Solution

The correct answer is (D) Only

Key Points

• UDP (User Datagram Protocol) is one of the core internet protocols. It belongs to the transport layer in the TCP/IP model, similar to TCP (Transmission Control Protocol).
• However, while UDP and TCP share the common goal of delivering data between devices, they are fundamentally different in their operation methods.
• UDP is a connectionless protocol. It does not establish a connection before sending data, thus there is no need for congestion control, flow control, or retransmission, which are all mechanisms aimed at ensuring reliable, ordered delivery of data.

EXPLANATION:

• (A) Congestion control: A mechanism that prevents network congestion by controlling how much data can be sent at a time. TCP uses congestion control to prevent sending too much data at once, but UDP does not implement this.
• (B) Flow control: A method to control the rate at which data is transferred to make sure a fast sender cannot overwhelm a slow receiver. TCP includes flow control, but UDP does not.
• (C) Retransmission: A reliability mechanism in TCP where lost packets are detected and retransmitted. UDP does not have this mechanism — it sends packets without checking if they are received.
• (D) Segment transmission: This refers to the actual transfer of data. Both TCP and UDP perform this function. In UDP's case, it sends data in segments called datagrams. Each datagram is independent and does not require connection setup or teardown processes.

Therefore, out of the provided options, UDP performs only (D) Segment transmission. Hence the correct answer is 3) (D) Only.