Networking

Networking

A network is a collection of connected computers plus their peripherals
1. Each device on a network is called a node
LAN
1. A LAN is confined to one site, connected using equipment owned by the organisation, and maintained by the organisation (or it may be outsourced)
2. Advantages: Central data storage makes data sharing possible and convenient, and backups easier to do, computers are easily updated or reconfigured centrally, they can easily be monitored, security policies can be centrally administered, users can communicate with each other, expensive peripherals can be shared
3. Drawbacks: maintenance incurs ban expense; specialist staff may be needed, network problems might affect all users, security may be a problem because data is accessible from many places
WAN
1. Wide area network which covers a large geographical area
2. Often connect LANs together, they make use of publicly available telecoms facilities, they allow a business to functions, allow a business to function from any location
Hardware
1. Network interface controller
  1. Each device on a network needs an NIC (LAN adapter) which are usually built into the motherboard
  2. Every NIC has a MAC address stored in ROM so each node can be identified
2. Cables
  1. Connenctions between most devices on LANs are made with copper cable (normally UTP (unshielded twisted pair) which is light, flexible and easy to install)
  2. Fibre-optic cable is used for longer distances and use outside (transmits by light waves)
3. Hubs
  1. Devices that connect many network devices together making them into a single network segment (a defined part of a network)
  2. Have a number of input and output ports and a signal arriving at one end is transmitted to all others
4. Switches
  1. Connect and act as bridges so networks can function as one (different from hub as only transmits message to intended device)
5. Wireless access point
  1. Allows LAN connections without the need for physical cables using WiFi
    1. Often connected to a router so can save money because cable is not needed
      1. Security risks can be dealt with encryption, hiding broadcast identities and allowing access to only certain MAC addresses
6. Routers
  1. It receives data in the form of packets and forwards them (often to another router
    1. They direct traffic through large networks, notably the internet
      1. Small routers in the home connect computers to teh Internet Service Provider
Types
1. Client-server network
  1. One or more servers provide services to many client machines where the user works
  2. Servers are computers that are set up to handle network functions (high-end computers with enough storage and speed), can be virtual where one physical machine can take on more than one servers functions
  3. Typical servers include: database server, file server, mail server, print server, web server, gaming server
  4. Advantage is that machines are dedicated (immediate needs) so it's efficient and high speed
2. Peer-to-peer
  1. All computers are equal - each node serves the needs of the user as well as the network function
  2. Easy to set up but maintenance is more difficult, security is poor and tend to be slow because of multitasking
  3. Useful on the internet where files can be shared directly between users without the need to go through web servers
Topologies
1. Bus
  1. The computers and other devices are attached to a single backbone
    1. A terminator prevents reflection of signals which travel in either direction
  2. Plus: easy to set up, cheap
  3. Negative: problems with backbone can bring the whole network down, limited distance covered, many data collisions slow the network down
2. Star
  1. Client machines are connected to a central switch or hub, which is usually connected to one or more servers (signals either direction)
  2. Plus: robust (problems don't affect the whole network), fewer data collision than bus so faster
  3. Negative: needs expertise, can be expensive because more building work involved and more network hardware and software needed
3. Ring
  1. Data passes through each node, carried in data units called tokens
  2. Plus: very fast - no collisions
  3. Negative: problems in backbone can bring whole network down and data passes through every node so makes network vulnerable to malfunctions

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