TCP has been the predominate layer 4 protocol that has served the Internet for the last 40 years. In this video we take a deep dive into TCP and illustrate how all of these concepts work together: Sequence Numbers, Acknowledgement Numbers, Window Size, Delayed Acknowledgements, Flow Control, TCP Connection Closures, and FIN + Reset Segments. I've broken up TCP into 12 simple distinct ideas, and if you can understand each of those 12 ideas, then you can say you can understand TCP better than most. Hope you enjoy this TCP deep dive! 00:00 - Intro 00:30 - Pre-Requisites - background knowledge of TCP and UDP 00:48 - Twelve Ideas to understand TCP and the TCP Header 01:32 - Idea 1 - Sequence Numbers and Acknowledgement Numbers 03:00 - Idea 2 - Sequence & Acknowledgement Numbers are tracking BYTES sent and received 04:23 - Understanding Sequence Numbers and Acknowledgement Numbers 06:49 - Idea 3 - TCP Retransmission Timer 09:48 - Idea 4 - Delayed Acknowledgements - Acknowledgments are Cumulative 12:15 - Idea 5 - Window Size and Bytes in Flight 15:00 - Delayed ACKs vs Window Size 15:26 - Idea 6 - Window Size, TCP Headers and Flow Control 18:25 - Idea 7 - TCP is Bidirectional - both peers have SEQ# and ACK# 21:50 - Empty Acknowledgements, Duplicate Acks, TCP analysis, TCP troubleshooting 23:47 - Idea 8 - Initial Sequence Numbers (ISNs) are Random 24:50 - Idea 9 - TCP Three Way Handshake - SYN, SYN ACK, ACK 26:40 - 3-way Handshake, SYN flags, ACK Flags, and the TCP Header 28:40 - Initial Window Size is set in the three-way handshake 29:19 - SYN packets increase the Sequence Number -- The Phantom Byte 30:44 - ACK flag is turned on for all TCP segments, except the initial SYN 31:22 - Idea 10 - Two methods for TCP to close a connection - FIN and RST 32:20 - Idea 11 - FIN Flags and Four Way Connection Closure 34:40 - FIN Flags do not need to be sequential 38:05 - Phantom Byte inside the FIN and SYN Segments 39:38 - Idea 12 - RST Flags instantly terminate a TCP connection 42:00 - Want more? Help me blow up these videos and I'll create the full TCP Masterclass 42:47 - Networking - The Internet, the Cloud, and everything in between TCP vs UDP - Explaining Facts and Debunking Myths - TCP Masterclass - Lesson 1 https://youtu.be/jE_FcgpQ7Co === Networking Fundamentals - Module 1 === Lesson 1 - Network Devices Part 1: https://youtu.be/bj-Yfakjllc Part 2: https://youtu.be/H7-NR3Q3BeI Lesson 2 - OSI Model Part 1: https://youtu.be/LkolbURrtTs Part 2: https://youtu.be/0aGqGKrRE0g Lesson 3 - Everything Hosts to do speak on the Internet Part 1: https://youtu.be/gYN2qN11-wE Part 2: https://youtu.be/JI9Zm2tbUoE Lesson 4 - Everything Switches do to facilitate communication Part 1: https://youtu.be/AhOU2eOpmX0 Part 2: https://youtu.be/G7GyWjJtjNs Lesson 5 - Everything Routers do to facilitate communication Part 1: https://youtu.be/AzXys5kxpAM Part 2: https://youtu.be/Ep-x_6kggKA Part 3: https://youtu.be/zmxLg4jV0ts Lesson 6 - Networking Protocols - https://youtu.be/E5bSumTAHZE - ARP, FTP, SMTP, HTTP, SSL, TLS, HTTPS, DNS, DHCP - Four items MUST be configured for Internet Connectivity Lesson 7 - How Data moves through the Internet - https://youtu.be/YJGGYKAV4pA - Interview question: What happens when you type "site.com" into a web browser? ==== 🖧 Full Networking Fundamentals series (Module 1 - all FREE): https://www.youtube.com/playlist?list=PLIFyRwBY_4bRLmKfP1KnZA6rZbRHtxmXi 📜 Studying for your CCNA? https://www.practicalnetworking.net/index/ccna/ 🧮 Want to learn Subnetting? https://SubnetIPv4.com 🔐 Want to learn about SSL, TLS, and Cryptography? https://www.youtube.com/playlist?list=PLIFyRwBY_4bTwRX__Zn4-letrtpSj1mzY 📖 Other Courses: https://classes.pracnet.net/ 💬 Discord: https://discord.com/invite/yrexngJ If you enjoyed this content, then please tell one other person about this series. Sharing this video is the best way you can thank me and return the favor for this free content. Plus, you can get free Internet Points (karma, likes, retweets, etc) by simply sharing this content across social media communities. =) Thank you. ---