So Just How Bad is 0.9% Packet Loss in your Network? --Network Congestion and TCP's impact on Performance (by Mike Canney)

I often get trace files from customers with the comments, "there seems to be some TCP retransmissions" but they are not sure just how that really relates to performance issues they are having.  After all, some amount of retransmissions in an Ethernet Network is normal, right? 

There are certainly safeguards against packet loss in the protocols we use today but just what does it do to the end user experience when packet loss occurs?  Join me as we explore troubleshooting with Wireshark and NetData with an example I ran into recently where we needed to get to the bottom of their performance issue.




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Civilization, As We Know It (by Paul W. Smith)

Destroyed city with phones

Civilization as we know it is all about an advanced state of culture, government, science and industry – the opposite of a savage, unrefined or uneducated condition.  It is presumed to include a plethora of modern comforts and conveniences made possible by science and technology.  After a week of backpacking in the wilderness, or a few hours without an Internet connection, most of us welcome a return to civilization. 

Pundits of diverse persuasion have used the potential end of CAWKI as a call to action.  Congresswoman Nancy Pelosi said the end would come if the GOP took control of the Senate, but she was wrong (at least so far).  A NASA study predicts the culprit will be a combination of resource depletion and unequal wealth allocation, and while that makes sense, it’s also a bit too early to confirm this as well.  Science writer Mark Gibbs suggests it may end with a cough, which in this era of superbugs doesn’t sound too far-fetched.  There is an endless supply of such threats to worry about, but before we can properly focus our anxiety, it helps to consider how we got to this point.

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Baselining and Configuring an IOT Device (by Tony Fortunato)

For those of you who have followed my articles and rants, I've talked about baselining equipment now for many years. in this particular article, I will spend a little bit more time showing you how I baselined a webcam – yup another webcam - what it was doing, and how I reconfigured it to stop the unwanted traffic

A common question I get asked is, “How do you baseline wireless equipment?” You've got several options; you can obviously get a wireless analyzer and capture those packets over the air. Another approach is to work from the access points LAN side by using an inline analyzer between the access point and its switch port. Lastly spanning or mirroring that port to an analyzer works just as well.

It's important to remember that every piece of equipment on your network should be profiled or baselined. You should be familiar with what it should communicate with as well as what it is communicating with.

As I said in the video it doesn't matter if it's a refrigerator, a camera, or a thermostat.  You should always find out how these devices behave because at some point you will have to troubleshoot them.



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How TCP Works - The Receive Window (by Chris Greer)

What does that Window field in the TCP header do? 

Many people ask this question after capturing a trace file with Wireshark. What is the TCP Window? How does it work? How can I use it to troubleshoot performance problems? 

We will answer these questions and more in this nine minute video. Check it out! 

Note: This video focuses on the TCP Receive window. We will cover the send window in another video. 


Author Profile - Chris Greer is a Network Analyst for Packet Pioneer LLC and a Certified Wireshark Network Analyst. Chris regularly assists companies in tracking down the source of network and application performance problems using a variety of protocol analysis and monitoring tools including Wireshark. Chris also delivers training and develops technical content for several analysis vendors. Got network problems? Let's get in touch

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Sharkfest 17 EU - First Thoughts (by Paul Offord)

That's it - another Sharkfest event done and dusted.  Janice and her team did a fantastic job, as always, and the venue was truly spectacular - think of 1930's opulence with a high tech twist and fantastic food.


I was a bit of a late comer - I didn't arrive until midday on the penultimate day - but even so, I could tell it had been a good one.  With attendees from more than 30 countries it was a truly international event.  I was lucky enough to catch several good sessions, and here's a quick summary of some important points I learned.

First up was Kary Rogers.  I think his US session should be compulsory viewing ( see ), and the EU session was another tour de force.  He presents straightforward systematic ways of looking at TCP performance, using some Wireshark features I've never thought to use, all mixed in with a dose of comedy.  The EU session had some new stuff and if it becomes available on the Sharkfest Retrospective area, you are going to want to watch it.

Then I sat in on a session called Developer Bytes Lightning Talks–Development Track, hosted by Roland Knall.  There was some real nitty gritty dev stuff in the session, but

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Intro to Wireshark – Sharkweek Teaser! (by Chris Greer)

Does opening a packet trace stress you out?

If so, you aren’t alone. Packet analysis is tedious, detailed, and can be very time consuming. Usually captures are taken to troubleshoot issues when the stakes are high and failure to find the problem is not an option. You may even have your boss breathing down your neck, expecting you to miraculously see the smoking gun in a matter of minutes, leaving you to wonder if your job is on the line.

Hey, we’ve all been there.

Packet analysis with Wireshark is an art form that can take a long time to develop. Gaining comfort with trace files starts with some basic steps that can go a long way in helping you find the culprit of your performance or security problem. Here, we will take a look at a couple quick hints that all new Wireshark users should know – but we will definitely leave some for the Intro to Wireshark session at Viavi Sharkweek starting on Monday, November 6th. Register here!

Step 1.

Know the packet path and capture well.

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