Networks (except Packets and Protocols)

Networks (except Packets and Protocols)

1. Topologies

   • Bus
     • All systems (nodes) are attached to a single cable on which data can be sent, called the backbone. All communication must be transferred through this.
       • It has terminators on each end, which are needed to ensure that the network functions correctly.
     • Advantages
       • Easy to implement and add more computer systems to the network.
       • Quick to set up - well suited for temporary networks.
       • Cost-effective - less cabling
     • Disadvantages
       • Difficult to troubleshoot
       • Limited cable length and number of stations - performance degrades as additional nodes are added
       • If there is a problem with the backbone or connection, the entire network goes down
       • Data collisions are more likely, which causes the network to slow down.
   • Ring
     • Nodes are connected in a ring/loop.
       • Around the ring, packets are sent, being passed from one node to the next until they arrive at their destination.
     • Advantages
       • Very high rates of transmission - no bottleneck of data
       • No network collisions as only one batch of data is allowed at any one time
       • Adding additional nodes has very little impact on bandwidth
     • Disadvantages
       • Failure of a single cable or device can bring down the entire network
       • Security is not ensured, as data passes through other devices en route to its final destination
       • Difficult to troubleshoot
   • Star
     • All nodes are connected to a central device, like a switch or hub.
       • Communication must go via this central device.
     • Advantages
       • Fast network speed
       • Faults are easy to find
       • Better security
       • Any non-centralised failure will have very little effect on the network
     • Disadvantages
       • Expensive to install - more cabling required
       • Extra hardware required, such as a hub

2. A network is a collection of computers and other hardware that has been connected together in order to allow the communication and sharing of resources.

   • They also allow software to be installed and controlled across the network from a single computer rather than individually on every machine, saving time.

3. Types of network

   • Local Area Network (LAN)
     • All computer systems are located relatively close to each other.
   • Wide Area Network (WAN)
     • All computer systems are located relatively distant from each other

4. Hardware

   • Router
     • Allows communication between a LAN and the Internet
   • Hub
     • A device to which lots of computers can be connected to so they can communicate, usually with Ethernet cables
   • Switch
     • Performs the same job as a hub, but learns the locations of the computers and other devices plugged into it.
       • This makes the network more efficient as far fewer unnecessary signals travel down the wrong cables.
   • Network Interface Card (NIC)
     • Needed for a computer to be added to a network.
     • Where an Ethernet cable would be plugged in, or where the wireless signal would be received.

5. User access levels

   • Depending on who you are, you will have certain privileges within a network.
     • These are advantageous as they prevent unauthorized people from changing parts of the system that would affect other users, and helps prevent hackers from gaining access to sensitive information.

6. Network policies

   • Acceptable use
     • Sets out what users are permitted to do and are not permitted to do within a network.
     • Without employees signing this, they may unknowingly break laws and cause their organisation legal problems
     • Document may include what sanctions might be applied to users who violate the policy, and what personal information should/shouldn't be entered into the network
   • Backup
     • States what data will be backed up from the network, how often it will be backed up, where it will be physically stored, and how it would be used to restore any lost data.
       • Without one, data is more likely to be permanently lost.
   • Disaster recovery
     • Describes how an organisation's IT infrastructure will keep it running in the event of a disaster such as a fire or flood.
       • May contain parts of the backup and failover policies.
       • Important as an organisation without an IT capability is likely to lose income as well as consumer confidence
   • Archive
     • An archive is long-term storage for data that is not needed on a day-to-day basis anymore
       • The policy stipulates what data is to be archived, where it will be stored, and how old data needs to be before it is archived.

Imagens e arquivos do mapa