Network Troubleshooting Tools

Chapter 4. Path Characteristics

In the last chapter, we attempted to answer a fundamental question, “Do we have a working network connection?” We used tools such as ping to verify basic connectivity. But simple connectivity is not enough for many purposes. For example, an ISP can provide connectivity but not meet your needs or expectations. If your ISP is not providing the level of service you think it should, you will need something to base your complaints on. Or, if the performance of your local network isn’t adequate, you will want to determine where the bottlenecks are located before you start implementing expensive upgrades. In this chapter, we will try to answer the question, “Is our connection performing reasonably?”

We will begin by looking at ways to determine which links or individual connections compose a path. This discussion focuses on the tool traceroute. Next, we will turn to several tools that allow us to identify those links along a path that might cause problems. Once we have identified individual links of interest, we will examine some simple ways to further characterize the performance of those links, including estimating the bandwidth of a connection and measuring the available throughput.

Path Discovery with traceroute

This section describes traceroute, a tool used to discover the links along a path. While this is the first step in investigating a path’s behavior and performance, it is useful for other tasks as well. In the previous discussion of ping, it ...