1.3.2 Networks

1.3.2 Networks

1. What is a network?

   • ‘Networks are collections of connected computing devices. They consist of a number of devices known as nodes, which are mostly computers of various kinds but also shared peripherals such as printers, scanners and secondary storage devices’ (OCR, 2015).
   • Allow data to be shared between nodes

2. Private Networks

   • Advantages
     • Control over security
     • Complete control over who has access to what resources
     • Control over what software is provided
     • Confidence of availability
     • The ability to restrict the use of executable files
   • Disadvantages
     • Specialist networking staff are required on site around the clock to maintain the network and correct any errors that occur
     • Dependency on the network is disastrous if theres an outage. It brings holistic service to a halt, people are left unable to do their jobs. To prevent this, precautions need to be taken:
       • Duplicates of essential equipment might be kept
       • Regular, well thought out backups might be kept
       • Fail-safe systems, UPS etc

3. Topolgy

   • Bus topolgy
     • Nodes are attached to a common backbone, typically based on copper wire and is limited in its potential physical size. The longer the bus, the weaker the signal becomes.
       • If this backbone fails, the entire network is lost
     • One common linking communications cable (bus)
     • Nodes connected off the cable
     • Cheap
     • Slows down when heavy traffic
     • Lots of data collisions
     • Breakage to bus will affect whole network
     • Limited distance covered
   • Ring Topology
     • Nodes connected in a ring, data passed in single direction around ring (with view to preventing data collisions). Each node is connected to exactly two other nodes
     • One common linking cable
     • Passes through NIC of each node
     • One direction traffic
     • Fast performance
   • Star Topology
     • Central hub or switch links the nodes, commonly connecting the nodes to a server or multiple servers. It’s the most common type of network topology in modern day as its easy to add or remove devices
     • Shared link to server(s)
     • Central node is the Hub
     • Hub has separate connections to each node
     • Fast, robust & cost effective
     • Few data collisions
     • Can set up independent segments
     • Hub can be another node, or switch etc