In the last decades, the explosive growth of the Internet gave rise to the development of several telecommunication technologies, aimed at satisfying the increasing users needs with different degrees of Quality of Service (QoS). Together with the development of QoS technologies, an increasing number of Service Providers and networking companies developed their specific architectural and implementation choices. As a consequence, nested, heterogeneous infrastructures compose today's Internet. End-to-end QoS provisioning in such kind of infrastructures requires proper mapping operations among different protocols and united architectures to interconnect different QoS solutions. In this perspective, the paper analyzes QoS interworking architectures. Two solutions are considered: IP DiffServ and IP switching. They are compared with respect to recent results of standardization bodies and of scientific literature.