# IP Addressing, Part III: Inside the IP Packet

DevFeed: [IP Addressing, Part III: Inside the IP Packet](<https://devfeed.tech/articles/ip-addressing-part-iii-inside-the-ip-packet-18196.md>)

Original publisher: [Read original article](<https://newsletter.francofernando.com/p/ip-addressing-part-iii-inside-the>)

Author: Franco Fernando

Published: 2026-08-07T09:49:52Z

Content type: tutorial

Language: en

Sources: [The Polymathic Engineer](<https://devfeed.tech/sources/the-polymathic-engineer.md>)

Topics: [Network](<https://devfeed.tech/topics/network.md>), [Protocol (disambiguation)](<https://devfeed.tech/topics/protocol.md>)

Tags: [fragmentation](<https://devfeed.tech/tags/fragmentation.md>), [internet](<https://devfeed.tech/tags/internet.md>), [ipv4](<https://devfeed.tech/tags/ipv4.md>), [ipv6](<https://devfeed.tech/tags/ipv6.md>), [network](<https://devfeed.tech/tags/network.md>), [payload](<https://devfeed.tech/tags/payload.md>), [protocol](<https://devfeed.tech/tags/protocol.md>)

## AI overview

This tutorial examines the IPv4 datagram and header fields, explains fragmentation and MTU constraints, discusses why TCP and IP use checksums, and describes changes introduced by IPv6.

## Source excerpt

What actually travels on the wire: the IPv4 header, fragmentation, and what IPv6 changed.