The Internet & Protocols

🔗 Internet Protocols

Part 1 of 7 — TCP/IP, HTTP, and How the Internet Works

The Protocol Stack

The Internet uses layered protocols, each handling a specific job:

🔑 Each layer adds its own header to the data (encapsulation). The receiving end removes headers layer by layer.

Key Protocols

IP (Internet Protocol)

• Assigns a unique address to every device
• IPv4: 32-bit addresses (e.g., 192.168.1.1) — about 4.3 billion addresses
• IPv6: 128-bit addresses (e.g., 2001:0db8::1) — virtually unlimited addresses
• IPv6 was created because IPv4 addresses are running out

TCP (Transmission Control Protocol)

• Guarantees reliable, ordered delivery
• Breaks data into packets, numbers them, and reassembles at destination
• Requests retransmission of lost packets
• Used for: web pages, email, file transfers

HTTP / HTTPS

• HTTP: HyperText Transfer Protocol — how web browsers request and receive web pages
• HTTPS: HTTP Secure — adds encryption using TLS/SSL
• HTTPS prevents eavesdropping on the data in transit

Concept Check 🎯

How a Web Request Works

When you type a URL in your browser:

1. DNS lookup: Browser asks DNS server to translate domain name to IP address
2. TCP connection: Browser establishes a connection to the web server
3. HTTP request: Browser sends a request for the specific page
4. Server response: Server sends back HTML, CSS, JavaScript, images as packets
5. Rendering: Browser assembles and displays the page

Protocols Comparison

Why UDP Sometimes?

• Video calls: a few dropped frames are better than waiting for retransmission
• Gaming: outdated position data is useless even if reliably delivered
• Streaming: better to skip ahead than pause for missing data

Certificate Authorities and HTTPS

• A Certificate Authority (CA) verifies website identity

Applied Recall ✍️

1. The protocol that translates domain names to IP addresses is _______.

2. TCP guarantees reliable delivery; _______ trades reliability for speed and is used in video streaming.

3. HTTPS adds _______ to HTTP, preventing eavesdropping on data in transit.

Protocol Selection 🔍

AP Exam Strategy: Internet Protocols

• Know the protocol layers: Application (HTTP), Transport (TCP/UDP), Internet (IP), Network Access
• TCP = reliable + ordered (web, email). UDP = fast + unreliable (video, gaming)
• IPv4 (32-bit) vs IPv6 (128-bit) — know WHY IPv6 was needed
• DNS = domain name to IP address translation
• HTTPS = HTTP + encryption — the lock icon means encrypted AND authenticated
• Know the 5 steps of a web request: DNS → TCP → HTTP request → response → render

AP-Style Application 🎯

🌐 The Internet & Protocols

Part 2 of 7 — Key Processes

How Information Travels The Internet

Two devices talk by following a stack of protocols — agreed rules at each layer. Each layer hides the layer below it.

Concept Check 🎯

A Single Web Request, Layer By Layer

You click a link to example.com/page:

1. DNS (application layer): browser asks a DNS server, "What's the IP for example.com?" → gets back, e.g., 93.184.216.34.
2. TCP (transport layer): browser opens a reliable connection to 93.184.216.34 on port 80 (or 443 for HTTPS).
3. HTTP (application layer): browser sends "GET /page HTTP/1.1".

🌐 The Internet & Protocols

Part 3 of 7 — Patterns & Examples

Common Internet Patterns

The same shapes recur across services.

Concept Check 🎯

Client / Server vs. Peer-to-Peer

🌐 The Internet & Protocols

Part 4 of 7 — Connections & Interactions

Internet Connections Across the Course

The Internet is the substrate everything else runs on.

Concept Check 🎯

Open Standards As The Internet's Superpower

Anyone can implement TCP/IP. Any vendor's router can interoperate with any other's. This open standardization is why the Internet scaled to billions of devices in 30 years.

Routing As An Algorithm

Routers run algorithms (e.g., BGP) to decide where to forward each packet. These algorithms must adapt to:

• New networks coming online.
• Failed links being removed.
• Congestion shifting traffic to alternate paths.

The result is a network that self-heals as conditions change.

Encryption On The Internet

TLS (Transport Layer Security) wraps TCP connections to provide:

• : an eavesdropper sees ciphertext only.

🌐 The Internet & Protocols

Part 5 of 7 — Change Over Time

How The Internet Has Scaled

The Internet has grown from a few thousand devices to tens of billions. The principles that enabled this scale.

Concept Check 🎯

Address Exhaustion And IPv6

IPv4 addresses are 32 bits → 2³² ≈ 4.3 billion. With smartphones, IoT, and rapid global growth, this isn't enough. IPv6 uses 128-bit addresses → vastly more than the number of atoms on Earth's surface.

Workarounds during transition: NAT (Network Address Translation) lets one public IP serve many devices behind a router.

Cloud And CDNs Changed The Picture

• Cloud computing: applications run on shared, on-demand infrastructure rather than self-hosted servers.

🌐 The Internet & Protocols

Part 6 of 7 — Problem-Solving Workshop

Internet & Protocols Workshop

Apply the layered model and the protocol vocabulary to scenarios.

Concept Check 🎯

Worked Scenario 1: Diagnose A Slow Site

Symptoms: site loads but is slow.

Possible bottlenecks by layer:

Modern dev tools show this waterfall directly.

Worked Scenario 2: Choose A Protocol

🌐 The Internet & Protocols

Part 7 of 7 — AP Review

AP Exam Recap — Internet & Protocols

The protocol facts and architectural ideas most likely to appear on the exam.

Concept Check 🎯

One-Line Definitions