NETWORKS

NETWORKS

1. topologys

   • MESH
     • Each computer is connected to one or more other computers
     • A full mesh has every computer connected to every other computer A partial mesh has only some of the computers connected
   • STAR
     • All computers are connected to a central hub or switch.
     • A hub sends each message to all the other computers A switch checks the address and sends it only to the correct one
     • Advantages
       • Easy to add new computers
       • Failure of a cable or computer is not catastrophic
       • No collisions
     • Disadvantages
       • Failure of hub/switch is catastrophic and difficult/expensive to fix
         • Expensive (requires hub/switch and lots of cabling)
   • RING
     • Each computer is connected to two other computers in a ring formation
     • If the data is for itself, it reads it, if not it transmits it to the next computer
     • DISADVANTAGES
       • One faulty cable or faulty computer will result in catastrophic failure
       • More difficult to add new computers
     • advantages
       • No collisions, as each cable only has one computer able to transmit on it.
       • Number of computers does not affect speed
   • BUS
     • A single cable connects all the computers
       • All the clients and servers connect to this cable Terminators are attached to each end of the cable
     • ADVANTAGES
       • no extra equipment required
         • cheap
           • Easy to install
     • DISADVANTAGES
       • High chance of collisions
         • More computers mean more collisions
           • Damage to the wire results in catastrophic failure
             • Only suitable for small networks

2. NETWORKS

   • All the clients and servers connect to this cable Terminators are attached to each end of the cable
   • LAN
     • A Local Area Network (LAN) is a network confined to one location or organisation
       • Its resources are only accessible by computers on that LAN
   • WAN
     • Its resources are only accessible by computers on that LAN
       • The Internet is an example of a WAN

3. CIRCUIT SWITCHING

   • The route is locked until the communication is complete
     • This means that for a large transmission, other transmissions may be blocked for a long time

4. packet switching

   • Each packet will likely take a different route to its destination
     • The packets will arrive in a different order to which they were sent
       • Each packet needs to be numbered so it can be re-assembled in the right order

5. TCP/IP STACK

   • APPLICATION
     • TRANSPORT
       • NETWORK
         • DATA LINK
           • PHYSICAL
             • transmits and receives bits
           • prepares and corrects data to be passed to the physical layer
         • provides network addressing and routing ( ip address )
       • handles data consistency functions ( error checker )
     • provides applications services to users and programs

6. ipv4

   • There are more than 4.2 billion devices on the Internet, so there aren’t enough IP addresses to assign one to each device

7. ipv6

   • This is 2128 possible addresses
   • While IPv4 is still the main system used on the Internet, there is a newer version called IPv6 IPv6 uses a 128 bit address

8. dns

   • 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.