Szechenyi Istvan University Several IPv6 transition technologies have been developed to provide customers with IPv4-as-a-Service (IPv4aaS) for ISPs with an IPv6-only access and/or core network. All these technologies have their advantages and disadvantages, and depending on existing topology, skills, strategy and other preferences, one of these technologies may be the most appropriate solution for a network operator. This document examines and compares the performance of some free software implementations of the five most prominent IPv4aaS technologies (464XLAT [RFC6877], Dual Stack Lite [RFC6333], Lightweight 4over6 [RFC7596], MAP-E [RFC7597] and MAP-T [RFC7599]) and DNS64 [RFC6147].