Telnet turned remote terminal access into an interoperable Internet service by defining a Network Virtual Terminal and a negotiated command language that could bridge unlike hosts and terminals.
DHCP turned IP configuration into a network service, extending BOOTP with reusable address leases and standardized options so machines could join changing networks without manual per-host setup.
FTP evolved from the early ARPANET into a long-lived Internet protocol for transferring remote files, standardizing authentication, directory commands and separate control and data connections.