Book Image

Learn Wireshark, - Second Edition

By : Lisa Bock
5 (1)
Book Image

Learn Wireshark, - Second Edition

5 (1)
By: Lisa Bock

Overview of this book

Wireshark is a popular and powerful packet analysis tool that helps network administrators investigate latency issues and potential attacks. Over the years, there have been many enhancements to Wireshark’s functionality. This book will guide you through essential features so you can capture, display, and filter data with ease. In addition to this, you’ll gain valuable tips on lesser-known configuration options, which will allow you to complete your analysis in an environment customized to suit your needs. This updated second edition of Learn Wireshark starts by outlining the benefits of traffic analysis. You’ll discover the process of installing Wireshark and become more familiar with the interface. Next, you’ll focus on the Internet Suite and then explore deep packet analysis of common protocols such as DNS, DHCP, HTTP, and ARP. The book also guides you through working with the expert system to detect network latency issues, create I/O and stream graphs, subset traffic, and save and export captures. Finally, you’ll understand how to share captures using CloudShark, a browser-based solution for analyzing packet captures. By the end of this Wireshark book, you’ll have the skills and hands-on experience you need to conduct deep packet analysis of common protocols and network troubleshooting as well as identify security issues.
Table of Contents (28 chapters)
1
Part 1 Traffic Capture Overview
6
Part 2 Getting Started with Wireshark
11
Part 3 The Internet Suite TCP/IP
16
Part 4 Deep Packet Analysis of Common Protocols
21
Part 5 Working with Packet Captures

Tearing down a connection

When a TCP connection is complete, TCP tears down the connection by exchanging a series of FIN packets, closing the port, and refusing any more requests to communicate. Let's walk through the entire process.

When two hosts are communicating, a TCP conversation goes through several stages:

  • TCP starts with a (three-way) handshake to set up the session. In many cases, there are additional header options that further define the parameters.
  • During the conversation, TCP monitors the communication and acknowledges all bytes received to ensure the complete delivery of the data.
  • Once the conversation is over, TCP ends the session with an exchange of FIN packets between the two endpoints, which indicates that the session is complete.

Let's now take a look at how session teardown is represented in Wireshark.

In the Flows312.pcapng capture, packets 6, 7, 8, and 9 represent the session teardown, as shown here:

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