Network Security Principles and Practices provides an in-depth understanding of the policies, products, and expertise that brings organization to this extremely complex topic. The book takes a behind-the-scenes look at how the Cisco PIX(r) Firewall actually works, presenting many difficult-to-understand and new Cisco Firewall concepts. A comprehensive treatment of VPNs and IPSec is presented in extensive packet-by-packet detail. A complete section devoted to service provider techniques for enhancing customer security.”]
Source: https://www.amazon.co.uk/exec/obidos/ASIN/1587050250/helpnetsecuri-21