What is the Internet Core?
The Internet is not a single giant computer. It is a network of interconnected networks. End systems such as laptops, phones and servers communicate by sending data through a collection of interconnected routers and links.
The Big Picture 🌍
The network edge contains end systems and applications. The Internet core is responsible for moving data between those systems across interconnected networks.
Sender
Receiver
Network Edge → Internet Core → Network Edge
Packet Switching
In packet-switched networks, a message can be divided into smaller units called packets. These packets travel through network links and routers towards their destination.
📦 Packet Switching
- Data is divided into packets.
- Network resources are shared.
- Packets are forwarded through routers.
- Well suited to bursty data traffic.
🔗 Circuit Switching
- A dedicated communication path is established.
- Resources may be reserved.
- Traditionally associated with telephone systems.
- Communication follows the established circuit.
What Happens Inside the Internet Core?
Routers receive packets and forward them towards the next part of the network path.
📥 Receive
A router receives a packet through one of its network interfaces.
Why Do We Use Layers?
Networking is extremely complex. Layering divides the communication system into manageable responsibilities. Each layer performs a particular set of functions.
Encapsulation: Data Gains Structure
As data moves down the protocol stack, each layer can add control information needed for communication.
Application Data
Transport Layer
Network Layer
Link Layer
Packet Journey Simulator
Watch a packet travel from one end system through the Internet core to another end system.
Host A
R1
R2
Host B
Ready to transmit.
HOTS Challenge 🧠
A student sends a file from India to a server in another country. The file is divided into packets and travels through several routers. Which concept best explains how the routers move these packets through the Internet?
HOTS Reflection
"The Internet works because complexity is organized: packets move through a distributed core while layers separate communication responsibilities."
Networking Lecture 02
The Internet Core and Layering
Interactive Internet Explorer