IPv6 deployment is delayed by the existence of millions of subscriber network address translators (NATs) that cannot be upgraded to support IPv6. This document specifies a mechanism for traversal of such NATs. It is based on an address mapping and on a mechanism whereby suitably upgraded hosts behind a NAT may obtain IPv6 connectivity via a stateless server, known as a SAMPLE server, operated by their Internet Service Provider. SAMPLE is an alternative to the Teredo protocol.