How Application Layer Services Work

About this Video

• Video Title: How Application Layer Services Work
• Channel: CBT Nuggets
• Speakers: Keith (implied)
• Duration: 00:09:06

Introduction

This video explains how application layer services, specifically DNS and HTTP, function within the TCP/IP protocol stack. It uses a scenario to illustrate the process of a computer accessing a web server, detailing the communication at different layers (application, transport, network, and data link).

Key Takeaways

• DNS (Domain Name System): Translates domain names (e.g., google.com) into IP addresses. Uses UDP as its transport layer protocol and port 53 as its well-known port.
• HTTP (Hypertext Transfer Protocol): Used for accessing web pages. Uses TCP as its transport layer protocol and port 80 as its well-known port. HTTPS uses the same ports but with encryption.
• Well-Known Ports: Application layer services utilize well-known ports to identify the requested service. The server listens on these ports for incoming requests.
• Source and Destination Ports: Client computers choose a temporary source port for each request, which allows multiple simultaneous requests to be tracked. The destination port is the well-known port of the service being requested.
• Layered Communication: The video details the communication process across the application, transport, network, and data link layers, including IP addresses and MAC addresses.