TCP, UDP, Ports & Sockets

"The Network Layer (Layer 3) gets data to the correct device. The Transport Layer (Layer 4) gets the data to the correct application running on that device."

Learning Objectives

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

• Explain the purpose of the Transport Layer.
• Understand why Layer 4 is essential in modern networking.
• Differentiate between TCP and UDP.
• Explain process-to-process communication.
• Understand ports and sockets.
• Describe multiplexing and demultiplexing.
• Identify common Transport Layer protocols.
• Troubleshoot basic Layer 4 connectivity issues.
• Connect Layer 4 concepts to Docker, Kubernetes, AWS, and modern DevOps practices.

Introduction

Imagine you send a package to a large office building.

The package arrives at the correct building because the address is correct.

However, that isn't enough.

The mailroom still needs to know which office inside the building should receive the package.