How data flow through the Internet

This chapter explains what happens when someone types www.google.com into a web browser

This chapter constitutes an introduction to the topic of computer networking, emphasizing breadth over depth. This chapter is the perfect introduction to computer networking, coming at the topic from a practical angle.

This chapter is based on the YouTube playlist “Networking Fundamentals” by Ed Harmoush, a Network Engineer and YouTuber based in Seattle, WA, U.S. (Practical Networking).

If you’re looking to become a Network Engineer there is no better start to that journey than this video series. And if you’re in any other IT or tech role then now you have a better idea of what it is those networking folks do all day. —Ed Harmoush (Sep 13, 2021)

After completing the seven lessons of this chapter/module, you will be able to explain what happens when someone types www.google.com into a web browser.

Topics covered

There are seven lessons in this module.

Network devices and their functions – Lesson 1

Key concepts discussed in this post include hosts, IP addresses, networks, repeaters, hubs, bridges, switches, and routers.

Learning objectives

• Understand what hosts are

• Understand the designations of client and server

• Understand what IP addresses are and their hierarchical nature

• Understand what is a network

• Define network devices

• Understand the functions of repeaters, hubs, bridges, switches, and routers

The Open Systems Interconnection (OSI) Model – Lesson 2

Key concepts discussed in this post include the OSI model Physical layer, Data Link layer, Network layer, Transport layer, Session layer, Presentation layer, Application layer, and data encapsulation/de-encapsulation.

Learning objectives

• Understand what is the OSI model

• List the layers of the OSI model and describe their functions

• Understand the types of network devices that operate at each layer of the model

• Know what protocols operate at each layer of the model

• Understand the addressing schemes of layers 2, 3, and 4

Host to host communication in networking – Lesson 3

Key concepts discussed in this post include the Address Resolution Protocol (ARP), how hosts in the same network communicate, and how hosts in different networks communicate.

Learning objectives

• Understand how ARP resolves IP addresses to MAC addresses

• Understand how hosts in the same network send and receive data

• Understand how hosts in different networks communicate over the wire

How switches facilitate communication within a network – Lesson 4

Key concepts discussed in this post include the MAC address table, the four functions of switches (learning, flooding, forwarding, and filtering), unicast vs broadcast frames, and daisy chain switch typology.

Learning objectives

• Understand how switches use the MAC address table

• Understand how switches perform their functions

• Understand how unicast flooding is different from a broadcast

• Understand what are VLANs

• Understand how switches operate when there are multiple switches involved

How routers facilitate communication between networks – Lesson 5

Key concepts discussed in this post include the difference between a router and a host, the routing table, the ARP table, and hierarchical network topology.

Learning objectives

• Understand the difference between a router and a host

• Understand how a routing table can be populated with routes

• Understand how routers use their routing tables and ARP tables to move packets across the Internet

• Understand why you would want to deploy your routers in a hierarchy

Network protocols and their functions – Lesson 6

Key concepts discussed in this post include the TCP/IP model, and the functions of the network protocols ARP, FTP, SMTP, HTTP, SSL, TLS, HTTPS, DNS, and DHCP.

Learning objectives

• Understand what are network protocols

• Understand how the TCP/IP model maps to the OSI model

• List and describe the four parameters every host needs to achieve Internet connectivity

• Understand the roles of the DHCP protocol and the DNS protocol in Internet communication

• Describe the functions of the network protocols ARP, FTP, SMTP, HTTP, SSL, TLS, and HTTPS

When you type www.google.com into a browser – Lesson 7

Learning objectives

• Explain the steps involved in transmitting a packet from one endpoint to another across the Internet

• Understand how the MAC address, ARP, and routing tables facilitate data flow through a network