This document identifies a set of requirements to be taken into consideration in the design of stateless 4/6 solutions. In particular, these requirements cover the way IPv4-embedded IPv6 address and prefix are to be built when embedding the port information. A companion effort, documented at [I-D.bsd-softwire-stateless-port-index-analysis], is required to converge on one or a set of algorithms to be used by all stateless solutions.