to-point connects on LAN
    backbones and WANs.
  • A transmitter is used on one end of a fiber cable
    and a receiver on the other end
  • Two cables are used for connections between
    devices - one for each direction

71
Summary
  • There are five main parts to optical fiber
    cabling
  • The core, which is the center where the light
    shines through
  • The cladding, which reflects light back into the
    core
  • The buffer, to provide protection and strength
  • Strengthening material, containing Kevlar
  • The outer insulation to provide protection from
    abrasion and solvents
  • Light in a cable follows paths called modes
  • A fiber that is large enough to allow light to
    take many paths is called multimode fiber
  • A fiber that limits light to a single path is
    called single-mode fiber

72
Summary
  • Single-mode fiber is capable of longer
    transmission distances than multimode fiber
  • Single-mode fiber is capable of higher data
    transmissions rates than multimode fiber
  • A WLAN can consist of as few as two devices
  • A WLAN infrastructure mode can be set up by using
    an AP as a central hub for the WLAN
  • IEEE standards for wireless include 802.11a,
    802.11b, and 802.11g. 802.11a uses frequencies in
    the 5 GHz band, while the other two use 2.4 GHz
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