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

=== Networking Fundamentals - Module 1 ===
Lesson 1 - Network Devices

Lesson 2 - OSI Model

Lesson 3 - Everything Hosts to do speak on the Internet

Lesson 4 - Everything Switches do to facilitate communication

Lesson 5 - Everything Routers do to facilitate communication

Lesson 6 - Networking Protocols
- 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

====

🖧 Full Networking Fundamentals series (Module 1 - all FREE):

📜 Studying for your CCNA?

🧮 Want to learn Subnetting?

🔐 Want to learn about SSL, TLS, and Cryptography?

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.

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[PracticalNetworking]

But what about the TCP Masterclass?

I have about 10-12 lessons scoped out for a comprehensive TCP Masterclass, and I'd love to create it at some point.

When I released the first three lessons, I offered a challenge: If any one video garnered 100k views in the first 6 months, I would create the full TCP Masterclass. Unfortunately, we didn't meet that goal, so I had to prioritize other projects.

But I haven't given up hope! *If you are interested in seeing the full TCP Masterclass developed, then the best way to bring that to fruition is to spread the word about this content*.

Doing so will help others fully understand TCP and UDP and bring me closer to committing to creating the full series... Plus, think of all the Internet Points you can get for sharing this series (likes, karma, follows, etc) 😉


Otherwise, I genuinely hope you got a lot out of the first three lessons. Thank you for all the encouraging words in the comments. =)

[jamess]

Ed, I just wanted to take a moment to express my gratitude for the outstanding educational content that you provide on your YouTube channel. The educational network courses that you have created is one of the best on the platform, offering a wealth of information on a wide range of topics. Your courses are well-structured and easy to follow, making it accessible to learners of all levels. The level of detail and expertise you bring to each of your lessons is truly exceptional, and your passion for teaching shines through in every video.

[Nayab-mw]

The idea behind dividing the concepts into several ideas and explaining it one by one in detail it's just awesome.Loved the way you taught TCP.🙇‍♂️

[ALbed]

The most comprehensive explanation of TCP I have ever watched. I am looking forwarding for the full TCP master class.

[khalidjibril]

I don't normally comment on Youtube videos but I just had to say that this is one of my favourite explanation videos ever. The video was super clear, easy to follow and the diagrams were icing on the cake. Thanks a lot mate!

[shellohd]

I've never seen someone that is able to compress lectures long of material into 44 mins of video white taking the animations into consideration.. Keep up with the content !

[dragonbg]

I would rate you top 1 teacher on youtube. Not only networking teacher, but like your networking teaching is the best teaching compared to teachers in any field.

[sididoueida]

the most comprehensive explanation of TCP I've ever seen. Amazing

[karthik]

This channel deserves better. Wonderful explanation. Learnt this clearly after 4 yrs in networking field

[leonardoffor]

Just finished this series and I must say I'm thoroughly impressed. You are God sent Ed. Thanks for making this free and accessible for all.

[seradfb]

I had gone through about 4 videos which left me a bit confused, but found your video had excellent clarity. Each point was explained without ambiguity and really helped me to get it. Thanks a lot!

[ashutoshmahapatra]

Just a word of appreciation I've networking exam today and your videos have gave a in-depth practical understanding that's very rarely found in others! :)

[privacy]

After watching every video on YouTube, I found this one, and it’s absolutely the best guide I’ve ever seen! I understood everything, and you always answer every question I’ve had in my head. You’re the best mentor ever for these topics. Thank you so much

[RohitVerma-whki]

One of the best explanation of TCP i have ever seen. Thank you for making such informative and easy to understand vidoes for the complicated topics.

[fakeaccount]

Please continue the series . words cant explain how useful your content is .excellent animated content even normal people can understand the topic easily .

[СеваЦук]

I was looking for clear step by step explanation of how tcp works, glad that I found your channel :)

[cslb]

Fantastic work here as always Ed. Its really a shame that millions of tubers aren't into networking. For those who are lets help share these amazing vids. Looking forward to the course!

[mumtahinaparvin]

Before coming to this channel, i used to think i was the only one weak at networking and i had no possibility to learn it. But now i think it is possible to be boss at networking thanks to you.🥰

[TheDavood]

I have never commented on YouTube videos throughout these years, but you made me do so with this video. This is the most comprehensive TCP video that I've ever seen. I watched your routing protocol videos, and those were awesome too. Please keep your videos "free" for those of us who live in countries where paying in dollars is so expensive that we can't afford it

[vincecater]

Another brilliant video about TCP connection!