Computers and Networking Systems

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Computers and Networking Systems

• Class 6.1

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Chapter 11

• PCs on a Network

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You Will Learn

• How local networks are structured
• How to connect a PC to a LAN and divide a network
  into segments
• How to connect networks to each other

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Network Architecture

• Describes overall design of the network
• Physical components
• Network technologies
• Interfacing software
• Protocols needed to establish reliable
  communication among nodes

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Physical Network Architectures

• Ethernet (most popular)
• Token ring
• FDDI (Fiber Distributed Data Interface)
• Wireless LAN technology

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Network Architecture Terminology

• Network adapter
• Most often an expansion card called a network
  interface card (NIC)
• Must match type and speed of physical network in
  use
• Network port must match type of connectors used
  on the network
• Network protocols
• Hardware protocols (eg, Ethernet, Token Ring)
• OS protocols (eg, NetBEUI, TCP/IP)

continued
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Network Architecture Terminology

• Packets, datagrams, or frames
• Packets have maximum size depending on type of
  network
• CRC (cyclical redundancy check)
• Technique of calculating and comparing values

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Ethernet Variations, Distinguished by Speed

• 10-Mbps Ethernet
• Uses either shielded twisted-pair (STP) cable,
  unshielded twisted-pair (UTP) cable, or coaxial
  cable
• 100-Mbps Ethernet or Fast Ethernet
• Uses UTP or STP cable
• 100BaseFX uses fiber-optic cable (single-mode,
  multi-mode, and plastic)
• 1000-Mbps Ethernet of Gigabit Ethernet
• Uses twisted-pair and fiber-optic cable

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Cable Types Used with Ethernet
continued
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Cable Types Used with Ethernet
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Comparison of Ethernet Version Cable Types
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Ethernet Topology

• Bus topology
• Connects each node in a line
• Does not have a centralized point of connection
• Star topology
• Connects all nodes to a centralized hub
• More popular

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Ethernet Topology Bus or Star
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Ethernet Using Star Topology
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Ethernet Hub
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Ethernet UsingStar Bus Topology
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Ethernet Network

• A passive network
• Contention-based system
• Each computer contends for an opportunity to
  transmit on the network
• Requires collision control

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How Ethernet ControlsData Traffic

• CSMA/CD (Carrier Sense Multiple Access with
  Collision Detection)
• CSMA/CA (Carrier Sense Multiple Access with
  Collision Avoidance)
• Token method

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Repeaters
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Token Ring

• Physical star logical ring
• Data packet is preceded by a token
• Transmits data at 4 Mbps or 16 Mbps
• Uses a centralized device called a MAU
  (Multistation Access Unit)

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Token Ring
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FDDI

• Use a token that travels in a ring
• Data frames travel on the ring without the token
• Multiple nodes can have data on the ring at the
  same time
• Provides data transfer at 100 Mbps

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Wireless LANs (WLANs)

• Make connections using wireless NICs
• Include antennas or infrared transmission to send
  and receive signals in places where networking
  cables are difficult to install
• Can be used in combination with a wired LAN
• Standards
• 1999 IEEE 802.11b (Wi-Fi, AirPort)
• Bluetooth
• Slower than wired networks
• Security is an issue

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WLANs
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Connecting a PC to a Network

• Requirements
• NIC
• Network cable (patch cable)
• Device for PC to connect to (eg, hub)
• How NICs work and how to install them
• How to set up a network protocol
• Using bridges and switches to divide a network
  into segments for improved performance

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How NICs Work

• Plug into motherboard expansion slot
• Provide port(s) on back of card for connection to
  network
• Manage communication and hardware network
  protocol for the PC

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An Ethernet Network Card
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How NICs Work

• Network in use is transparent to applications
  software using it
• Network card
• Sends and receives data to and from system bus in
  parallel
• Sends and receives data to and from network in
  series
• Uses a transceiver for signal conversion
• Network nodes are identified by a MAC (Media
  Access Control) address

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Symptoms of NIC Problems

• Cannot make connection to network
• Network Neighborhood or My Network Places does
  not show any other computers on the network
• Error message during installation
• Device Manager shows yellow exclamation point or
  red X beside name of NIC
• No lights on NIC

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Troubleshooting a Network Connection

• Check connections in rest of network
• Reboot PC and reset network connections
• Make sure NIC and its drivers are installed
• For TCP/IP network, use ping 127.0.0.1 command to
  determine whether NIC and IP protocol are working
• Check for an IRQ conflict
• Check cabling and ports
• Confirm most current version of motherboard BIOS

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Segmenting a Network

• Decreases amount of traffic on overall network
• Done through use of bridges and switches
• More intelligent than hubs
• Make decisions about whether or not to allow
  traffic to pass, or where to forward that traffic
• Use MAC addresses, which they store in routing
  tables, to determine where to send packets

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Bridges
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Bridges
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Bridges and Switches

• Bridges
• Send broadcast messages do not work well with
  large networks
• Effective at separating high-volume areas on a
  LAN
• Work best when used to connect LANs that usually
  do not communicate outside their immediate
  network
• Switches
• Send a packet only to network segment for which
  it is destined

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Bridges Compared with Switches
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Connecting Networks

• Communication between networks uses TCP/IP (not
  MAC addresses)
• Methods of network connection
• Routers
• Bandwidth technologies

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Routers

• Use IP addresses to determine path by which to
  send a packet
• More efficient than switches in choosing routes
  for packets over long distances
• Stateless devices
• Unconcerned about data concerned about
  destination address of data

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Using Routers to Connect Networks
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Networking Protocols

• A router can transmit a data packet to a remote
  network only if a routable protocol
• Was used to produce the data packet
• Can be routed to a remote network
• Routable
• TCP/IP
• IPX/SPX
• Not routable
• NetBEUI

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Brouter

• Functions both as a bridge and a router
• As a router
• Can route routable protocols (TCP/IP and IPX/SPX
  packets)
• As a bridge
• Forwards packets that are not routable (NetBEUI
  packets) to other local networks

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Bandwidth

• Measures how much data can travel over a given
  communication system in a given amount of time
• Also called data throughput or line speed
• Greater bandwidth faster communication

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Bandwidth Technologies
continued
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Bandwidth Technologies
continued
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Bandwidth Technologies
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Common Bandwidth Technologies

• Regular telephone lines
• Cable modem
• ISDN (Integrated Services Digital Network)
• DSL (Digital Subscriber Line)
• Satellite access
• Wireless access

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Chapter Summary

• How local networks are built
• How bridges and switches can segment large local
  networks
• How routers connect networks
• Technologies used to connect PCs and networks to
  the Internet
• Servicing PCs that are connected to a network