Booklet for IT professionals, developers and security specialists on how to utilize IPSec protocol in order to protect data transmission between legacy applications which were created before secure communication became common practice. In many cases it is difficult or even impossible to make necessary changes in old software in order to implement commonly accepted secure protocols such as SSL/TLS. IPSec protocol can be utilized as inexpensive but powerful alternative solution which provides adequately high level of protection. Topics include: what is IPSec and how to use it to secure data transmission, creating and deploying IPSec policy, overview or IPSec authentication types, configuring IPSec Policy with different types of authentication, and more (Article: ~2,180 words).Table of Contents includes:Introduction • TCP/IP Security Vulnerabilities • What is IPSec? • Securing Data Transmission with IPSec • Creating and Deploying IPSec Policy • Selecting IPSec Authentication Type • Configuring IPSec Policy with Kerberos Authentication • Diffie-Hellman Groups • Configuring IPSec Policy with X.509 Certificates Authentication • Configuring Certificate Template • Testing • Conclusion • Resources • About the Author