Smtp-2. ftp-3. http-4. https-smtp (simple mail transfer profile for email), ftp (file transfer protocol), and http/https (hyper text transfer protocol for internet) all use tcp because of the reliable delivery mechanism. smtp uses tcp port 25, ftp uses tcp ports 20 and 21, http uses tcp port 80, and https uses tcp port 443. incorrect answers: a, c: snmp and tftp use udp as the transport mechanism. generally speaking, protocols that use the keywords trivial or simple uses udp, since connectionless, best effort delivery mechanism usually suffice. reference: ccna self-study ccna intro exam certification guide (cisco press, isbn 1-58720-094-5) page 163.
