• Unit 3: The Application Layer

    In this unit, we will examine the application layer of the TCP/IP stack. The application layer is where all network processes and applications run. We will explore five of this layer's prominent applications: the Domain Name System (DNS), e-mail protocols, the World Wide Web's Hypertext Transfer Protocol (HTTP), Simple Network Management Protocol (SNMP), and Secure Shell (SSH). Finally, we will discuss socket programming and how it can be used to develop network applications.

    Completing this unit should take you approximately 5 hours.

    • 3.1: Principles of the Application Layer and the Peer-to-Peer Model

    • 3.2: Application-Level Protocols

      There are several application protocols available, but so far, we have only talked about three: Domain Name System (DNS), Electronic Mail (SMTP and POP3), and HyperText Transfer Protocol (HTTP). The DNS protocol allows you to reference resources outside of your network quickly. E-mail protocols allow you to reach out and communicate with friends and family, and HTTP is the popular protocol for accessing webpages on other systems.

      We will also look at the SNMP and SSH protocols. These two protocols are being used more and more in Internet applications. In particular, the SNMP protocol allows administrators to manage an extensive network more efficiently, and the SSH protocol allows us to design virtual private networks over public networks.

      As you read, think about your social networking activities. How do these protocols allow you to communicate using various media, equipment, and file types/software?

    • 3.3: Writing Simple Networked Applications

    • 3.4: Practice Exercises

    • Unit 3 Assessment

      • Receive a grade