Which protocol uses UDP port 161?

The correct choice is SNMP (Simple Network Management Protocol), which operates over UDP (User Datagram Protocol) and specifically uses port 161 for its communication. SNMP is widely used for network management, allowing administrators to monitor network devices, gather performance data, and configure settings.

UDP is chosen for SNMP because it is a connectionless protocol that allows for faster data transmission with less overhead, which is beneficial for the real-time monitoring and management of network devices. Since SNMP often involves sending simple status updates or requests for information, the speed of UDP is more critical than the reliability that TCP (Transport Control Protocol) offers.

In contrast, FTP (File Transfer Protocol) typically uses TCP port 21, as it requires a reliable communication channel for transferring files. HTTP (Hypertext Transfer Protocol) operates over TCP port 80 for web traffic and benefits from the connection-oriented nature of TCP. SSH (Secure Shell) uses TCP port 22, providing secure remote command-line access and session management.

Understanding the correct protocol and its associated port underscores the broader concepts of how various protocols operate, the role of port assignments, and how they fit into the network management landscape.