IPv4 Run-Out and IPv4-IPv6 Co-Existence Scenarios
When IPv6 was designed, it was expected that the transition from IPv4 to IPv6 would occur more smoothly and expeditiously than experience has revealed. The growth of the IPv4 Internet and predicted depletion of the free pool of IPv4 address blocks on a foreseeable horizon has highlighted an urgent need to revisit IPv6 deployment models. This document provides an overview of deployment scenarios with the goal of helping to understand what types of additional tools the industry needs to assist in IPv4 and IPv6 co-existence and transition. This document was originally created as input to the Montreal co- existence interim meeting in October 2008, which led to the rechartering of the Behave and Softwire working groups to take on new IPv4 and IPv6 coexistence work. This document is published as a historical record of the thinking at the time.