Boeing Phantom Works The IETF has embraced IPv6 as the next-generation Internet protocol, but global IPv4 deployment continues in private addressing domains behind Network Address Translators (NATs). This document envisions a long-term IPv6/IPv4 coexistence, with IPv6 addresses serving as identifiers (and sometimes also locators) and IPv4 addresses serving as locators (and sometimes also identifiers). This document proposes an architectural framework for IPv6/IPv4 coexistence called: "IPvLX (IP with virtual Link Extension)".