Which protocol is connectionless and does not guarantee delivery?

• A. UDP
• B. TCP
• C. SCTP
• D. TLS

Answer: (A)

Connectionless operation means there’s no handshake to establish a path and no built‑in mechanism to ensure every packet arrives or arrives in order. The protocol that fits this description is UDP. It sends individual datagrams without establishing a connection and without any acknowledgments, retransmissions, or sequencing. Because of that, packets can be lost, arrive out of order, or be duplicated, and there’s no automatic recovery or guarantee of delivery.

In contrast, TCP is connection-oriented and uses a reliable delivery model with acknowledgments and retransmissions to ensure data arrives intact and in order. SCTP also provides reliable, ordered delivery with connection setup and multiple streams. TLS is a security layer layered on top of a transport protocol; it doesn’t provide delivery guarantees itself—reliability comes from the underlying transport (for example, TCP).