1_Computer Communications and Networking

1_Computer Communications and Networking

1. Why network computers?

   • Sharing resources like internet connections and printers.
   • Easier to manage multiple computers. This includes installing softwares and setting accross multiple computers remotely
   • Users no longer need to be tied t oa single computer to access their data and programs
   • internet: a globally interconnected network of computers
     • lets you do: email, voice over internet protocol (skype), upload images/downloads, gaming, security camera, light switches
   • MESH network: what the networks are all connected by, lots of star networks joining together
   • peer-to-peer networks: when individual computers have individual connections to each other. All have equal status so no servers

2. ubiquitous computing : that surrounds us and is everyone in our lives

3. Network Topology

   • mathematical study of shapes and nodes
   • The structure of the under-laying nodes and connections for a network is known as topology
   • LAN: local area network,only specific people can access it
   • WAN: Wide area network, only one person can access it
   • TYPES OF TOPOLOGY
     • Bus network
       • Has a central cable that all devices are connected to
       • Only once device at a time can access the bus at a time
       • Terminators are placed at each end of the bus network
       • east to set up and to add more nodes. also cheap to install
       • network can be slow depending on how busy it is
       • easy to fail as only reliant on 1 connection
     • Star network
       • can be added to easily
       • can be centrally managed
       • each node is independent
       • data transmission speeds can vary
       • saves cabling
       • can be vulnerable to central hub failures
       • a servicing or 'miniframe' system for control of messaging is needed to keep it safe
       • most commonly used topology
       • each device is directly connected to a central server
       • home network is a star, connecting through the wifi router
     • ring network
       • no central host computer
       • none of the nodes need overall control
       • imaginary token is (small packet of data) continuously passed around the ring
       • as token goes round, 1 node takes it and sends message to say where it is
       • uses more cabling, more expensive
       • can add more nodes
       • difficult to extend
       • only travels in 1 direction so large volumes can be sent
       • faster than a bus network
       • relies heavily on ring repeater

4. Types of Compression

   • lossless: no data is lost just stored more efficiently
   • lossy: when making smaller, removing quality and data from photo
   • keyframe: number of frames refreshed per second
   • grandfather,father,son model: a complete backup is done and then only changes are only backed up not the whole hard drive. this takes less time than a whole back up

5. Types of servers

   • types of devices that computers connect to: hubs and switches (faster, can handle more connections)
     • changing a hub to a switch means data transfer is managed more efficiently
     • a fast witch between the 2 suite switches means that data can be split between the 2 efficiently
   • web cache; type of server that hold commonly used web pages, saves network going to internet everytime
   • file server: everyone can access own files from any computer, can also have own secure space in server
     • for extra security can back up to tape
   • multimedia server: holds over several CD's at once, users can access cd's info without the physical cd each time
   • email server: manages all interval emails locally and only sends external mail to the internet
   • domain name server (DNS): named of website is looked up on one of the other servers and finds out the address of the web host

6. Web addresses

   • HTTP: Hyper Text Transfer Protocol
   • when putting in a URL, you are requesting to access a network/ web page
   • protocol; a set of rules that all devices on a network must follow if they are to be able to communicate to each other
   • each network interface has a unique media access code (MAC), these help the network to identify each device
   • domain name: going to a specific server page 'bbc'
   • IP address: like a post code for each device
   • DNS: domain name server used to find IP adress