Chapter 2

• Computer networking


  Interconnected computing devices that can exchange data and share resources with each other
• Main benefits of networking computers and devices

  • Devices, such as printers, can be shared (thus reducing costs)
  • Licenses to run software on networks are often far cheaper than buying licences for an equivalent number of stand-alone computers
  • Users can share files and data
  • Access to reliable data that comes from a central source, such as a file server
  • Data and files can be backed up centrally at the end of each day
  • Users can communicate using email and instant messaging
  • A network manager can oversee the network and, for example, apply access rights to certain files, or restrict access to external networks, such as the internet
• Drawbacks of networking computers and devices

  • Cabling and servers can be an expensive initial outlay
  • Managing a large network can be a complex and difficult task
  • A breakdown of devices, such as the file servers, can affect the whole network
  • Malware and hacking can affect entire networks (particularly if a LAN is part of a much larger WAN), although firewalls do afford some protection in this respect
• Private networks


  Owned by a single company or organisation, often LANs or intranets with restricted user access
• Public networks


  Owned by a communications carrier company, many organisations will use the network and there are usually no specific password requirements to enter the network
• Common types of enterprise private networks

  • Local area networks (LANs)
  • Wireless LANs (WLANs)
  • Wide area networks (WANs)
  • Metropolitan area network (MANs)
• Local area networks (LANs)


  Network covering a small area such as a single building, consisting of a number of computers and devices connected to hubs or switches
• Wireless LANs (WLANs)


  Similar to LANs but with no wires or cables, providing wireless network communications over short distances using radio or infrared signals
• Wide area networks (WANs)


  Network covering a very large geographical area, used when computers or networks are situated a long distance from each other
• Metropolitan area network (MAN)

  Network which is larger than a LAN but smaller than a WAN, covering several buildings in a single city
• Client-server model


  Uses separate dedicated servers and specific client workstations, with the server dictating which users can access which files
• Peer-to-peer networking

  This is communication with other peers who connected together on the internet. They are both consumers and suppliers of information.

  
  

  One computer is used to find which laptops have particular services. Used in small businesses
• Thin client

  Heavily dependent on having access to a server to allow constant access to files and to allow applications to run uninterrupted
• Thick client

  Can work offline or online, capable of operating effectively whether connected to a server or not
• Network topologies


  • Bus networks
  • Star networks
  • Mesh networks
  • Hybrid networks
• Bus network


  Uses a single central cable to which all computers and devices are connected, with data only able to travel in one direction
• Star network


  Uses a central hub/switch, with each computer/device having its own dedicated connection to the central node
• Mesh network


  Two types: routing (nodes have routing logic to direct data by the shortest route) and flooding (sends data via all nodes with no routing logic)
• Hybrid network


  A mixture of two or more different network topologies
• Public cloud


  Storage environment where the customer/client and cloud storage provider are different companies
• Private cloud


  Storage provided by a dedicated environment behind a company firewall, with customer/client and cloud storage provider integrated
• Hybrid cloud


  Combination of private and public clouds, with some data in private cloud and less sensitive/commercial data in public cloud
• Companies transferring confidential data to cloud storage are relinquishing control of their own data security
• Wi-Fi and Bluetooth


  Both offer wireless communication between devices using electromagnetic radiation as the carrier of data transmission
• Bluetooth


  Sends and receives radio waves in a band of 79 different frequencies centred on 2.45 GHz, with devices automatically detecting and connecting to each other using spread spectrum frequency hopping
• codes to access confidential data for monetary purposes?
• S Mathanki UNIT 1- Topic 2 Networking Computer Science 9618
• Types of networking


  • Wired
  • Wireless
• Wi-Fi


  Wireless communication between devices using electromagnetic radiation as the carrier of data transmission
• Bluetooth


  Wireless communication between devices using radio waves in a band of 79 different frequencies centred on 2.45 GHz
• Bluetooth communication


  1. Devices automatically detect and connect

  2. Each communicating pair uses a different channel

  3. Device picks a random channel if the first is in use

  4. Communication pairs constantly change the frequencies they are using
• Bluetooth WPAN


  Secure wireless personal area network based on key encryption
• Bluetooth


  • Useful for transferring data between devices less than 30 metres apart
  • Suitable for low bandwidth applications
  • Data transmission speed is not critical
• Penetration


  Ability of electromagnetic radiation to pass through different media
• Attenuation


  Reduction in amplitude of a signal
• Infrared has low attenuation but is suitable for indoor use only as it can be stopped by walls
• Microwaves offer a good compromise, supporting reasonable bandwidth and having reasonable penetration and attenuation
• Curvature of the Earth prevents short-distance electromagnetic waves from transmitting data globally
• Communication between antennae and satellite is carried out by radio waves or microwave frequencies
• Types of wired cables

  • Twisted pair
  • Coaxial
  • Fibre optic