What is a network packet?
Why Interviewers Ask This
This question tests conceptual clarity. Interviewers want to hear a precise, confident definition before moving to more complex Networking topics. It also reveals how well you can explain technical ideas to non-experts.
Answer
A packet is the fundamental unit of data transmission in a packet-switched network (like the Internet). Large messages are broken into smaller packets for transmission. Each packet contains: a header (source and destination IP, packet length, protocol, TTL, checksum) and a payload (the actual data). Packets from the same message may travel different routes through the network and arrive out of order — TCP reassembles them in the correct sequence at the destination. This approach offers advantages over circuit switching: more efficient use of network resources, fault tolerance (packets route around failures), and the ability to share bandwidth among multiple communications simultaneously. The maximum packet size is the MTU (Maximum Transmission Unit) — typically 1500 bytes on Ethernet. Larger packets are fragmented.
Pro Tip
Before answering, structure your response: one-line definition → real-world analogy → concrete example from a project. This makes even complex Networking answers easy to follow.