What is the difference between TCP and UDP, and how does this affect interview answer choice for protocol questions?

TCP is connection-oriented with three-way handshake, sequencing, and guaranteed delivery; UDP is connectionless with no acknowledgments or retransmission. TCP uses ports like 80 (HTTP), 443 (HTTPS), 22 (SSH); UDP uses 53 (DNS), 69 (TFTP), 161 (SNMP). In Bangalore interviews at Cisco India or Infosys, protocol choice questions test real-world judgment—answer TCP for reliability-critical apps (file transfer, database replication), UDP for latency-sensitive traffic (VoIP, video streaming, OSPF hellos). Interview tip: Mention TCP overhead (20-byte header vs UDP's 8 bytes) and explain why DNS queries use UDP but zone transfers use TCP—shows depth beyond textbook answers.

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