9.28 Summary

As you’ve seen, understanding the positions and roles of the various network layers is critical to understanding how Linux networking operates and how to perform network configuration. Although we’ve covered only the basics, more advanced topics in the physical, network, and transport layers are similar to what you’ve seen here. Layers themselves are often subdivided, as you just saw with the various pieces of the physical layer in a wireless network.

A substantial amount of action that you’ve seen in this chapter happens in the kernel, with some basic user-space control utilities to manipulate the kernel’s internal data structures (such as routing tables). This is the traditional way of working with the network. However, as with many of the topics discussed in this book, some tasks aren’t suitable for the kernel due to their complexity and need for flexibility, and that’s where user-space utilities take over. In particular, NetworkManager monitors and queries the kernel and then manipulates the kernel configuration. Another example is support for dynamic routing protocols such as Border Gateway Protocol (BGP), which is used in large internet routers.

But you’re probably a little bit bored with network configuration by now. Let’s turn to using the network—the application layer.