First and foremost, I would like to thank my family: my parents Israel and Selma; my father, the smartest man on earth, who survived the holocaust weighing 35 kilos alone in the world, and 40 years later became a leading expert in telecommunications; my mother, who taught me so many things; my amazing wife Ena, who has been tolerating me being at work over the last 20 years and more; my children Nadav, Dana, and Idan, whose achievements made my work look so simple. Thanks to my sister Hana, her husband Ofer, and their children.

I would also like to thank many colleagues. First, Reuven Matzliach, who started the Comverse IP college with me in the later 90s, transferring Comverse from TDM to IP networks, and helped me through some difficult times. Along with him, I would like to thank Omer Fuchs and Moshe Sakal for their assistance in this great project. Thanks to many colleagues and friends, who this paper is too short to mention.

Thanks to Lior Tzuberi, for many tips and case studies. Hanan Man, for a very interesting network. Yoel Saban and Rami Kletshevsky for very interesting network designs; your design groups are one of the best I've ever seen. Zvi Shacham, for the data-communication teaching experience I've gained from him. Asi Alajem for a very interesting network and Oren Gerstner for very interesting wireless cases. Chen Heffer, the best security expert I've ever known. Yoni Zini, for helping me with the system part. Ibrahim Jubram, for very interesting cellular cases. Ofer Sela, for very interesting projects. Amir Lavi and Eran Niditz, for very interesting cases. Dimitrios Liappis, for interesting cellular cases. Avner Mimon, for great tips and so many others.

Thanks to many training professionals that I've learned so much from. Thirty years ago I thought giving courses is fun; you taught me it's a profession. Harriet Rubin, Merav Sagi, Rvital Keinan, Guy Einav, Raanan Dagan, and many others.

Special thanks to Yoav Nokrean and his son Eran, who assisted me with many ideas, giving me assistance in all possible ways.

I would also like to thank the many colleagues who worked with me over the years; to customers at home, in Europe, North America, Eastern Asia, and other exotic places. Troubleshooting a network is always the same, the only question is, is it snowing outside or is there an exotic coast nearby with tequila?

Special thanks to the many designers that designed bad networks, to developers that wrote strange implementations for TCP/IP, to IT guys who connected the wrong cables, to engineering departments who thought that you just connect the cables to the boxes and it works. That's the best way to learn networking.

To many thousands of students, thanks to all of them for all the hard questions and the interesting cases that you brought with you; I've learned new things in every course. There is nothing that is more fun than connecting to networks and fixing problems in real time.

My admiration to the networking and security pioneers—Vint Cerf, Bob Kahn, Radia Perlman, Adi Shamir, Ronald Rivest, Van Jacobson, Steven McCanne, and so many others. Without you, we wouldn't have all this.

And lastly to Packt Publishing, for coming up with the idea to write this book and very patiently accompanying me through the process.