Chapter 3 Physical Components of a Network

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Chapter 3Physical Components of a Network

• 3.1 Configuring a Network Interface Card
• 3.2 Topologies
• 3.3 Media Types
• 3.4 Network Devices

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Configuring a Network Interface Card
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What is a NIC?

• A network interface card (NIC) is a device that
  plugs into a motherboard and provides ports for
  the network media connections.
• It is the component that interfaces with the
  local-area network (LAN).
• The following things are important to consider
  when selecting a NIC
• The type of network
• The type of media
• The type of system bus

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Setting the IP Address

• In Windows, the IP address is manually entered
  into the TCP/IP properties dialog box.
• The configuration box is used to set the address
  settings, or configurations that are entered into
  the host machine TCP/IP dialog box, which
  include
• An IP address
• A subnet mask
• Default gateway address
• Domain Name System (DNS)
• Windows Internet Naming Service (WINS)

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DHCP Servers

• DHCP is a software utility that automatically
  assigns IP addresses to PCs.
• The computer running the software is known as a
  DHCP server.
• DHCP servers assign the IP addresses and TCP/IP
  configuration information to computers configured
  as DHCP clients.
• This dynamic process eliminates the need for
  manual IP address assignments.

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Domain Name System

• The Domain Name System (DNS) is used to translate
  the computer names such as www.cisco.com to the
  corresponding unique IP address.
• Address translations are used each time the
  Internet is accessed.
• The process of translating names to addresses is
  known as name resolution.

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Domain Name System

• The DNS server keeps records that map computer
  (host) names and their corresponding IP address.
• These record types are combined in the DNS table.
  
• When a host name needs to be translated to its IP
  address, the client contacts the DNS server.
• A hierarchy of DNS servers exists on the
  Internet with different servers maintaining DNS
  information for their own areas of authority,
  called zones.

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Default Gateway

• A computer located on one network segment that is
  trying to talk to another computer on a different
  segment sends the data through a default gateway.
  
• The default gateway is the near-side interface of
  the router.
• It is the interface on the router to which the
  local computer network segment or wire is
  attached.

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Topologies
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The Network Topology

• The network topology defines the layout of the
  network.
• It shows how devices on the network are
  interconnected.
• Devices on the network are termed nodes.
• A network has both a physical and a logical
  topology.

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Physical versus Logical Topology

• Physical topology shows the physical topology of
  a network, which refers to the actual physical
  layout of the devices and media.

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Physical versus Logical Topology

• Logical topology refers to the paths that signals
  travel from one point on the network to another.
• These two terminologies can be confusing, because
  the word "logical" in this instance has nothing
  to do with the way the network appears to be
  functioning.

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Identifying Network Topologies

• Bus Topology
• Commonly referred to as a linear bus, all the
  devices on a bus topology are connected by one
  single cable, which proceeds from one computer to
  the next.
• This topology is rarely used and would only be
  suitable for a home office or small business with
  only a few hosts.

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Identifying Network Topologies

• Advantages of a bus topology
• The thinnet cabling it uses is quite inexpensive.
  
• It uses less cable compared to other physical
  topologies like star or extended star
• It works well for small networks
• It does not need a central device, such as a hub,
  switch, or router
• Disadvantages of a bus topology
• It results in slower access to the network and
  less bandwidth due to the sharing of the same
  cable by all devices
• It is challenging to identify and isolate
  problems
• A break at any point in the bus cable can disable
  the entire bus network
• It needs terminators

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Identifying Network Topologies

• Star Topology
• The star topology is the most commonly used
  architecture in Ethernet LANs and resembles
  spokes in a bicycle wheel.
• A star topology generally costs more to implement
  than the bus topology because more cable is used
  and a central device is needed, such as a hub,
  switch, or router.

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Identifying Network Topologies

• Advantages of a Star Topology
• It is upgradeable, flexible, and reliable
• It is easy to design and install
• This topology makes diagnosing problems
  relatively easy since the problem is localized to
  one computer or device
• This topology allows for more throughput than any
  other topology
• Disadvantages of a Star Topology
• It requires a lot of cable to connect computers
  since a cable is required between each device and
  the central location.
• It is more expensive to build because of the
  additional cost of cables and devices like hubs
  and switches that are needed to run between the
  central device and each computer

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Identifying Network Topologies

• Ring Topology
• A frame, called a token, travels around the ring
  and stops at each node.
• If a node wants to transmit data, it adds that
  data and the addressing information to the frame.
  
• The frame continues around the ring until it
  finds the destination node, which takes the data
  out of the frame.
• The advantage of using this method is that there
  are no collisions of data packets.

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Identifying Network Topologies

• Ring Topology
• With single ring all the devices on the network
  share a single cable, and the data travels in one
  direction only.
• With dual ring two rings allow data to be sent in
  both directions.
• This creates redundancy (fault tolerance),
  meaning that in the event of a failure of one
  ring, data will still be transmitted on the other
  ring.
• The 802.5 standard is the Token Ring access
  method that is used.
• FDDI uses light instead of electricity to
  transmit data over a dual ring.

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Identifying Network Topologies

• The mesh topology connects all devices (nodes) to
  each other for redundancy and fault tolerance.
• It is used in wide-area networks (WANs) to
  interconnect LANs and for critical networks.
• The mesh topology is expensive and difficult to
  implement.

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Identifying Network Topologies

• The hybrid topology combines more than one type
  of topology.
• When a bus line joins two hubs of different
  topologies, the configuration is called a star
  bus.
• The bus line is used to transfer the data between
  the star topologies.

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Media Types
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Networking Media

• Networking media can be defined simply as the
  means by which signals (data) are sent from one
  computer to another.
• This includes cable or wireless means.
• There are a wide variety of networking media in
  the marketplace.

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Twisted-Pair cable

• Twisted-pair is a type of cabling that is used
  for telephone communications and most modern
  Ethernet networks.
• A pair of wires forms a circuit that can transmit
  data.
• The pairs are twisted to prevent cross talk.
• Pairs of copper wires that are encased in
  color-coded plastic insulation are twisted
  together.

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Twisted-Pair cable

• Shielded twisted-pair (STP) cable combines the
  techniques of cancellation and twisting of wires
  with shielding.
• Each pair of wires is wrapped in metallic foil to
  further shield the wires from noise.
• The four pairs of wires are then wrapped in an
  overall metallic braid or foil.
• STP reduces electrical noise from cable
  (crosstalk) and from outside the cable (EMI and
  RFI).

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Twisted-Pair cable

• Unshielded twisted-pair (UTP) has two or four
  pairs of wires.
• It relies solely on the cancellation effect
  produced by the twisted wire pairs to limit
  signal degradation caused by electromagnetic
  interference (EMI) and radio frequency
  interference (RFI).
• UTP is the most commonly used cabling in Ethernet
  networks.

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Fiber-Optic Cable

• Fiber-optic cable is a networking medium that is
  capable of conducting modulated light
  transmissions.
• To modulate light is to manipulate it so that it
  travels in the way that it transmits data.
• It refers to cabling that has a core of glass or
  plastic (instead of copper), through which light
  pulses carry signals.

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Wireless

• Wireless networks use radio frequency (RF),
  laser, infrared (IR), and satellite/microwaves to
  carry signals from one computer to another
  without a permanent cable connection.
• Wireless signals are electromagnetic waves that
  travel through the air.
• No physical medium is necessary for wireless
  signals.
• Mobile phones are a common application of
  wireless.

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Devices
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Hubs and Repeaters

• Typical LAN devices include repeaters, hubs,
  bridges, switches, and routers.
• A repeater receives the signal, regenerates it,
  and passes it on.
• Repeaters are used mainly at the edges of
  networks to extend the wire so more workstations
  can be added.

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Hubs and Repeaters

• Using a hub changes the network topology from a
  linear bus, where each device plugs directly into
  the wire, to a star.
• Data arriving over the cables to a hub port is
  electrically repeated on all the other ports
  connected to the same Ethernet LAN, except for
  the port on which the data was received.
• Hubs come in three basic types
• Passive
• Active
• Intelligent

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Bridges and Switches

• Bridges and switches operate at the data link
  layer of the OSI model.
• The function of the bridge is to make intelligent
  decisions about whether or not to pass signals on
  to the next segment of a network.
• When a bridge sees a frame on the network, it
  looks at the destination MAC address and compares
  it to the forwarding table to determine whether
  to filter, flood, or copy the frame onto another
  segment.

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Bridges and Switches

• Switches learn certain information about the data
  packets that they receive from computers on the
  network.
• They use this to build forwarding tables to
  determine the destination of data being sent by
  one computer to another on the network.
• They help segment a network and reduce network
  traffic congestion by limiting each port to its
  own collision domain.

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Routers

• Routers operate at the Network layer of the OSI
  model.
• They are slower than bridges and switches but
  make "smart" decisions on how to route packets
  received on one port to a network on another
  port.
• Routers are capable of segmenting the network.
• Routers are capable of segmenting a network into
  multiple collision domains as well as into
  multiple broadcast domains.

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Routers

• Routers can be computers with special network
  software installed on them or they can be other
  devices built by network equipment manufacturers.
  
• Routers contain tables of network addresses along
  with optimal destination routes to other
  networks.