China Telecom China Telecom CERNET Center/Tsinghua University Verizon Inc Swisscom For the IPv6 transition, dual-stack deployments require both IPv4 and IPv6 forwarding capabilities to be deployed in parallel. IPv6-only is considered as the ultimate stage where only IPv6 bearer capabilities are used while ensuring global reachability for both IPv6 and IPv4 services(usually known as IPv4aaS). This document proposes a general framework for deploying IPv6-only in one multi- domain underlay network. It lists the requirements of service traffic, illustrates major components and interfaces, IPv6 mapping prefix allocation, typical procedures for service delivery from the perspective of network operation. The document also discusses related security considerations.