Unit 6 · Session 3
HTTP, Email, FTP, WWW, Search, and TELNET
Today's focus
- Key Internet Protocols: HTTP, Email, and FTP
- The World Wide Web and Search Engines
- Remote Login (TELNET)
🎯 Learning Objectives
By the end of this session, you will be able to:
- ✅ Define HTTP and its role in the World Wide Web.
- ✅ Identify the key email protocols and define FTP.
- ✅ Differentiate between the Internet and the World Wide Web.
- ✅ Describe the roles of a web browser and a web server.
- ✅ Explain the basic function of a search engine.
Key Internet Protocols: HTTP, Email, and FTP
Beyond TCP/IP: Application Protocols
While TCP/IP provides the internet's foundation, specialized Application Layer protocols handle the services we use daily.
Think of TCP/IP as the postal service, and these protocols as the different types of mail you can send:
- 💌 Letters (Email)
- 📦 Packages (FTP)
- 📰 Magazines (HTTP)
1. HTTP: The Language of the Web 🌐
HTTP (Hypertext Transfer Protocol) is the protocol that powers the World Wide Web. It defines how browsers and servers communicate.
The process is a simple request-response cycle:
- You type a URL in your browser.
- Your browser sends an HTTP Request to the web server.
- The server sends back an HTTP Response containing the webpage content.
🚦 What the Server Says Back: HTTP Status Codes
Every HTTP response starts with a three-digit code that tells the browser what happened.
| Code | Meaning | When you see it |
|---|---|---|
| 200 OK | Success: here is the page | Almost every page you open |
| 301 Moved Permanently | The page has a new address | An old link quietly sends you to the new one |
| 403 Forbidden | You're not allowed to see this | A staff-only page |
| 404 Not Found | There's no page at that address | A mistyped or deleted link |
| 500 Internal Server Error | The server itself broke | A site crashing on results day |
The rule of thumb: codes starting with 2 mean success, 3 mean redirect, 4 mean client error, and 5 mean server error.
Security Matters: HTTP vs. HTTPS 🔒
HTTP
- Standard HTTP
- Unencrypted
- Data sent in plain text
- Vulnerable to interception
HTTPS
- HTTP Secure
- Encrypted communication
- Protects data with SSL/TLS
- Essential for sensitive info
Key Point: Always look for the lock icon! HTTPS protects your passwords, credit card numbers, and personal data.
Practical Application in Nepal 🇳🇵
Using Online Services Securely
When you log into a Nepali service like eSewa, Khalti, or your bank's online portal, your browser uses HTTPS.
This encryption is crucial for protecting your financial details and login credentials from being stolen over public Wi-Fi or other insecure networks.
2. How Email Travels: A Team of Protocols 📧
Sending and receiving email isn't handled by a single protocol. It requires a coordinated effort between multiple protocols.
We'll look at the three main players:
- SMTP: For sending mail.
- POP3: For receiving mail (the old way).
- IMAP: For receiving mail (the modern way).
Ray Tomlinson, inventor of network email
The Email Protocols 📊
SMTP
Simple Mail Transfer Protocol
The standard for SENDING email from a client to a server.
POP3
Post Office Protocol 3
Used for RECEIVING. Downloads email to a single device and often deletes it from the server.
IMAP
Internet Message Access Protocol
Also for RECEIVING. Syncs with the server, allowing access from multiple devices.
POP3 vs. IMAP: Which is for you?
Scenario:
You use a laptop at work, a personal smartphone, and a tablet at home to check your university email. You want to see the same inbox, sent items, and folders on all devices.
Which protocol is better for this situation?
Answer: IMAP! It synchronizes all your actions across all devices by keeping the master copy of your email on the server.
📬 Follow One Email: Kathmandu to London
Sita (sita@gmail.com) emails her cousin Ram (ram@company.co.uk) in London.
- Sita taps Send. Her Gmail app passes the message to Gmail's mail server using SMTP.
- Gmail's server uses DNS to ask: "Which mail server handles company.co.uk?"
- Gmail's server hands the message to that server, again using SMTP. SMTP carries mail from server to server, not just from your app.
- The message waits in Ram's mailbox on his company's server.
- Ram opens his phone. His mail app fetches the message using IMAP, and it appears on his laptop too.
One email uses at least three protocols (SMTP, DNS and IMAP), usually in a few seconds.
🎬 Watch: How One Email Travels
3. FTP: The Heavy Lifter for Files 📂
FTP (File Transfer Protocol) is a specialized protocol designed to transfer computer files from one host to another over the internet.
Common uses include:
- Uploading website files to a hosting server.
- Downloading large software packages or data sets.
- Sharing files that are too large for email attachments.
FileZilla: local and remote panes
🔍 Activity: Which Protocol Is at Work?
Name the protocol for each situation: HTTP or HTTPS, SMTP, POP3, IMAP, or FTP.
1. You open a news article on onlinekhabar.com. HTTPS
2. You press Send on an email in Outlook. SMTP
3. A web designer uploads site files to a hosting server. FTP (today usually its secure form, SFTP)
4. Your inbox looks the same on your phone and laptop. IMAP
5. An old office PC downloads mail and removes it from the server. POP3
6. You log in to Khalti to pay a bill. HTTPS
Summary & Key Takeaways ⚡
- HTTP is the foundation of the World Wide Web, enabling communication between your browser and web servers. HTTPS adds a critical layer of security.
- Email relies on a combination of protocols: SMTP is exclusively for sending, while POP3 or IMAP are used for receiving.
- IMAP is the modern standard for email access across multiple devices, as it syncs with the server.
- FTP is the go-to protocol for transferring files between computers, especially for web development and large file distribution.
The World Wide Web and Search Engines
Internet vs. World Wide Web
They are not the same thing! It's a common misconception.
The Internet 🌐
- The global network of computers.
- The physical infrastructure (cables, routers, servers).
- Analogy: The road network of a country.
The World Wide Web (WWW) 🕸️
- A service that runs on the Internet.
- A system of interlinked documents.
- Analogy: The houses, shops, and destinations along the roads.
⚡ Key Idea: The Web uses the Internet to exist, but the Internet is more than just the Web (it also supports email, FTP, etc.).
Key Components of the Web
How do we access information on the Web? Through a client-server model.
Web Browser (Client)
Software on your device used to view websites.
- Requests web pages.
- Renders HTML, CSS, and JavaScript.
- Examples: Chrome, Firefox, Safari.
Web Server (Server)
Software on a remote computer that stores websites.
- Listens for requests from browsers.
- Serves web pages upon request.
- Examples: Apache, Nginx.
The Web Address: URL
Every resource on the Web has a unique address called a Uniform Resource Locator (URL).
Anatomy of a URL
https://www.tu.edu.np/results
- https:// - The protocol (HyperText Transfer Protocol Secure).
- www.tu.edu.np - The domain name (Tribhuvan University, Nepal).
- /results - The path to a specific resource on that server.
The Problem: Information Overload
The Web contains billions of pages. How can we find anything?
🔍 Enter Search Engines
Definition: A search engine is a software system designed to search for information on the World Wide Web.
How Search Engines Work: A 3-Step Process
1. Crawling 🕷️
Automated "spiders" follow links to discover pages.
2. Indexing 📚
Content is analyzed and stored in a huge database (the index).
3. Ranking 📊
An algorithm sorts results by relevance and authority.
🎬 Watch: Crawl, Index, Rank
Step 1: Crawling
Crawling: The process of systematically browsing the web to discover new and updated content.
- Automated programs called "spiders" or "crawlers" perform this task.
- They start with a list of known URLs and follow hyperlinks on those pages to find new ones.
- This process is continuous to keep up with the ever-changing web.
Step 2: Indexing
Indexing: The process of storing and organizing the content found during crawling.
- Once a page is crawled, the search engine analyzes its content (text, images, keywords).
- This information is stored in a massive database, like a giant library index for the entire web.
- The index allows for nearly instantaneous retrieval of relevant pages.
The purpose of the index is speed. Searching the entire web in real-time is impossible!
📚 How Big Is the Index?
- Google says its index holds hundreds of billions of web pages and is well over 100,000,000 gigabytes in size.
- Try the maths: if you read one page every second, day and night, how long would 100 billion pages take?
- 100,000,000,000 ÷ 31,536,000 seconds in a year ≈ 3,170 years.
That's why search engines search their index, not the live web. They answer from a giant, pre-sorted catalogue in a fraction of a second.
Step 3: Ranking
Ranking: The process of deciding the order in which to display results for a user's query.
- When you search, the engine queries its index, not the live web.
- A complex algorithm evaluates hundreds of factors to determine relevance.
- Factors include keywords, page authority, user location, and freshness of content.
- Examples: Google Search, Bing, DuckDuckGo.
🎯 Why Businesses Fight for Page One
🌱 Organic results
- Earned through ranking, not paid for
- SEO (Search Engine Optimisation): useful content, a fast mobile site, clear titles, and links from trusted sites
- Slow to build, but free per click
💰 Paid results (ads)
- Marked "Sponsored" at the top
- The business pays each time someone clicks
- Instant visibility, but it stops when the money stops
Studies of click data consistently find that the top few results get most of the clicks and very few people visit page two. For a business, ranking is revenue.
Think: A new café in Pokhara wants customers who search "best coffee Lakeside". Should it start with SEO, ads, or both? Why?
Practical Application in Nepal
Search engines adapt results based on your context, like location.
Try This Search
Search for "restaurants near me" on your phone.
- The search engine uses your location in Nepal (e.g., Pokhara, Kathmandu) to provide local results.
- Now search for "latest news". You'll likely see results from Nepali news portals like The Kathmandu Post or Onlinekhabar ranked highly.
- This is the ranking algorithm at work, prioritizing local relevance.
🕵️ Try It: Search Like a Pro
These operators work in Google and most other search engines. Try each one on your phone now.
| Type this | What it does |
|---|---|
"digital divide in Nepal" | Finds that exact phrase only |
site:tu.edu.np results | Searches one website only |
jaguar -car | Leaves out pages that mention "car" |
e-commerce report filetype:pdf | Finds PDF files only |
Challenge: Find a PDF from any .gov.np website about the national budget. Write down the search you used. The shortest search that works wins.
Key Takeaways ⚡
- The Web is a service that runs on the Internet. They are two different things.
- A web browser (client) requests pages from a web server.
- Search engines find information through a three-step process: crawling, indexing, and ranking.
- The index is a critical database that makes fast searching possible.
Remote Login (TELNET)
What is TELNET?
TELNET (Teletype Network) is an early network protocol used to provide a bidirectional interactive text-oriented communication facility.
- Allows users to connect to a remote computer.
- Acts as a "dumb terminal" passing keystrokes directly to the server.
- Commonly used for remote administration of servers and routers.
How It Works
- Client Request: Connection is established via an IP and port (usually port 23).
- Authentication: Username and password are requested.
- Execution: Commands are executed remotely.
- Output: Text output is returned to the user's screen.
The Security Vulnerability ⚠️
TELNET transmits all data in plain text, including usernames and passwords!
- Susceptible to network sniffing.
- Largely replaced by SSH (Secure Shell) which encrypts all traffic.
- Rarely used today on public networks.
⚠️ Real Case: Mirai and Open TELNET Ports
- In 2016, the Mirai malware scanned the Internet for cameras, video recorders and routers that still had TELNET switched on.
- It tried a short list of factory usernames and passwords, such as admin/admin, and took over hundreds of thousands of devices.
- Together, those devices launched some of the largest attacks seen up to that time, briefly knocking major websites offline.
Discussion:
- Why is a plain-text protocol like TELNET dangerous on public networks? What replaced it?
- FTP also sends passwords in plain text. What should a company use instead?
- You buy a Wi-Fi camera for your shop. What two things should you do before connecting it?
Image & Video Credits
Images
- "With Ray Tomlinson.jpg": Andreu Veà, WiWiW.org, CC BY-SA 3.0 — https://commons.wikimedia.org/wiki/File:With_Ray_Tomlinson.jpg
- "DEC VT100 terminal.jpg": Jason Scott, CC BY 2.0 — https://commons.wikimedia.org/wiki/File:DEC_VT100_terminal.jpg
- "FileZilla 3.3.1.png": Adryitan, public domain — https://commons.wikimedia.org/wiki/File:FileZilla_3.3.1.png
- "BalticServers data center.jpg": BalticServers.com, CC BY-SA 3.0 — https://commons.wikimedia.org/wiki/File:BalticServers_data_center.jpg
- URL anatomy, SERP ads-vs-organic, and TELNET plaintext diagrams: custom educational graphics for this deck (Arjan KC / slide-swarm). I7 TELNET plaintext is a teaching mock-up, not a live capture.
Videos (YouTube)
- Sparkle, "How does Email work | Explained under 2 minutes" (0:09 to 1:13), YouTube qddqj5A2mJ0
- CodeAI (Code.org), "The Internet: How Search Works" (1:37 to 2:59), YouTube LVV_93mBfSU
Exam Practice 📝
Short answer
- Expand HTTP, SMTP, IMAP, and FTP.
- Differentiate between the Internet and the World Wide Web.
- What is TELNET? Explain how remote login works.
- Differentiate between HTTP and HTTPS.
Long answer
- Explain how an email travels from sender to receiver, naming the protocols used. Compare POP3 and IMAP.
- Explain how a search engine works, with a diagram.
Revise the answers in the full notes linked on the last slide.
Thank You
Questions before we wrap this hour?
Next: Unit 6 · Session 4 — Web Pages, E-Commerce, Smart City, Intranet and Extranet
📖 Read the full notes: Key Internet Protocols: HTTP, Email, and FTP · The World Wide Web and Search Engines · Remote Login (TELNET)