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Network Analysis using Wireshark Cookbook

Network Analysis using Wireshark Cookbook

By : Orzach
4.6 (7)
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Network Analysis using Wireshark Cookbook

Network Analysis using Wireshark Cookbook

4.6 (7)
By: Orzach

Overview of this book

Is your network slow? Are your users complaining? Disconnections? IP Telephony problems? Video freezes? Network analysis is the process of isolating these problems and fixing them, and Wireshark has long been the most popular network analyzer for achieving this goal. Based on hundreds of solved cases, Network Analysis using Wireshark Cookbook provides you with practical recipes for effective Wireshark network analysis to analyze and troubleshoot your network. "Network analysis using Wireshark Cookbook" highlights the operations of Wireshark as a network analyzer tool. This book provides you with a set of practical recipes to help you solve any problems in your network using a step-by-step approach. "Network analysis using Wireshark Cookbook" starts by discussing the capabilities of Wireshark, such as the statistical tools and the expert system, capture and display filters, and how to use them. The book then guides you through the details of the main networking protocols, that is, Ethernet, LAN switching, and TCP/IP, and then discusses the details of application protocols and their behavior over the network. Among the application protocols that are discussed in the book are standard Internet protocols like HTTP, mail protocols, FTP, and DNS, along with the behavior of databases, terminal server clients, Citrix, and other applications that are common in the IT environment. In a bottom-up troubleshooting approach, the book goes up through the layers of the OSI reference model explaining how to resolve networking problems. The book starts from Ethernet and LAN switching, through IP, and then on to TCP/UDP with a focus on TCP performance problems. It also focuses on WLAN security. Then, we go through application behavior issues including HTTP, mail, DNS, and other common protocols. The book finishes with a look at network forensics and how to search and find security problems that might harm the network.
Table of Contents (17 chapters)
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16
Index

TCP out-of-order packet events


Another phenomenon that you will see in networks is previous segment loss and out-of-order segments. Both relate to packets arriving out of order, and in some cases indicate a problem.

When you see this on a network connection, it might happen due to network problems or an interruption in capture. In this recipe we will focus on this issue and what it can cause.

Getting ready

Start Wireshark and connect it on a mirrored port. The three phenomena that we want to focus on in this recipe are:

  • Previous segment lost: This occurs when a packet arrives with a sequence number higher than the next expected sequence number on that connection, indicating that one or more packets prior to the flagged packet did not arrive

  • Out-of-order packet: This occurs when a packet is seen with a sequence number lower than the previously received packet on that connection

  • Previous segment not captured (Wireshark Version 1.8.x and higher): This is like the previous segment lost

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