1. A-Level Computing#BristolMet Session Objectives#12 MUST define the term data packet SHOULD describe packet switching and circuit switching COULD explain the difference in the use of packet switching and circuit switching Use ipads to make an informative animation

2. A-Level Computing#BristolMet LAN & WAN Differences Starter: Explain as many differences between a LAN and a WAN as you can. Which network do you think is the most secure and why?? LANWAN All machines and devices are locoal (close proximity) Machines and devices are spread to more remote locations (overseas?) Majority of network connected via physical links (hardwired via cables unless solely using wireless) Will usually incorporate a satellite link if connecting over long distances (international) The organisation usually owns all of the network infrastructure (cables and other network hardware) The network usually requires the use of 3 rd party or public communications mediums (such as BT Internet lines) to complete the network.

3. A-Level Computing#BristolMet Data Packets When data is sent from one machine to another over a network, either through the internet or over a LAN, it needs to be collected together in bundles called packets. Packets – bundles of data ready to be transmitted. The size of the ‘message’ doesn’t matter as packages are a standard size, the bigger the message the more packets sent. A data packet consists of several parts or labels Source Address Destination Address Packet Sequence Number DATA Error Checking (Checksum) Where the file Is coming from Where it is going to Which part of the file it is The data itself Ensuring it is the same as original and not corrupted

4. A-Level Computing#BristolMet Sending data packets When data is bundled into a packet there a 2 ways in which the packet can be sent across a network: circuit switching and packet switching. Circuit Switching – a path between the machines is established first and all packets are sent in order. The path is reserved for the duration of the message and then shuts down Advantages: Packets arrive in the right order. Circuit dedicated to data transfer Disadvantages: Network tied up and could be used more efficiently. It takes a relatively long time to set up the circuit. Packet Switching – Individual packets are sent on to the network and each follows the most convenient route at that time. They will probably arrive in a different order but the number sequence label is read and reordered at the destination machine. Advantages: Does not tie up network and are difficult to intercept messages (more secure) Disadvantages: Under heavy use there can be a delay. Data packets can get lost or become corrupted.

5. A-Level Computing#BristolMet Circuit vs Packet Switching Watch this video clip to help confirm your understanding of the difference between packet and circuit switching. http://www.youtube.com/watch?v=Dq1zpiDN9k4 TASK: In pairs use the iPads to make a fun animation to explain the differences between circuit and packet switching. Highlight how the data is bundled and the advantages and disadvantages of each mehtod.