1. Rules of Packet Transmission
(Role of packet switching and routers)

2. Rules of Packet Transmission
How is data sent?
Payload
(the data)
Destination Address
Source
Address
(Packet or Datagram)
When a computer wants to send a message or a file to another computer, it firstly separates the file into a series of data packets.
File
(eg word document, MP3 etc)
Rules of Packet Transmission

3. Rules of Packet Transmission
Using datagram's
Computer network
File
File
Sending a file
Reorganising a file
(Packet or Datagram)
Sending the data
(Packet or Datagram)
Rules of Packet Transmission

4. Rules of Packet Transmission
Sending the packets
(IP Address)
File, DATA D A 1 2 T
Sending computer A
Breaking up the file into packets 3 4 5
Data packets are reassembled
File, DATA
(IP Address) 6 7
Receiving computer
Rules of Packet Transmission

5. Rules of Packet Transmission
Packets via the Router
(IP Address) D A T A
Sending computer
Packets about to be sent out onto the Internet
The router is instrumental in sending packets onto their destination
Data packets are reassembled having reached their destination
(IP Address) D A T
Receiving computer
Rules of Packet Transmission A

6. Rules of Packet Transmission
The Router Gateway D A T A
A ‘mish mash’ of routers send messages on to their destinations
The Router Gateway
The router inspects the computer’s address packets and sends it onto the next router.
Rules of Packet Transmission

7. Rules of Packet Transmission
The Router Gateway D D A A T T A A
Computer A x x
If part of the network fails, then packets are rerouted around the failure.
Rules of Packet Transmission
Computer B

8. Rules of Packet Transmission
The Router Gateway
Advantages of Packet Switching 1
When sending packets, the system is able to survive a partial network failure, as packets are rerouted 2
Packets can be rerouted around failures very quickly and set on a new path 3
The Internet can grow very quickly as its growth is based on the end points not on any centralised control 4
There is no need for Internet routers to notify each other as endpoint connections are formed and dropped 5
The integrity and security of each packet sent is handled by the endpoints, which simplifies the role of the Internet. 6
Each end point need only be aware of the router to which it is connected and optionally a name resolution service.
Rules of Packet Transmission