Which range defines "well known ports"?

The correct definition of "well known ports" refers to the range of ports from 0 to 1023. These ports are established by the Internet Assigned Numbers Authority (IANA) and are used by specific protocols and services. For instance, HTTP uses port 80, HTTPS uses port 443, and FTP typically operates on ports 21 and 20, all of which fall within this range.

Ports in this category are reserved for system or well-known processes that require consistent behavior across all systems. This designation helps ensure that applications can reliably communicate over the network without conflict, as there are standardized ports assigned for widely used protocols.

The other ranges mentioned do not fall under the classification of "well known ports." The range 1-1024 does not include port 0, and the range 1024-49151 refers to "registered ports," which are used by user or software applications but are not reserved for specific services in the same way as well known ports.