This document describes a mechanism called Public 4over6, which is
designed to provide IPv4 Internet connectivity over an IPv6 access
network using global IPv4 addresses. Public 4over6 was developed in
the IETF and is in use in some existing deployments but is not
recommended for new deployments. Future deployments of similar
scenarios should use Lightweight 4over6. Public 4over6 follows the
Hub and Spoke softwire model and uses an IPv4-in-IPv6 tunnel to
forward IPv4 packets over an IPv6 access network. The
bidirectionality of the IPv4 communication is achieved by explicitly
allocating global non-shared IPv4 addresses to end users and by
maintaining IPv4-IPv6 address binding on the border relay. Public
4over6 aims to provide uninterrupted IPv4 services to users, like
Internet Content Providers (ICPs), etc., while an operator makes the
access network transition to an IPv6-only access network.