Which two statements about UDP are correct? (Choose two.)
LPIC-1 Exam 102-500, objective 109. Networking fundamentals medium
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The options
Choose 2.
Correct It is connectionless: a datagram is sent without first establishing a session
Correct. UDP has no handshake and no connection state. The sender simply emits a datagram to an address and port.
Not correct It guarantees that datagrams arrive in the order they were sent
Wrong. UDP offers no ordering. Datagrams may arrive out of order, duplicated, or not at all; any ordering must be built by the application. Sequencing is a TCP feature.
Correct It is the transport ordinary DNS queries use by default
Correct. A normal DNS query and its reply are a single small exchange, which suits UDP; the client falls back to TCP only for truncated responses and zone transfers.
Not correct It opens a connection with a three-way handshake before sending data
Wrong. The SYN, SYN-ACK, ACK handshake is TCP's. UDP has nothing equivalent.
Not correct It retransmits any datagram that is not acknowledged
Wrong. UDP neither acknowledges nor retransmits. That absence is exactly why it is faster and lighter, and why applications such as VoIP prefer it.
Why
UDP is a thin wrapper over IP that adds only ports and a checksum: connectionless, unordered, unacknowledged. TCP adds the handshake, sequence numbers, acknowledgements, retransmission and flow control, at the cost of latency and overhead. Services built on UDP include DNS queries, DHCP, NTP, TFTP and SNMP; SSH, HTTP, HTTPS, SMTP and FTP use TCP.
Where this comes from
- Cited
- LPI exam objective 109.1
- What it says
- Distinguish the properties of TCP from those of UDP.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 109 and space the ones you get wrong.