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Computer Networking Basics

Which correctly describes UDP?

  1. AIt does not establish a connection or control retransmission and ordering, so its header is small and there is no wait before sending
  2. BIt establishes a connection, retransmits data that did not arrive and puts data back in order at the receiver
  3. CIt delivers data to the destination host using only MAC addresses, without IP addresses
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Answer: A. It does not establish a connection or control retransmission and ordering, so its header is small and there is no wait before sending

UDP is a lightweight protocol that adds only port numbers and a simple error check (checksum) on top of IP; its header is 8 bytes (TCP's is 20 bytes without options). With no connection setup, no delivery confirmation and no retransmission, it is used for voice calls and live video, where a little loss is better than delay, and for DNS, which needs just one query and one response. If reliability is needed, the application provides it; QUIC, used by HTTP/3, implements retransmission and encryption on top of UDP. Connection setup, retransmission and ordering are what TCP does.

  • A. Correct. It is lightweight, but it does not guarantee delivery or order.
  • B. Those are features of TCP.
  • C. UDP is a transport-layer protocol running over IP and is delivered by IP address.
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