Networks

Networks

1. Networks

   • Is a set of connected computers and other devices in order to share resources
   • Advantages
     • Workgroups - Groups of users can easily send data to each other over networks
     • Shared databases - Allows different users to make and modify databases
     • Distributed systems - Possible to divide a problem into separate parts for other computers to solve, so the task can be done faster
     • Communications - Skype, email - better than letters and conferences
     • Device sharing - Jobs can be sent to devices (eg printers) from any computer
     • Software sharing and maintenance - Can update software on all computers at the same time
   • Disadvantages
     • Expertise - Building a server needs knowledge
     • Security - Can help unauthorised people get access to data

2. Network hardware

   • Network Interface Card (NIC) - Circuit that prepares and generates
   • Terminator - A device attached to the end of a bus network to prevent signals from bouncing
   • Repeaters - The signal weakens and the information it carries can be corrupted. A repeater cleans a message and sends it to the next segment of the network
   • Hubs - They are repeaters, but with more than one output port. They can boost signals and send it to all devices in the output ports
   • Bridges - They connect different network segments as well as different media. They can operate on packets and send them to the right segment. They speed up a networks performances
   • Switches - It is a high-speed bridge, it has a dedicated CPU designed to perform switching operations
   • Router - They work with data packets, a router allows data to be sent between departments or ISP's
   • Wireless access points - allows a WiFi device to connect to a wired network

3. Types of Networks

   • Peer-To-Peer
     • All computers are equal.
     • Security is up to each user
     • Often uses a hub
     • Difficult to keep track of who has what information
     • Suitable for a small office or home
   • Client Server
     • Most common network
     • Needs one computer dedicated as a server
   • Star topology
   • Ring topology
   • Bus topology

4. LAN vs WAN

   • LAN - Local area network. Located in one site. Short range.
   • WAN - Wide area network. LANs connecting to other LANs. Can be used to connect a companies LANs together even if they are in other countries

5. Terms

   • IP address - a unique string of numbers separated by full stops that identifies each computer
   • MAC address - A MAC address is given to a network adapter when it is manufactured. It is hardwired or hard-coded onto your computer's network interface card (NIC) and is unique to it
   • Packet - is a unit of data made into a single package that travels along a given network path
   • Protocols - rules used for devices to communicate

6. Security

   • People dont want data to fall into the wrong hands
   • Strong passwords are needed so they are hard to guess
   • Packets of data are encrypted so if they do fall into the wrong hands they cant be used
   • Levels of access are determined by user id - they stop unauthorised people from messing with the network

7. Network policies

   • Disasters - they happen - companies have procedures and plans with three steps - prevention, detection and correction
   • Failover - Automatic switching to a backup computer system in the event of system failure
   • Back-up - Data is copied regularly to a storage device in case some is deleted
   • Archiving - When data is no longer is used it is stored somewhere else but deleted from the primary system in case someone needs the data again

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