Networks

Networks

1. Topology

   • Ring
     • Disadvantages
       • One faulty wire or computer will result in failure
     • Advantages
       • No collision
       • Number of computers does not affect speed
   • Mesh
     • Advantages
       • Zero failure
       • Multiple transmission can happe at some time
     • Disadvantages
       • Expensive
       • Lots of unecessary connections

2. Topology

   • Star
     • Advantages
       • Not a single collision
       • Easy to add new computer
     • Disadvantages
       • Expensive
       • Failure of hub or switch is catastrophic
   • Bus
     • Advantages
       • Cheap
       • Easy to install
     • Disadvantages
       • High chance of collision
       • More computers mean more collisions

3. TCP/IP Layers

   • Application Layer
     • Provides applications services to users and programs
   • Transport Layer
     • Handles data-consistency functions (Error Checking)
   • Network Layer
     • Provides network addressing and routing (ip addresses)
   • Data Link Layer
     • Prepares and corrects data to be passed to the physical layer.
   • Physical Layer
     • Transmits and receives bits

4. DNS

   • Every computer on the Internet is identified by its IP address
     • This is fine for computers, but hard for humans
   • DNS (Domain Name System) is a system to store Domain Names (bbc.co.uk or google.com) and lookup their IP addresses
   • When you type a web address into a browser, your ISP (internet service provider) sends the domain name to its DNS server, which returns the IP address
     • DNS is essentially a large address book.