A pool.ntp.org traffic analysis 2007-05-27 (PDF, 2MB) Network security lectures 2007 (in Bulgarian) Datalink and network layer security (PDF, 500KB) Wireless networks security (PDF, 500KB) VPNs and security (PDF, 500KB) Path MTU Discovery and Filtering ICMP by Marc Slemko Some interesting papers and links from back in 2002. Certificates list Free (open source, libre) fonts collection