Virtual private networks have become an essential part of today's business networks, as they provide a cost-effective means of assuring private internal and external communications over the shared Internet infrastructure. Virtual Private Networks: Technologies and Solutions is a comprehensive, practical guide to VPNs. This book presents the various technology components, concrete solutions, and best practices you need to deploy and manage a highly successful VPN. Readers will find an overview of fundamental VPN concepts and architectures, followed by an in-depth examination of advanced features and functions such as tunneling, authentication, access control, VPN gateways, VPN clients, and VPN network and service management. Specific topics covered include: IPsec, featuring the Authentication Header, Encapsulating Security Payload, Internet Key Exchange, and implementation details; PPTP, L2F, L2TP, and MPLS as VPN tunneling protocols; two-party and three-party authentication, including RADIUS and Kerberos; public key infrastructure (PKl) and its integration into VPN solutions; access control policies, mechanisms, and management, and their application to VPNs; VPN gateway functions, including site-to-site intranet, remote access, and extranet; gateway configuration, provisioning, monitoring, and accounting; gateway interaction with firewalls and routers; VPN client implementation issues, including interaction with operating systems; client operation issues, including working with NAT, DNS, and link MTU limits; VPN management architectures and tunnel and security management; outsourcing and service provider environments.