Unit 3.2: The Infrastructure of the Internet

Unit 3.2

The Infrastructure of the Internet

IT 204: E-Commerce

Learning Objectives 🎯

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

✅ Describe the internet backbone.
✅ Explain the role of an Internet Service Provider (ISP).
✅ Identify TCP/IP as the core protocol of the internet.

A Global Network of Networks

The internet isn't a single entity. It's a vast, interconnected system of smaller networks operating on a global scale.

Think of it as a hierarchy, from massive global highways down to the street you live on.

The Internet's Hierarchical Structure

Tier 1: The Backbone

🌍 Global high-speed fiber-optic networks.

Tier 2: ISPs

🏢 Regional & local providers connecting to the backbone.

Tier 3: End Users

🏠 You, your home, your business.

Interactive: Classify the Network

Select a network entity, then click the correct tier to classify it.

Click an entity above to select it, then assign it to a tier.

Layer 1: The Internet Backbone 🌐

Definition: A network of very high-speed fiber-optic cables that span the globe, both overland and undersea.

⚡ Capable of transmitting terabits of data per second.
🔗 Undersea cables connect continents, forming the physical basis for global communication.
🏢 Owned and operated by a small number of large telecommunication companies (Tier 1 Providers).

🎬 Watch: Laying the Internet on the Seabed

✂️ Real Case: When Undersea Cables Are Cut

January 2008: two undersea cables near Alexandria, Egypt (SEA-ME-WE 4 and FLAG) were damaged, most likely by a ship's anchor.
Internet traffic across Egypt, the Middle East and India slowed sharply; Indian outsourcing firms had to reroute traffic around the world.
Repairs needed a specialised cable ship and took about two weeks.
Today, more than 95% of intercontinental data still travels through undersea cables, not satellites.

For a landlocked country like Nepal, a problem on a neighbour's cable can slow every online shop at home.

Interactive: Rank by Speed

Click the connection types from slowest to fastest in order.

Your order (slowest → fastest):

Discussion Point: Who Owns the Internet?

This is a common question! The answer is complex.

Answer: No single person or entity owns the internet. However, a handful of large companies (Tier 1 providers like AT&T, Lumen, Orange) own and operate the physical backbone infrastructure.

They "peer" with each other to exchange traffic without cost, forming the core of the global network.

🔀 Internet Exchange Points (IXPs)

IXP: a physical place where many networks (ISPs, content providers) connect and swap traffic directly, usually without paying each other.

❌ Without an IXP

A WorldLink user opens a site hosted on a Nepal Telecom network. Traffic may leave Nepal, go through India, and come back: slower and paid for in foreign bandwidth.

✅ With an IXP

Both ISPs meet at the local exchange in Kathmandu. Traffic stays in the country: faster, cheaper, and works even if the international links are cut.

Big examples: DE-CIX Frankfurt and AMS-IX Amsterdam. Nepal's exchange is npIX, in Kathmandu.

Layer 2: Internet Service Providers (ISPs)

Definition: Companies that provide individuals and businesses with access to the internet.

ISPs act as the "on-ramp" to the internet highway.

They purchase high-speed connectivity from backbone providers.
They then sell this access in smaller packages to their customers.

Interactive: Build the Connection Path

Click Next Hop to trace how data travels from a web server to your device.

Press Next Hop to start the journey.

📖 DNS: The Internet's Phone Book

Routers only understand IP addresses. People remember names. The Domain Name System translates.

You type daraz.com.np. Your device asks its resolver (usually your ISP's).
The resolver asks a root server: "who handles .np?"
The .np server (run in Nepal by Mercantile) points to the server for com.np / daraz.com.np.
That authoritative server returns the IP address. The resolver caches it for next time.

If DNS fails, the shop is still online, but nobody can find it.

Practical Application: ISPs in Nepal 🇳🇵

How does Nepal connect to the global internet?

Major ISPs:

WorldLink
Vianet
Nepal Telecom (NTC)
Classic Tech

Global Connectivity:

Nepalese ISPs connect to the global backbone primarily through terrestrial fiber-optic links via India (e.g., to Mumbai) and China.

This makes our internet access dependent on the infrastructure and policies of our neighbors.

Kathmandu Cable Pole

Interactive: Nepal Connectivity Quiz (1/2)

Test your understanding of Nepal's internet infrastructure.

Interactive: Nepal Connectivity Quiz (2/2)

Test your understanding of Nepal's internet infrastructure.

Analogy: The Internet Highway System 🚗

Let's make this easier to understand:

The Backbone is like the national highway system (e.g., Prithvi Highway) – massive, high-speed, long-distance.
ISPs are the city and town roads that connect to the main highways.
Your Home Network is your personal driveway, giving you access to the local roads.

☁️ Where Websites Live: Data Centres & the Cloud

Data centre: a building full of servers with backup power, cooling and many fibre connections.
Cloud: renting server capacity from someone else's data centres by the hour: Amazon Web Services, Microsoft Azure, Google Cloud.
A shop can rent 2 servers on a normal day and 20 during a festival sale, then scale back down.

"The cloud" is not in the sky. It's someone else's computer, connected to the backbone.

🎬 Watch: Inside a Google Data Centre

🚚 Content Delivery Networks (CDNs)

The problem

A shop's server is in Singapore. Every customer in Kathmandu, Lagos and London fetches every product photo from Singapore.

The CDN fix

Copies of images and videos are cached on edge servers near users. Each customer gets them from the nearest copy.

Examples: Cloudflare, Akamai, Amazon CloudFront; Netflix runs its own (Open Connect) inside ISP networks.

Bring the content to the customer, not the customer to the content.

🎬 Watch: Moving Content Closer

🧮 Worked Example: Latency and Distance

Light in fibre travels about 200,000 km per second, i.e. about 1 ms per 200 km. Distances below are rough cable routes (example figures).

Server in…	Cable distance	One way	Round trip (minimum)
Kathmandu (npIX)	~10 km	0.05 ms	0.1 ms
Mumbai	~2,000 km	10 ms	20 ms
Virginia, USA	~15,000 km	75 ms	150 ms

A product page needing 20 round trips: 20 × 150 ms = 3 seconds from the USA vs 20 × 20 ms = 0.4 s from Mumbai, before any router delays.

This is why CDNs and local IXPs matter: you can't make light faster, only make the trip shorter.

The Protocol: TCP/IP 📜

How does all this complex hardware work together seamlessly?

TCP/IP (Transmission Control Protocol/Internet Protocol) is the fundamental suite of communication protocols that governs the entire system.

It's the universal language and rulebook of the internet.

How TCP/IP Works (A Simple View)

It ensures your data gets from A to B reliably.

Packetizing: TCP breaks your data (e.g., an email) into small pieces called packets.
Addressing: IP adds an address to each packet, like putting a letter in a stamped envelope.
Routing: Routers across the internet read the addresses and forward the packets towards their destination.
Reassembly: TCP at the destination reassembles the packets in the correct order and checks for errors.

This process allows for efficient, fault-tolerant data transmission across a complex global network.

Interactive: TCP/IP Packet Journey

Type a short message and click Next Step to simulate sending it over the internet.

Key Takeaways 🔍

Three core components make up the internet's infrastructure:

The Backbone: A global network of high-speed fiber-optic cables forms the core.
ISPs: They provide the crucial link between the backbone and end-users like us.
TCP/IP: The protocol suite that provides the rules, ensuring reliable communication across the entire network.

💬 Think, Pair, Share

1. A Nepali online shop hosts its site in the USA to save money. List two things its customers will notice, and one fix.

2. If the fibre links through India were cut for a day, which Nepali online services would still work? Why?

3. Should Nepal pay for its own undersea-cable access through a neighbour, or rely on satellites? Argue one side.

Exam Practice 📝

Short answer

What is an internet backbone?
What is an Internet Exchange Point (IXP)? Why is NIXP important for Nepal?
Define packet switching.

Exam Practice 📝 (continued)

Long answer

Describe the layered architecture of the Internet and the role of each layer.
Explain the TCP/IP protocol suite and how TCP and IP work together to deliver a web page.

Revise the answers in the full note.

Image & Video Credits

Images

South Atlantic Express cable map: cvdr, CC BY-SA 4.0 (Wikimedia Commons)
Cable-layer SUBARU: Taiwankengo, CC BY-SA 4.0 (Wikimedia Commons)
DE-CIX switch rack: Stefan Funke, CC BY-SA 2.0 (Wikimedia Commons)
Cables on a pole, Kathmandu: Subhashish Panigrahi, CC BY-SA 4.0 (Wikimedia Commons)
Server room rack: Martinligabue, CC BY-SA 4.0 (Wikimedia Commons)

Videos (YouTube)

Laying the Internet on the Seabed (111–164 s)
Inside a Google Data Centre (62–137 s)
Moving Content Closer (124–184 s)

Thank You

Any questions?

Next Topic: Unit 3.3: Understanding the World Wide Web

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