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This section will cover a wide variety of topics in the application of TCP/IP technology. This includes commonly used transport and network layer protocols, the power behind port numbers, and finally standard TCP/IP applications like HTTP, HTTPS, Telnet, e-mail, and FTP. People communicate over the internet primarily in TCP, which is connection-oriented. You can think of it like a conversation that is open and then closed. As we covered earlier, this is accomplished by a three-way handshake. UPD, however, does not have these formal connections and communicates via what we call sessions. A fourth step is added to the three-way handshake, the FIN, in order to end the session. TCP is the most common type of session, interacting with your web browser in order to open a session and download your web pages. UDP requires less overhead and is used by only a few applications, like DHCP. Another format, TFTP, allows small files to be transferred locally. ICMP, or Internet Control Message Protocol, is typically used to check the status of a connection. The "ping" command usually used in the command line is an example of this protocol. IGMP, or Internet Group Management Protocol, works as a multicast protocol for internet connections. In these multicast connections, information is broadcasted to multiple devices in a group. To pass the certification exam you need to memorize commonly used port numbers. Every TCP/IP app uses port numbers to communicate between the server and the client. Port numbers between 0 and 1023, or well-known port numbers, need to be memorized for this exam. 1024-5000 encompasses pseudo-random ephemeral ports, and 49152-65535 covers dynamic port numbers. Finally, 1024-49151 are registered ports. HTTP, or Hypertext Transport Protocol, is the main protocol used in browsing the web. Web servers use this protocol to deliver web pages to browsers. HTTPS provides a safer alternative to HTTP, and Telnet is an early communication tool used on port 23 that is still used to this day. SSH, or secure shell, eventually came to replace Telnet. E-mail is another web service that operates on SMTP, or TCP port 25. IMAP4, or Internet Message Access Protocol version 4, allows you to search for specific keywords. A good alternative to these protocols would be web services or native e-mail applications. FTP, or file transfer protocol, operates on 20-21 and is being replaced by SCP and SFTP.