Networks and Communications

Networks and Communications

1. Types of Network

   • Wide Area Network (WAN)
     • Covers a large geographical area e.g internet
   • Local Area Network (LAN)
     • Covers a small area e.g. school, home, etc.
   • Cabling can be expensive, large network managing is complicated, if file server breaks down the servers become inaccessible, viruses can spread, danger of hacking.
   • Sharing devices saves money, easy file sharing, easy (instant) communication, easy backing up data on file server

2. Internet

   • An international network of computers.
     • WWW is only part of the internet. Other parts include: email, instant messaging and file sharing.
     • Types
       • Dial Up
       • Cable modem
       • Leased line ; A connection that has been paid for by a company, only they can use it and it is a permanent connection between two distinct places.
       • ISDN - Integrated Service Digital Network ; Uses digital transmission and can transfer data and voice at the same time. Faster than dial-up.
       • ADSL - Asynchronous Digital Subscriber Line ; faster than dial-up connection, uses telephone lines.

3. Emails

   • Spam, phishing (scams), viruses can easily spread through attachments, recipient needs access to internet, no guarantee that email will be read.
   • Fast delivery, can be sent whenever, cheap, can be sent to one or several people at once.

4. Definition

   • A number of computers linked together to allow them to share resources. Networked computers can share hardware, software and data.

5. Network Topologies

   • Bus Network
     • Easy to install, cheap
     • If main cable fails, the whole system will too. Slow. Security at risk.
   • Star Network
     • expensive (cable), extra hardware (hubs/switches) required, if hub/switch fails all devices will have no connection.
     • Reliable, high performance, no data collisions
   • Ring Network
     • Quick, no data collisions.
     • If main cable fails, the whole network will too.