Firewalls For Dummies, 2nd Edition
Ronald Beekelaar is a native of The Nethrellands, makes his living as network security consultant, author, and trainer. Ronald frequently trains network administrators on network design and enterprise security topics. He writes articles for several computer magazines, mostly about operating systems and security issues.
Joern Wettern, PhD, is a native of Germany and is a network consultant and trainer. Joern has also developed a range of training materials for a large software publisher, and these materials are used to train thousands of network administrators around the world. He frequently travels to several continents to speak at computer conferences.