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

The Protocol


Without going into too much detail about all the different kinds of protocols and options, Internet communication today mostly consists of two protocols, TCP and UDP. Note that technically we should be talking about sub-protocols of the IP protocol, but the fact that to do so would actually make things more confusing is only proof that the OSI model is dead.

These two IP protocols, TCP and UDP, have ports, which are simply a way of sub-addressing an IP address. Ports go from 1 to 65535. TCP and UDP connections are therefore characterized by four properties: source address, source port, destination address, and destination port. You can either listen or send on a certain address and port, but you can not use them for both sending and receiving at the same time.

These ports are separate 'entries' into the host. For instance, email is sent using the SMTP protocol, which consists of a TCP connection to the IP address of a mail server on port 25. A DNS server listens on UDP port 53 for questions about translating a hostname to an IP address.

Another well known IP protocol is ICMP. This protocol is used to send error or informational messages. The ping command uses an ICMP packet. The ICMP protocol has no ports. Actually, this protocol is a bit special, as it is a control function of the IP protocol, and not a sub-protocol of the IP protocol.