Learning Objectives

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

Explain how the TCP/IP model organizes network communication into four layers
Identify common networking concepts including IP addresses, DNS, ports, and protocols
Describe how HTTP requests and responses work between a browser and a web server

Prerequisites

A computer with internet access
A terminal application (Terminal on macOS, Git Bash on Windows, terminal on Linux)
Module 02 recommended for terminal skills (curl is used in the lab)

Estimated self-study time:

Activity	Estimated Time
Reading	15 to 20 minutes
Lab	10 to 12 minutes
Quiz	3 to 5 minutes
Total	28 to 37 minutes

Networking is how computers communicate with each other. Every cloud service, every website, and every API call depends on networking. Understanding the basics here will make the VPC, security group, and load balancer concepts in the bootcamp much easier to grasp.

The TCP/IP Model

The TCP/IP model organizes network communication into four layers. Each layer has a specific job, and data passes through all four layers when traveling between computers.

Layer	Name	Purpose	Example Protocols
4	Application	Provides network services to applications	HTTP, HTTPS, DNS, SSH, FTP
3	Transport	Ensures reliable (or fast) delivery of data	TCP (reliable), UDP (fast)
2	Internet	Routes data between networks using IP addresses	IP, ICMP
1	Network Access	Handles physical transmission of data	Ethernet, Wi-Fi

When you type a URL in your browser, the request travels down through all four layers on your computer, across the network, and back up through all four layers on the server.

IP Addresses

An IP address is a unique numerical label assigned to every device on a network. It is how computers find each other.

IPv4 addresses are written as four numbers separated by dots, each ranging from 0 to 255:

192.168.1.100
10.0.0.1
172.16.0.50

Private IP addresses are used within local networks and are not routable on the public internet:

Range	Class	Common Use
10.0.0.0 to 10.255.255.255	Class A	Large networks, cloud VPCs
172.16.0.0 to 172.31.255.255	Class B	Medium networks
192.168.0.0 to 192.168.255.255	Class C	Home and small office networks

Public IP addresses are assigned by internet service providers and are routable on the public internet. When you access a website, your request goes from your private IP, through your router's public IP, across the internet to the server's public IP.

✅Tip: In the AWS bootcamp, you will create Virtual Private Clouds (VPCs) using these private IP ranges. Understanding CIDR notation (like 10.0.0.0/16) comes in Module 03, but knowing that 10.x.x.x is a private range is the foundation.

DNS (Domain Name System)

DNS translates human-readable domain names (like www.example.com) into IP addresses (like 93.184.216.34). Without DNS, you would need to memorize IP addresses for every website.

The DNS resolution process:

You type www.example.com in your browser
Your computer asks a DNS resolver: "What is the IP address for www.example.com?"
The resolver queries DNS servers (root, TLD, authoritative) to find the answer
The resolver returns the IP address 93.184.216.34 to your computer
Your browser connects to that IP address

Ports

A port is a number (0 to 65535) that identifies a specific service running on a computer. Think of the IP address as a building's street address and the port as the apartment number.

Port	Protocol	Service
22	TCP	SSH (secure remote access)
80	TCP	HTTP (web traffic, unencrypted)
443	TCP	HTTPS (web traffic, encrypted)
3306	TCP	MySQL database
5432	TCP	PostgreSQL database
3389	TCP	RDP (Windows remote desktop)

When you configure security groups in AWS (Module 03), you will specify which ports to open and which to block. Understanding ports now makes that configuration intuitive.

TCP vs. UDP

Feature	TCP (Transmission Control Protocol)	UDP (User Datagram Protocol)
Reliability	Guaranteed delivery; retransmits lost packets	No guarantee; packets may be lost
Speed	Slower (overhead for reliability)	Faster (no overhead)
Use cases	Web browsing, email, file transfer, APIs	Video streaming, gaming, DNS lookups
Connection	Connection-oriented (handshake first)	Connectionless (send and forget)

Most cloud services use TCP because reliability matters more than speed for API calls, database queries, and web requests.

Bootcamp connection: Understanding networking fundamentals prepares you for configuring Virtual Private Clouds (VPCs), subnets, and security groups in Module 03: Networking Basics.

How the Internet Works

When you type a URL into your browser and press Enter, a series of steps happens in milliseconds.

HTTP Request/Response Cycle

DNS lookup. The browser resolves the domain name to an IP address.
TCP connection. The browser establishes a TCP connection to the server (three-way handshake).
HTTP request. The browser sends an HTTP request to the server:
```
GET /index.html HTTP/1.1
Host: www.example.com
```
Server processing. The server receives the request, processes it, and prepares a response.

HTTP response. The server sends back an HTTP response:

HTTP/1.1 200 OK
Content-Type: text/html

<html>...</html>

Rendering. The browser renders the HTML into the page you see.

HTTP Methods

HTTP defines several methods (also called verbs) that indicate the desired action:

Method	Purpose	Example
GET	Retrieve data	Load a web page, fetch a list of users
POST	Create new data	Submit a form, create a new user
PUT	Replace existing data	Update an entire user record
PATCH	Partially update data	Change just the user's email address
DELETE	Remove data	Delete a user account

HTTP Status Codes

The server's response includes a status code that tells the client what happened:

Code Range	Category	Common Codes
200-299	Success	200 OK, 201 Created, 204 No Content
300-399	Redirect	301 Moved Permanently, 302 Found
400-499	Client error	400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found
500-599	Server error	500 Internal Server Error, 502 Bad Gateway, 503 Service Unavailable

✅Tip: When troubleshooting cloud applications, HTTP status codes are your first clue. A 403 means a permissions problem. A 502 means the server behind a load balancer is not responding. A 504 means a timeout.

HTTPS and TLS

HTTPS is HTTP with encryption. When you see the padlock icon in your browser, the connection uses TLS (Transport Layer Security) to encrypt all data between your browser and the server. This prevents anyone on the network from reading or modifying the traffic.

In cloud computing, you will configure TLS certificates on load balancers and API endpoints to serve traffic over HTTPS.

Bootcamp connection: Understanding HTTP and DNS prepares you for configuring Application Load Balancers (ALBs) and Route 53 in Module 07: Load Balancing and DNS. In Module 09: Serverless (Lambda), you will build APIs that handle HTTP requests through API Gateway.

Instructor Notes

Estimated lecture time: 20 to 25 minutes

Common student questions:

Q: How much networking do I need to know? A: You need to understand IP addresses, ports, DNS, and the difference between TCP and UDP. Module 03 of the bootcamp covers VPCs and subnets in detail, building on the networking basics covered here.
Q: What is the difference between HTTP and HTTPS? A: HTTPS is HTTP with TLS encryption. All data between the browser and server is encrypted, preventing eavesdropping. In the bootcamp, you will configure TLS certificates on load balancers to serve traffic over HTTPS. Port 80 is HTTP (unencrypted) and port 443 is HTTPS (encrypted).

Teaching tips:

Draw the TCP/IP layers on the whiteboard and trace a web request through all four layers. This visual makes the abstract model concrete.
When troubleshooting, HTTP status codes are your first clue. Walk through a few examples: 403 means permissions, 404 means not found, 502 means the backend is down.

Pause point:

After the networking section, ask students which port SSH uses (22).

Key Takeaways

Networking is how computers communicate. IP addresses identify devices, ports identify services, and DNS translates names to addresses.
HTTP is the protocol that powers the web and cloud APIs. Understanding request methods (GET, POST, PUT, DELETE) and status codes (200, 403, 404, 500) is fundamental.

Previous: Module 02, The Command Line | Next: Module 04, APIs and Programming Basics | IT Fundamentals Overview

AWS Bootcamp: From Novice to Architect Author: Samuel Ogunti License: CC BY-NC 4.0

Module 03: Networking and the Internet