Microsoft The transition mechanism described in the 6to4 draft [2] [6to4] raises scaling concerns when the matrix of IPv4 connected 6to4- router systems, communicating across to the native IPv6 only connected systems, are on the order of tens to hundreds of millions. This document will address those concerns, offer additional mechanisms for resolving them, and identify use for the scenario of link-local addressing postulated in section 3.1.