This deep dive covers Real-World Example: Sending an Email within Packet Switching for GCSE Computer Science. Revise Packet Switching in 3.5 Fundamentals of Computer Networks for GCSE Computer Science with 15 exam-style questions and 18 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 9 of 12 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Real-World Example: Sending an Email
Imagine you send a 1MB email with photo attachment - here's what happens:
Step 1: Division
Your 1MB email split into ~700 packets of 1500 bytes each. Packet 1 contains first 1500 bytes, Packet 2 contains next 1500 bytes, etc.
Step 2: Headers Added
Each packet gets header: Source IP (your computer), Destination IP (recipient's mail server), Packet number (1 of 700, 2 of 700, etc.)
Step 3: Transmission
Packets leave your computer. Packet 1 might go through London → Paris → Berlin. Packet 2 might go London → Amsterdam → Berlin. Different routes!
Step 4: Routing
Routers check destination IP, forward to next hop. If Paris router is busy, packets reroute through Brussels instead. Dynamic routing!
Step 5: Arrival
Packets arrive at recipient's mail server. They might arrive: Packet 2, Packet 1, Packet 4, Packet 3... Out of order!
Step 6: Reassembly
Mail server sorts using packet numbers, reassembles into original 1MB email. Recipient downloads complete email!
Practice questions for Packet Switching
Which of the following best describes packet switching?
Explain why packets from the same file can travel by different routes through a network. [2 marks]