Cisco Systems, Inc This document provides a stepwise migration between IPv4 and IPv6 with baby steps from an IPv4-only stack/gateway/ISP to an IPv6-only version, that allows portions of the nodes and of the networks to remain IPv4, and reduces the need for dual stack and CG NATs between participating nodes. A first mechanism named YADA to augment the capacity of the current IPv4 Internet by interconnecting IPv4 realms via a common footprint called the shaft. YADA extends RFC 1122 with the support of an IP-in-IP format used to forward the packet between parallel IPv4 realms. This document also provides a stateless address and IP header translation between YADA and IPv6 called YATT and extends RFC 4291 for the YATT format. The YADA and YATT formats are interchangeable, and the stateless translation can take place as a bump in the stack at either end, or within the network at any router. This enables an IPv6-only stack to dialog with an IPv4-only stack across a network that can be IPv6, IPv4, or mixed. YATT requires that the IPv6 stack owns a prefix that derives from a YADA address and that the IPv4 stack in a different realm is capable of YADA, so it does not replace a generic 4 to 6 translation mechanism for any v6 to any v4.