Networking Basics CCNA 1 Chapter 3

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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

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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

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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

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Copper Media

• The Chemistry Behind Electricity The Periodic
  Table

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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

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Copper Media

• The Chemistry Behind Electricity The Bohr Model
  of a Helium Atom

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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

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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

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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

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Copper Media

• Three Main Types of Electrical Materials

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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

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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)

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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

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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

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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?

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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

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Copper Media

• Electrical Characteristics and Units of
  Measurement

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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

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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

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Copper Media

• Alternating current as graphed by an oscilloscope

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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

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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

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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?

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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

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Copper Media

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

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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

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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

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Copper Media

• Shielded Twisted-Pair (STP) Cable

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Copper Media

• Screened Twisted-Pair (ScTP) Cable

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Copper Media

• Unshielded Twisted-Pair (UTP) Cable

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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

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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

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Copper Media

• LAN UTP Cabling Standards (continued)

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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

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Copper Media

• RJ-45 Connectors

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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

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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

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Copper Media

• TIA Standard Pinouts

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Copper Media

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

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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

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Copper Media

• TIA/EIA-568-B Crossover Cable Pinouts

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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

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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

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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!!!!!!!!

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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

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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

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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

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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

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Optical Media

• Electromagnetic Spectrum

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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

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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)

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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

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Optical Media

• Five Elements of a Fiber-Optic Cable

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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

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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

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Optical Media

• Single-Mode Fiber versus Multimode Fiber

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Optical Media

• Comparing the Diameters of Single-Mode Fiber and
  Multimode Fiber

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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

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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

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Wireless Media

• Enterprise WLAN Components and Design Wireless
  NIC and Access Point

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Wireless Media

• Typical Enterprise WLAN Design

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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

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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

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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

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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)

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Wireless Media

• WLAN Organizations and Standards (continued)

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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

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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

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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

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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

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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