Internet architecture is facing at least three major challenges. First, it is running out of IPv4 addresses. IPv6 offers a long-term solution to the problem by offering a vast amount of addresses but is neither supported widely by networking software nor has been deployed widely in different networks. Second, end-to-end connectivity is broken by the introduction of NATs, originally invented to circumvent the IPv4 address depletion. Third, the Internet architecture lacks a mechanism that supports end-host mobility and multihoming in a coherent way between IPv4 and IPv6 networks. We argue that an identifier-locator split can solve these three problems based on our experimentation with the Host Identity Protocol. The split separates upper laye...