The IPv6 Company D-Link Systems, Inc. NEC Platforms, Ltd. This document specifies the IPv4 service continuity requirements for IPv6 Customer Edge (CE) routers that are provided either by the service provider or by vendors who sell through the retail market. Specifically, this document extends the basic requirements for IPv6 CE routers as described in RFC 7084 to allow the provisioning of IPv6 transition services for the support of IPv4-as-a-Service (IPv4aaS) by means of new transition mechanisms. The document only covers IPv4aaS, i.e., transition technologies for delivering IPv4 in IPv6-only access networks. IPv4aaS is necessary because there aren't sufficient IPv4 addresses available for every possible customer/ device. However, devices or applications in the customer Local Area Networks (LANs) may be IPv4-only or IPv6-only and still need to communicate with IPv4-only services on the Internet.