topology

• Network

  More than one computer system connected together allowing for communication and sharing of resources
• Network types

  • Local Area Network
  • Wide Area Network
  • Client-Server Network
  • Peer-to-Peer Network
• Client-Server Network

  Clients make requests to a server, the server manages that request and responds
• Large services like Amazon and Google will need very powerful servers to handle millions of requests a second
• Client

  Completely dependent on the server to provide and manage the information
• Server

  Controls network security, backups and can be upgraded to manage higher demand
• Advantages of Client-Server Network

  • The network can be controlled centrally from the server to easily backup data and update software
  • Hardware, software and resources can be shared across the network, such as printers, applications and data files
  • The network allows for improved scalability, meaning more clients can be easily added to the central server
• Disadvantages of Client-Server Network

  • Large amounts of traffic congestion will cause the network to slow down
  • If a fault occurs with the server then the whole network will fail
  • IT technicians may be required to manage and maintain the network
  • Malware, such as viruses, can spread quickly across the network
• Peer-to-Peer Network

  Data is shared directly between systems without requiring a central server. Each computer is equally responsible for providing data.
• Advantages of Peer-to-Peer Network

  • This is a simpler network than client-server to set up as no server is required
  • Clients are not dependent on a server
  • Perfect for quickly sharing files between systems, such as downloading media files
• Disadvantages of Peer-to-Peer Network

  • Without a dedicated server there is no central device to manage security or backups. Backups must be performed on each individual system.
  • Computer performance will decrease with more devices connected to the network, especially if other machines are slow.
• Local Area Network (LAN)

  Computer systems situated geographically close together, usually within the same building or small site, like a school or office
• Wide Area Network (WAN)

  Computer systems situated geographically distant to each other, possibly across a country or even across the world
• WANs often use third party communication channels, such as connections by internet services providers like BT or Virgin Media
• Other network types

  • Metropolitan Area Network (MAN) for computer systems connected across a town or city
  • Personal Area Network (PAN) for devices connected and used by an individual
• Data Packets

  Smaller parts that files are broken down into when sending data across a network to allow for quick transfer
• Contents of a Data Packet

  • Header
  • Payload
  • Trailer
• Checksum

  Calculation on the data to see if any errors or corruption have occurred during transmission
• Network Topology

  Layout of computer systems on a local network
• Network Topology Types

  • Star
  • Mesh
• Star Topology

  Each computer system is connected to a central device, usually a hub or switch
• How Star Topology Works

  • Each computer system is connected to the central hub or switch and transfers its data packets there
  • The hub or switch looks at the destination address and transfers the packets directly to the intended computer
• Advantages of Star Topology

  • Improved security as data packets are sent directly to and from the hub/switch
  • New systems can be attached directly to the central system so the network doesn't need to be shut down
  • System failures of attached computers won't usually cause complete network failure
  • Transfer speeds are generally fast as there are minimal network collisions
• Disadvantages of Star Topology

  • Extra hardware (the hub or switch) is required to be purchased, installed and maintained
  • If the central system (the hub or switch) fails then the whole network will be unusable until the error is fixed
• Mesh Topology

  In a full mesh network, each computer system is connected to every other computer system. There is also a partial mesh network where only some nodes (e.g. a printer) are connected to every other node.
• How Mesh Topology Works

  • Data packets are transferred to the destination address along the quickest path, travelling from node to node
  • If a pathway is broken, there are many alternative paths that the packets can take
• Advantages of Mesh Topology

  • If one cable or system fails then data packets can take an alternative route and still reach the destination address
  • Because of the large possible number of systems and connections, a mesh topology can usually withstand large amounts of data traffic
  • New systems can be added to the network without disrupting the entire topology
• Disadvantages of Mesh Topology

  • Because of the possibly large amount of cables required (especially in a full mesh topology) this network layout can be expensive to install and maintain
  • Redundant cabling should be avoided - this is when cables are connected between systems that won't ever need to communicate
• Bandwidth

  The maximum amount of data that can be sent across a network at once
• Factors affecting network performance

  • Bandwidth available
  • Interference (e.g. thick walls)
  • Applications being used
  • Number of users at the same time
  • Distance to travel / signal strength
  • Server / CPU Performance
  • Number of data collisions
  • Amount of data to transfer