Understanding Linux Network Internals. C. Benvenuti

 This book can help those who already have some knowledge of networking and would like to see how the engine of the Internet—that is, the Internet Protocol (IP) and its friends—is implemented on a first-class operating system. However, there is a theoretical introduction for each topic, so newcomers will be able to get up to speed quickly, too. Complex topics are accompanied by enough examples to make them easier to follow.
 Linux doesn’t just support basic IP; it also has quite a few advanced features. More important, its implementation must be sophisticated enough to play nicely with other kernel features such as symmetric multiprocessing (SMP) and kernel preemption. This makes the networking code of the Linux kernel a very good gym in which to train and keep your networking knowledge in shape.
 Moreover, if you are like me and want to learn everything, you will find enough details in this book to keep you satisfied for quite a while.