Networks: How Do Packets Get Routed?
Computer Science: OCR GCSE, topic 1.3.4
Packet Switching
Packet switching is the process of breaking data down into packets, sending them across the Internet to another computer, and then re-assembling the data.
Sender's local area network
- The sender will generate data in an application on their computer.
- This happens at the application layer.
- The data is split into packets of data.
- This happens at the transport layer.
- Internet Protocol adds IP addresses to each packet.
- This happens at the Internet layer.
- Packets are grouped into frames and sent to the router on the LAN.
- This happens at the Network layer.
Over the Internet
- The sender's router inspects the packet to determine if the destination IP is on the current LAN.
- If it is not then it will send the packet onto the Internet (or other wide area network).
- This happens at the Internet layer.
- Each packet is sent from the sender's router to the destination router via connected routers.
- The path of each packet can be different, which maximises efficient use of the network by avoiding bottlenecks.
Recipient's local area network
- Because they have taken different paths, the packets at the destination will be in the wrong order.
- These packets are unpackaged and reassembled into the correct order using the sequence number of each packet.
Test yourself on Networks: How Do Packets Get Routed?
Process on the Sender's Local Area Network (LAN)
Process of Routing over the Internet
How is network usage optimised?
Each packet takes a different route to its destination. Why is this optimal?