Book Image

Network Analysis using Wireshark Cookbook

By : Yoram Orzach
Book Image

Network Analysis using Wireshark Cookbook

By: Yoram 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 (23 chapters)
Network Analysis Using Wireshark Cookbook
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Warning events and understanding them


As described earlier, warning events indicate problems in the application or in communication. In this recipe, we will describe the main events in this category.

Getting ready

Start capturing or open an existing file, and start the Expert Infos window.

How to do it...

  1. From the Analyze menu, open Expert Infos by clicking on Expert Info.

  2. Click on the Warnings: bar. You will get the following window (all events are examples):

    You will see here several event categories:

    • Reassembly problems: These are mostly un-reassembled packets. These are usually indicated as Wireshark dissector problems.

    • TCP window problems: These are mostly zero window and window full problems. These usually indicate slow-end devices (servers, PCs, and so on).

    • Segment loss, segments not in order: These indicate previous segment losses and the ACKed segment that wasn't captured. These are usually TCP problems that are caused by network problems.

How it works...

Wireshark watches the parameters...