We have walked through the OSI model and TCP/IP model in the previous sections. We studied TCP, UDP in detail. We have understood how port works. Now, we are capable of understanding what's exactly going on behind the common network applications such as FTP, Telnet and web browser. Cisco only test the definition of common application layer protocols, you can skip the labs in the videos.
The following tutorial videos use wireshark to capture network traffic. Please install wireshark and play on it. Doing them by yourself, everything will be simple and clear.
- E-mail (SMTP): Simple Mail Transfer Protocol allows users to send and receive messages to e-mail applications throughout the internetwork.
- Trivial File Transfer Protocol (TFTP): TFTP is an application that uses UDP. Routers use TFTP to transfer configuration files and Cisco IOS images and to transfer files between systems that support TFTP.
- File Transfer Protocol (FTP): FTP is a reliable, connection-oriented service that uses TCP to transfer files between systems that support FTP. FTP supports bidirectional binary and ASCII file transfers.
- Terminal Emulation (Telnet): Telnet provides the capability to remotely access another computer. Telnet enables a user to log on to a remote host and execute commands.
- HTTP: HTTP is a protocol (utilizing TCP) to transfer hypertext requests and information between servers and browsers.