Cloudflare Learning: Network Layer
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Reference articles from Cloudflare's engineering education library explaining IP addressing, packets, routing, MTU and how layer 3 relates to the rest of the OSI stack. Useful for building accurate mental models of what happens between two hosts on the internet.
More resources on Network Protocols
Introduction to TCP/IP
You use the Internet through your PC (Personal Computer), laptop, tablet, smartpad, and smartphone every day in everything you do. Through your own PC/laptop, you can easily learn everything about the Internet, and that is what this course is focused on. In this course ‘Introduction to TCP/IP,’ you will learn the operational functions of Internet technologies (which include IPv4, IPv6, TCP, UDP, addressing, routing, domain names, etc.) and your PC/laptop's security and gateway Internet setup and basic principles. In addition, through a simple Wireshark experiment, you will see the TCP/IP packets and security systems in action that are serving your PC/laptop, that serves you.
Practical Networking
Free article series on how packets actually traverse a network, plus deep treatments of ARP, NAT, access control lists, VLANs, and cryptography. Each series builds sequentially toward a working mental model rather than memorised commands.
Wireshark User's Guide
Official documentation for Wireshark, the open-source network protocol analyzer, covering installation, capturing live traffic, display and capture filters, packet dissection and statistics. Readers learn to capture packets and inspect how protocols such as TCP, DNS and HTTP behave on the wire.
Beej's Guide to Network Programming
A free, long-running guide by Brian "Beej" Hall to sockets programming in C, covering TCP and UDP sockets, addressing, client-server structure, and IPv4/IPv6 differences. Readers learn to write working networked programs and understand how applications use the sockets API.
The Bits and Bytes of Computer Networking
Introductory course from Google's IT Support certificate on how computer networks work, covering the five-layer TCP/IP model, Ethernet, IP addressing and subnetting, TCP and UDP, DNS and DHCP, NAT, and troubleshooting tools. Learners can explain and diagnose everyday network connectivity problems.
TCP/IP Illustrated, Volume 1: The Protocols
Protocol-by-protocol treatment of the TCP/IP suite, following real packet traces through ARP, IP, ICMP, UDP, TCP and DNS. Readers finish able to reason about what is on the wire and diagnose network behavior from a capture.