Learning Objectives

By the end of this chapter, you will be able to:

  • Define HTTP and its role in the World Wide Web.
  • Identify the key protocols used for sending and receiving email.
  • Define FTP and its purpose.

Key Internet Application Protocols

While TCP/IP is the foundational protocol for the internet, several other application-layer protocols run on top of it to provide specific services.

1. HTTP (Hypertext Transfer Protocol)

HTTP is the protocol that powers the World Wide Web. It defines how messages are formatted and transmitted, and what actions web servers and browsers should take in response to various commands. When you type a web address into your browser, your browser sends an HTTP request to the web server to retrieve the page.

  • HTTPS: A secure version of HTTP that encrypts the communication between your browser and the web server, protecting your data from being intercepted.

2. Email Protocols

Sending and receiving email involves several different protocols:

  • SMTP (Simple Mail Transfer Protocol): The standard protocol for sending email.
  • POP3 (Post Office Protocol 3): A protocol for receiving email. It typically downloads the email from the server to your device and then deletes it from the server.
  • IMAP (Internet Message Access Protocol): Another protocol for receiving email. Unlike POP3, IMAP syncs with the mail server, so your emails are available on multiple devices and any changes you make (like deleting an email) are reflected everywhere.

3. FTP (File Transfer Protocol)

FTP is a protocol used to transfer computer files from one host to another over a TCP-based network, such as the internet. It is often used for uploading files to a web server.

Summary

Several key application protocols run on top of TCP/IP to provide the internet services we use every day. HTTP is the foundation of the World Wide Web, enabling communication between browsers and web servers. A combination of protocols—SMTP for sending, and POP3 or IMAP for receiving—manage our email. FTP is a specialized protocol used for transferring files between computers.

Key Takeaways

  • HTTP is the protocol of the World Wide Web.
  • SMTP is for sending email; POP3 and IMAP are for receiving it.
  • FTP is used for transferring files.

Discussion Questions

  1. What is the main difference between HTTP and HTTPS? Why is HTTPS important?
  2. What is the main advantage of using IMAP over POP3 for your email?
  3. Have you ever used an FTP client? What for?