The Original "Big Three" Network Applications

1. Remote Login                2. File Transfer              3. Electronic Mail
 - telnet command               - FTP, ftp command            - SMTP, sendmail
 - uses TCP port 23             - uses TCP ports 20 and 21    - uses TCP port 25
 - session-oriented             - session-oriented            - session-oriented
 - low-volume interactive data  - bulk data (files)           - email messages
 - plain text                   - plain text                  - plain text

 - today: ssh (secure)          - today: scp (secure)         - today: ESMTP, IMAPS