Book Image

Openswan: Building and Integrating Virtual Private Networks

By : Ken Bantoft, Paul Wouters
Book Image

Openswan: Building and Integrating Virtual Private Networks

By: Ken Bantoft, Paul Wouters

Overview of this book

<p>With the widespread use of wireless and the integration of VPN capabilities in most modern laptops, PDA's and mobile phones, there is a growing desire for encrypting more and more communications to prevent eavesdropping. Can you trust the coffee shop's wireless network? Is your neighbor watching your wireless? Or are your competitors perhaps engaged in industrial espionage? Do you need to send information back to your office while on the road or on board a ship? Or do you just want to securely access your MP3's at home? IPsec is the industry standard for encrypted communication, and Openswan is the de-facto implementation of IPsec for Linux.</p> <p>Whether you are just connecting your home DSL connection with your laptop when you're on the road to access your files at home, or you are building an industry size, military strength VPN infrastructure for a medium to very large organization, this book will assist you in setting up Openswan to suit those needs.</p> <p>The topics discussed range from designing, to building, to configuring Openswan as the VPN gateway to deploy IPsec using Openswan. It not only for Linux clients, but also the more commonly used Operating Systems such as Microsoft Windows and MacOSX. Furthermore it discusses common interoperability examples for third party vendors, such as Cisco, Checkpoint, Netscreen and other common IPsec vendors.</p> <p>The authors bring you first hand information, as they are the official developers of the Openswan code. They have included the latest developments and upcoming issues. With experience in answering questions on a daily basis on the mailing lists since the creation of Openswan, the authors are by far the most experienced in a wide range of successful and not so successful uses of Openswan by people worldwide.</p>
Table of Contents (22 chapters)
Building and Integrating Virtual Private Networks with Openswan
Credits
About the Authors
Acknowledgements
About the Reviewers
Preface

No Layers, Just Packets


The IP protocol has no concept of layers. It consists simply of packets. When people talk about layers (often layer 2 or layer 3) they are actually talking about how to stuff IP packets into some transport medium such as coax cables, fiber, WiFi, or Ethernet. We will hardly have to worry about those layers, since IPsec deals with IP packets, and not the physical medium of sending those packets.

If you connect from one machine to the other, you are sending and receiving packets. A connection is nothing more than two machines remembering the state of the packets sent and received. An IP packet consists of an IP header, and the IP body. The header contains information that ensures the packets are passed along until they reach their destination. The header also describes what kind of data is inside the packet. The body is the actual data, or the payload.

Each IP packet's header contains the source address, the IP address of the machine that created the packet (and later on perhaps expects an answer). It contains the destination IP address, the place where this packet is intended to go, and a protocol number. Most protocols also require a port number. The IP header has further space for a bunch of other options or flags that can be set.