Network Systems and Security (Principles and Practice), New Edition is a comprehensive, modern and resourceful textbook for both undergraduate and graduate students. The book started from the meaning of computer systems to understanding what Network systems and security represents in information processing and security. This textbook teaches the TCP/IP Protocol Suite, TCP/IP Concept Example, Ports, Servers and Standards, types of Computer Network Systems Models- Peer to Peer and Client/Server Models. The book also examines the different types of WLAN, WLAN standards, Security Standards, WPA2/802.11i, the steps in Calculating the Subnet of an IP on Networks in both IPv4 and IPv6. This textbook also focuses on the techniques, policies, operational procedures, and technologies needed to design, implement, administer, secure, and troubleshoot Computer Networks and common Security Procedures and Protocols.