170-010 · Question #75
What are two characteristics of UDP? (Choose two.)
The correct answer is A. connectionless D. no congestion control. See the full explanation below for the reasoning.
Question
What are two characteristics of UDP? (Choose two.)
Options
- Aconnectionless
- Buses sequence numbers
- Cuses a sliding window for flow control
- Dno congestion control
How the community answered
(29 responses)- A83% (24)
- B7% (2)
- C10% (3)
Community Discussion
12
Bao N.May 23, 2026A and D are your two picks. UDP is connectionless because it fires packets at the destination without setting up a handshake first, and it has zero congestion control, meaning it just sends and hopes for the best with no mechanism to slow down when the network is hurting. Sequence numbers and sliding windows are TCP territory, not UDP.
Nina C.May 23, 2026That tracks for me, and I would just add that UDP does carry a checksum field for basic error detection, so it is not totally hands-off, it just has no mechanism to do anything about errors once it spots them.
Dervla O.Feb 3, 2026A and D are your answers. UDP is connectionless because it sends datagrams without establishing a session first, and it has no congestion control mechanism, which is exactly why it is fast but unreliable. Sequence numbers and sliding windows belong to TCP, so B and C are out the moment you remember that TCP owns the reliability toolkit.
Goran A.Jun 2, 2026A and D are your picks here, connectionless is the whole point of UDP and the absence of congestion control is exactly what lets it blast packets without handshaking, same reason I do not want a chatty protocol anywhere near my fabric control plane traffic. Quick question though: if UDP has no sequence numbers, what mechanism does the application layer have to detect out-of-order datagrams, and does the 170-010 expect you to know that distinction at the transport layer or does it stop at TCP vs UDP feature comparison?
Orla P.Jun 2, 2026The app has to handle reordering itself, usually by stamping its own sequence numbers into the payload, and 170-010 typically stops at the transport layer feature comparison so you will not be asked to diagram application-layer workarounds, but knowing the reason why helps you answer the "why no sequencing in UDP" question cold.
Wesley A.Feb 1, 2026Missed this exact question my first attempt because I second-guessed myself on D, thinking "no congestion control" sounded too extreme, and I swapped it for B like an idiot. UDP is connectionless and does zero congestion control, that is the whole point of it, which is why things like live video streaming use it and just accept the dropped packets rather than wait for retransmission.
Orla P.May 17, 2026I kept second-guessing myself on D because I associated "no congestion control" with a flaw rather than a feature, and I almost locked in B thinking UDP had to track something, but then I remembered that sequence numbers are a TCP thing, full stop. What sealed it was just going back to basics: UDP is connectionless and it throws packets at the network with zero flow management, so A and D are the ones that actually describe it.
Bao N.May 19, 2026Solid reasoning, though calling it zero flow management might trip someone up on a future question since UDP can sit inside an application layer that does its own rate limiting, so the cleaner framing for exam purposes is that UDP itself has no transport-layer flow or congestion control.
Mei-Ling H.Jan 27, 2026I pick A and C, sliding window proves UDP still manages flow somehow.
Dervla O.Jan 30, 2026Sliding window is a TCP mechanism, not UDP, so C falls apart there. D is the right pairing with A because UDP handles flow management by simply not doing it, leaving that responsibility to the application layer.
Nina C.Jun 3, 2026Okay so I keep coming back to B and A on this one. UDP does not establish a connection before sending data, so connectionless makes total sense to me, that one feels solid. But I also remember reading that UDP uses sequence numbers in the header, because how else would the receiving end know what order the datagrams came in, even if it does not do anything to fix the order? I feel like sequence numbers are baked into the protocol itself at the header level, so B has to be right too. Am I reading my study material wrong, or does anyone else have B locked in?
Goran A.Jun 5, 2026Nina, you nailed A but the sequence numbers are a TCP thing, not UDP. The UDP header is just source port, destination port, length, and checksum, so D is your second pick because UDP gives you best-effort delivery with no reordering or recovery at the protocol level.