chapter 2

• Networking devices


  Interconnected devices that allow a fast means of data transmission within the network
• Networking benefits


  • File sharing
  • Resource sharing
  • Higher storage
• LAN (Local Area Network)


  Network that connects devices within a small geographical area
• WAN (Wide Area Network)


  Network that connects devices within a larger geographical area
• Differences between LAN and WAN

  • Only private ownership (LAN)
  • Private or public ownership (WAN)
  • Transmission medium: twisted pair cable, coaxial cable or Wi-Fi (LAN)
  • Transmission medium: PSTN or satellite link (WAN)
  • Higher data transfer rate (LAN)
  • Lower data transfer rate (WAN)
  • Lesser congestion (LAN)
  • Higher congestion (WAN)
• Client-server model


  Server based network: dedicated server provides an application (administration of users, security and resources) for the client computer to utilize
• Client-server applications


  • Printer
  • File Sharing
  • Proxy server
  • Email server
  • Database server
  • Domain controller server
• Management of user accounts

  Client sends login request to server which processes and grants request if user ID & password recognized
• Thin Clients


  A client that solely runs on the resources provided by the server and has no local storage
• Thick Clients


  An independent client that does not require the server to run
• Peer-to-peer network model (P2P)


  Decentralised network where each connected computer stores data and operates independently as a 'peer', and can act as both a client & server
• Applications of P2P


  • Internet
  • Ad hoc networks
• Differences between Client-server and Peer-to-peer models

  • Centralized backup (Client-server)
  • Lesser initial setup cost (P2P)
  • Files & resources centralized in server: prevents illegal resource usage (Client-server)
  • Lesser network traffic: each peer can simultaneously receive data from different sources (P2P)
  • Improved security: files are stored on central server which would be regularly scanned for malware (Client-server)
  • Can work even if a device goes down, but Client-server model can't work if server goes down (P2P)
• Bus topology


  Single line (bus) connecting all devices with terminators at each end
• Star topology


  Consists of a central server ('Switch') and all other computers connected with a dedicated connection to each, hence server can send packets to different devices simultaneously and bi-directionally
• Mesh topology


  Network setup where every device (node) is directly interconnected to the each of the other devices (nodes)
• Hybrid topology


  Combination of two or more topologies
• Benefits of wired networks

  • Less expensive and easier to install (Copper Cable)
  • Greater bandwidth, Improved security, Lightweight: easy to install, Less signal boosting required; used in long distance comm. (Fiber-Optic Cables)
• Drawbacks of wired networks

  • Doesn't perform well with small charges, Affected by electromagnetism (Copper Cable)
  • Needs expensive optical transmitters and receivers (Fiber-Optic Cables)
• Benefits of wireless networks

  • Can travel over large distances since they have largest range of wavelength, Relatively inexpensive (Radio waves)
  • Larger bandwidth, can transfer more data at a time (Micro-waves)
  • Cheap with long distance, Used for Satellite phones, satellite radio broadcast (Satellites)
• Drawbacks of wireless networks

  • Low frequency so transmits less data at one time, Affected by radio stations with similar frequency (Radio waves)
  • Emitting towers expensive to build, Physical obstacles can interfere (Micro-waves)
  • Easy to interfere, Expensive set up (Satellites)
• Ethernet


  Most common wired medium of transmission, that can be used to transfer data between LANs or WANs
• CSMA/CD (Carrier Sense Multiple Access Collision Detection)


  1. Before transmitting, device checks if channel is busy

  2. If busy, device calculates a random wait time and waits that time, after which it begins transmission

  3. Then during transmission, the device listens for other devices also beginning transmission

  4. If collision, transmission is aborted and both devices wait different random times, then try again
• Bit Streaming


  Sequence of digital signals (bits) transferred over a communication path at high speeds
• Methods of bit streaming

  • Real-time
  • On-demand
• Real-time bit streaming


  Event captured live via video camera that is connected to a computer, Video signal converted to an encoded streaming video signal, Encoded video signal uploaded from computer to a dedicated streaming server via cables or high-speed wireless internet connection, Server then sends live images to all users requesting it as a real-time video, Cannot be paused, fast-forwarded, etc.
• On-demand bit streaming


  Existing digital files converted to encoded bit-streaming format for broadcasting on the internet by uploading to a dedicated server, A link for encoded video is placed on website and the user clicks on link to view encoded streaming video, The data is streamed to a buffer in user's computer and the buffer stops the video from being paused as the bits are streamed, Can be paused, fast-forwarded, etc.
• Importance of high broadband speed / bit-rate: User has to download and display bits at same time, If media is of higher quality, then higher broadband speed needed since each "frame" is of a larger size, Real-time needs faster broadband speeds as compared to on-demand, since there are a greater number of users simultaneously requesting same data
• Cloud Computing


  Refers to the on-demand provision of computing services through the internet
• Services provided by cloud computing

  • Infrastructure: Storage capacity and higher processing power
  • Platform: Software, testing & debugging resources
• Public cloud


  3rd-party cloud service provider grants access to multiple parties, accessible via a browser
• Private cloud


  A private cloud is owned by one organization and is not shared with any other organization
• Benefits of cloud computing

  • Relatively less technical knowledge required and easy to implement
  • Flexibility: Cloud Can Be Scaled To Match The Organization's Growth
• Drawbacks of cloud computing

  • Cannot access the resources/data stored on the cloud, if there are bandwidth issues
  • Poor data privacy, since there may be data leakage in the multi-tenant architecture (public clouds)
• World Wide Web (WWW)


  Collection of web pages stored on websites
• Internet


  Massive, open network of networks, Uses TCP/IP protocol, which uses IP addresses to identify devices connected to the internet, Access provided by Internet Service Provider, Communication used: wired, radio and satellite
• Router


  Connects two networks together which operates under the same protocols, Allows internal connections between LANs OR allows external connection from the main LAN to a WAN, The router acts as a gateway & firewall, Usually, it will be attached to a server or switch in a LAN, The router translates private IP addresses to public IP addresses AND vice versa
• LAN-supporting hardware


  • Switch
  • Server
  • Network Interface Card (NIC)
  • Wireless Network Interface Card (WNIC)
  • Wireless Access Points (WAP)
  • Cables
• Bridge


  Connects two LANs which work use the same protocol, which can be two segments of the same network, Stores network addresses for all devices (end-systems) between the 2 networks, A bridge looks for the receiving device before it sends the message
• Repeater


  Connects two cables, regenerates the sent data signal over the same network before the signal weakens (attenuation) to prevent it from being corrupted