TCP - 12 simple ideas to explain the Transmission Control Protocol

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
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