Packet CS Thinking Example 3
Follow the full solution, then compare it with the other examples linked below.
Example 3
mediumA 1 MB file is split into 1000 packets. Packet 500 is lost during transmission. Describe what happens next.
Solution
- 1 Step 1: The receiver notices packet 500 is missing (there is a gap in the sequence numbers). It sends a request to the sender asking for packet 500 to be retransmitted.
- 2 Step 2: The sender retransmits only packet 500 (not the whole file). Once received, the receiver slots it into position 500 and continues reassembling. Only 0.1% of the data needed retransmitting.
Answer
The receiver detects the missing packet by sequence number, requests retransmission of only that packet, and reassembles the complete file.
This selective retransmission is why packet switching is efficient. Circuit switching would require restarting the entire transfer. TCP (Transmission Control Protocol) handles this process automatically.
About Packet
A small unit of data transmitted over a network, containing both the data payload (the actual information) and routing information in headers (source address, destination address, sequence number). Large messages are split into many packets, sent independently, and reassembled at the destination.
Learn more about Packet →More Packet Examples
Example 1 easy
What is a data packet and why is data sent in packets rather than as one continuous stream?
Example 2 mediumDescribe what information a packet header contains and why each piece is needed.
Example 4 hardExplain why packets from the same file might take different routes across the internet and arrive ou