One of the important things that you can use Wireshark for is application analysis and troubleshooting. When the application slows down, it can be because of the LAN (quite uncommon in wired LAN), the WAN service (common due to insufficient bandwidth or high delay), or slow servers or clients (we will see this in TCP window problems). It can also be due to slow or problematic applications.

The purpose of this chapter is to get in to the details of how applications work, and provide some guidelines and recipes for isolating and solving these problems. In the first recipe, we will learn how to find out and categorize applications that work over our network. Then, we will go through various types of applications, see how they work, how networks influence their behavior, and what can go wrong.

In this chapter, we will learn how to use Wireshark in order to resolve and troubleshoot common applications that are used in an enterprise network. These are FTP, various e-mail protocols, Microsoft Terminal Server and Citrix, databases, NetBIOS protocols, and others.