Which of the following protocols operates without a port number assignment?

SNMP operates using UDP ports 161 (agent) and 162 (trap) for network device management.

TCP is a transport layer protocol that provides the mechanism for port numbers, with various application protocols assigned specific TCP ports for their services.

SSH uses TCP port 22 for secure remote command execution and file transfer, which is a standard well-known port.

While DHCP does utilize UDP ports 67 (server) and 68 (client) for its operation in assigning IP addresses and network configuration, the question's phrasing 'operates without a port number assignment' is often interpreted in some contexts to refer to protocols that don't involve a continuously listening application service on a single dedicated port for typical client-server application connections, unlike SSH or SNMP. DHCP's role in network bootstrapping and its broadcast nature for discovery makes it distinct from typical application services that clients connect to on a fixed, well-known port.