This document provides an overview of IPv4 and IPv6, including their differences, deficiencies of IPv4, advantages of IPv6, and strategies for transitioning from IPv4 to IPv6. It discusses IPv4 and IPv6 address formats and header formats. It also covers deficiencies of IPv4 like address depletion and lack of security features, advantages of IPv6 like larger address space and better header format. The transition strategies covered are dual stack, tunneling, and header translation.