2 Basic Concepts: data and computer networking

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2 Basic Concepts data and computer networking

• Line Configuration
• Topology
• Transmission Mode
• Categories of Networks
• Internetworks

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2.1 LINE CONFIGURATION

• Defines the attachment of communication devices
  to a link
• Two categories
• Point-to-Point
• Multipoint

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Point-to-Point Line Configuration

• Dedicated link with entire capacity of the
  channel reserved for communication
• Examples
• PC to PC (workstation)
• Mainframe to PC (Workstation)
• Satellite links

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Multipoint Line Configuration

• Multidrop
• Sharing a single link
• Spatially
• Time sharing

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2.2 TOPOLOGY

• Logical or physical layout of a network
• Two or more links form a topology
• Five Basic Topologies
• Mesh, Star, Tree, Bus, Ring

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2.2 TOPOLOGY (continue)

• Relationships among devices
• Peer-to-Peer
• Share communication link equally
• Primary-Secondary
• Master traffic controller
• Ethernet Hub

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Mesh Topology

• Every device has a dedicated point-to-point link
  to other device
• A fully connected mesh network
• n(n-1)/2 physical channels to link to n devices
• n-1 I/O ports

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Mesh Topology (continue)

• Example 1 three nodes or computers
• Number of links n(n-1)/2 3
• Number of ports n-1 2

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Mesh Topology (continue)

• Example 2 Four nodes or computers
• Number of links n(n-1)/2 6
• Number of ports n-1 3

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Mesh Topology (continue)

• Implementation usually implemented in a limited
  fashion -- a backbone connecting the main
  computers of a hybrid network
• Example ARPARNET

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Mesh Technology

• Advantages
• Dedicated point-to-point links (eliminating
  traffic problems)
• Robust (high reliability, traffic can be routed)
• Privacy or security (communications only between
  sender and receiver)
• Easy fault identification and fault isolation

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Mesh Technology

• Disadvantages
• High cost (amount of cabling and number I/O
  ports)
• Difficult to install and reconfigure

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Example 3

• 8 devices
• Mesh topology
• I/O port and links calculation
• Answer
• Number of links n(n-1)/2 8(8-1)/2 28
• Number of ports per device n-1 8-1 7

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Star Topology

• Hub (central controller) acts as a exchange
  controller which relays the data to other
  connected devices
• Each device has a dedicated point-to-point link
  only to a central controller

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Star Topology

• Advantages
• Less expensive than a mesh topology
• Robust (high reliability) if one link fails, all
  other links remain active
• Easy fault identification and fault isolation
  through central hub
• Disadvantages
• Require more cabling than in tree, ring or bus
  topology (far less cable than a mesh)

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Tree Topology

• A variation of star
• Nodes in a tree are linked to a central hub that
  controls the traffic to the network

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Tree Topology

• Secondary hubs
• For connecting devices
• Active or passive
• Central hub
• An active hub
• Repeater (enhance signals for transmitting over a
  longer distance)

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Tree Topology (continue)

• Advantages (same as star topology)
• Same advantages as star topology
• Allow more devices to be attached to a single
  central hub
• Allow the network to isolate and prioritize
  communications from different computers
• Disadvantages (same as star topology)
• Require more cabling than bus or ring topology

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Bus Topology

• Multipoint configuration one long cable acts as
  a backbone to link all the devices in the network
• Computers are connected to the bus cable by drop
  lines and taps

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Bus Topology (continue)

• Advantages
• Ease of installation
• Less cabling than mesh, star, or tree topologies
• Disadvantages
• Difficult reconfiguration and fault isolation
• Less Robust (a fault or break in the bus cable
  stops all transmission)

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Ring Topology

• Dedicated point-to-point line configuration only
  with the two devices on either side of it
• Repeaters
• A signal is passed along the ring in one
  direction from device to device, until it reaches
  its destination

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Ring Topology (continue)

• Advantages
• Relatively easy to install and reconfigure
  (maximum ring length and number of devices)
• Easy fault isolation
• Disadvantages
• Unidirectional traffic
• A break in the ring can disable the entire
  network (use dual ring or a switch)

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Hybrid Topologies

• A Combination of various topologies
• Star (hub)
• Ring
• Bus

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2.3 Transmission Mode

• Three modes
• Simplex one direction, either as transmitter or
  receiver
• Half-duplex both direction can transmit or
  receive, but one at a time
• Full-duplex can transmit and receive
  simultaneously

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Transmission Media

• Coaxial cable CATV, cable modem
• Shield twisted pair
• Un-shield twisted pair (UTP) category 5 -- up to
  100 MHz
• Optical fiber
• Wireless microwave, satellite, radio, infrared

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2.4 Categories of networks

• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)
• Long distance transmission of data, voice, image,
  and video information
• Enterprise network (owned by a single company)

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Local Area Network (LAN)

• Privately owned links and computers in a single
  office, building, or campus
• Bus, Ring, and Star topologies Topologies bus,
  ring, star, wireless, infrared
• Data rates 2 Mbps, , 10 Mbps, 100 Mbps, Gigabits

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Metropolitan Area Network (MAN)

• City wide coverage
• LAN-to-LAN
• LAN-to-other larger network

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Wide Area Network (WAN)

• Long distance transmission of data, voice, image,
  and video information
• Enterprise network (owned by a single company)
• Technologies
• ATM (Asynchronous Transfer Mode)
• Frame Relaying
• X.25 (Packet switching network)
• Circuit switching

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2.5 Internetworks

• IBM Dictionary of Computing defines
  internetworking as communications between two or
  more networks
• Two or more connected dissimilar networks
• Ethernet, Token Ring
• Dial-up lines to ISDN (Integrated Services
  Digital Network)
• ATM

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2.5 Internetworks (continue)

• Internet (World Wide Web
• Router
• Gateways