How TCP RETRANSMISSIONS Work // Analyzing Packet Loss

In this video we are going to dive into retransmission analysis. When we see them, what caused them? What can we do about them? In this hands-on video, make sure to download the pcap below so you can follow along as we study a problem that was due to a low network MTU on the path.

----------Download the pcap here-----------

== More On-Demand Training from Chris ==

== Live Wireshark Training ==

== Private Wireshark Training ==
Hope this helps Packet People! Please like, share, subscribe!
Chapters:
0:00 Intro
1:01 Configuring Wireshark
1:54 Retransmission Analysis
3:05 The Retransmission Timeout
6:12 Digging Deeper into the Cause
8:39 Other Types of Retransmissions

[predatorishi]

I’m a senior TAC engineer at Cisco and currently mentoring new hires in my team, I have shared your channel for them to brush up their wireshark skills and I must say that my students are super impressed with you Chris, Great Job!! these videos are gold . <3

[tonioyendis]

Learning layer 4 (transport-layer) is crucial to troubleshooting network/application issues! Most app and most server teams don't understand the importance of TCP- tuning; they have little clue about window-scaling/sizing, SACK-tuning or how much retrans is too much. The BDP calculator is your friend as a network-analyst, most of the issues I discover are usually at layer 4 or below.

[axelcastrejon]

These videos are so good I can't believe they aren't more widely recognised

[IK-iurz]

Always facing Retransmission issues, This video is a life save. :)

[bellaambiens]

Very interesting video, you’re now in my go to channels list.

[TheEitler]

way better than the provided lecture notes at university -> best way to learn for the practical exam is to watch your videos! 👍

[atzelepis]

thnk you chris, i am a technical support negineer for several years, feel i am gaining good enough knowledge here

[nacereddinezekri]

Thank you Chris, your way of explaining very complexe things in a simple and direct way is very valuable.

[vedsachit]

One of the best video on explaining the reason for retransmission.. Subscribed your channel.. looking for more videos..on packet analysis

[kadirrangwala]

Amazing Content ! Please continue to upload such videos regularly.

Suggestion for next video: I would like to see PCAP analysis of a voip call with choppy audio/One Way audio.

[RicardoDiaz]

Been learning so much from your videos. Thanks you Chris

[raulbalderrama]

What a valuable video! I have learned too much from you Chris, thanks a lot!

[aminderpuri]

What else is there to say, informative and well presented. Like your videos a lot

[SnortDefence]

Nice post, looking for depth on this topic Chris. Thanks

[davepete]

What causes [TCP Retransmission] [TCP Port numbers reused] and how to fix it?

[socat]

Would love to see a video on SIP packet troubleshooting :)

[ranjanadissanayaka]

boom ...more knowledge transmitted successfully from server(Chris) to client(me).

[ravishere-mnno]

Thank you very much for all the knowledge you have been sharing!!!

[breakingbisley]

Hey Chris, great video. Just a quick confirmation, in the three way handshake, I see the (TX - Sender) has a MSS of 1460 whereas the (RXR - Server) has a MSS of 1440. Could that be a potential problem, or based on the three handshake. Will both parties agree to some diligence in the network like with windowing sizing? Thanks

[luisfelipeortizmartinez]

Hello Chris,

Great videos, on a particular case where we have a constant but high latency, is it a good idea to have frto or is a better approach to deactivate the frto at the source.

Thanks.