Computer Applications Technology

• Bus topology


  A network type in which every computer and network device is connected to a single cable

  
• Linear Bus topology


  • Bus topology with exactly two endpoints
• Features of Bus Topology


  • Transmits data only in one direction
  • Every device is connected to a single cable

  
• Advantages of Bus Topology


  • Cost effective
  • Least cable required compared to other topologies
  • Used in small networks
  • Easy to understand
  • Easy to expand by joining two cables
• Disadvantages of Bus Topology


  • Whole network fails if cable fails
  • Performance decreases with heavy traffic or more nodes
  • Cable has limited length
  • Slower than ring topology
• Mesh topology


  A point-to-point connection to other nodes or devices, where all network nodes are connected to each other

  
• Mesh has n(n-1)/2 physical channels to link n devices
• Techniques to transmit data over Mesh topology


  • Routing
  • Flooding

  
• Routing in Mesh topology


  Nodes have routing logic to direct data to destination using shortest distance, avoid broken links, and reconfigure failed nodes

  
• Flooding in Mesh topology


  Same data is transmitted to all network nodes, no routing logic required, robust but leads to network load

  
• Types of Mesh Topology


  • Partial Mesh (some devices only connected to 2-3 others)
  • Full Mesh (each node connected to every other node)
• Features of Mesh Topology


  • Fully connected
  • Robust
  • Not flexible
• Advantages of Mesh Topology


  • Each connection can carry its own data load
  • Robust
  • Fault is diagnosed easily
  • Provides security and privacy

  
• Disadvantages of Mesh Topology


  • Installation and configuration is difficult
  • Cabling cost is more
  • Bulk wiring is required
• Topology


  The mapping of a LAN design
• Tree topology


  Has a root node with all other nodes connected to it in a hierarchy
• Features of Tree Topology


  • Ideal if workstations are located in groups
  • Used in Wide Area Network
• Advantages of Tree Topology


  • Extension of bus and star topologies
  • Expansion of nodes is possible and easy
  • Easily managed and maintained
  • Error detection is easily done
• Disadvantages of Tree Topology


  • Heavily cabled
  • Costly
  • Maintenance is difficult with more nodes
  • Central hub failure causes network failure
• Ring topology


  Computers and devices are connected in a closed loop cable, with no terminating ends

  
• Features of Ring Topology


  • Transmission is unidirectional, but can be made bidirectional with Dual Ring Topology
  • Data is transferred sequentially, bit by bit, passing through each node

  
• Advantages of Ring Topology


  • Network not affected by high traffic or more nodes, as only nodes with tokens can transmit
  • Cheap to install and expand
• Disadvantages of Ring Topology


  • Troubleshooting is difficult
  • Adding/deleting computers disturbs network activity
  • Failure of one computer disturbs whole network
• Star topology


  All computers and devices are connected to a main hub or switch, which aggregates and distributes the data flow
• Features of Star Topology


  • Every node has dedicated connection to hub
  • Hub acts as a repeater for data flow
  • Can use twisted pair, optical fibre or coaxial cable
• Advantages of Star Topology


  • Fast performance with few nodes and low traffic
  • Hub can be upgraded easily
  • Easy to troubleshoot
  • Easy to setup and modify
  • Only affected node fails, rest work smoothly
• Disadvantages of Star Topology


  • Cost of installation is high
  • Expensive to use
  • If hub fails, whole network stops
  • Performance depends on hub capacity
• Hybrid topology


  A combination of two or more different network topologies
• Features of Hybrid Topology


  • Combination of two or more topologies
  • Inherits advantages and disadvantages of included topologies
• Advantages of Hybrid Topology


  • Reliable with easy error detection and troubleshooting
  • Effective
  • Scalable with easy size increase
  • Flexible
• Disadvantages of Hybrid Topology


  • Complex in design
  • Costly
• Wide Area Network (WAN)


  A large network of computers that covers a wide area such as a city, province, country or even the world. Communication methods include cables, microwaves, radio waves and satellites.
• Purpose and role of a WAN

  • Connect LANs together
  • Facilitate communication between users over a large distance
  • Share a central data source
• The Internet


  A huge collection of LANs, servers and computers connected to each other by communication channels
• Internet services


  • Instant messaging
  • Voice over Internet protocol
  • File sharing
  • Grid/cloud computing
• File Transfer Protocol (FTP)


  Sets the rules for the way in which files will be transferred or exchanged over the Internet. This includes uploading and downloading files.
• Cloud computing


  Lets you make use of storage and applications facilities that are not necessarily hosted on your computer. Data and applications can be accessed from any computer connected to the Internet.
• Grid computing


  The use of multiple computer systems as one. Allows processes to happen over the multiple systems that will not be able to happen on one computer system, saving money.
• Examples of cloud computing


  • Google Docs
  • iCloud
• File sharing


  Data is stored on servers around the world using the Internet to transfer files.