With the increasing need for networked applications and distributed resource sharing, there is a strong incentive for an open large-scale service infrastructure operating over multi-domain and multi-technology networks. Service discovery, as an essential support function of such an infrastructure, is a crucial research challenge today. Cross-domain service discovery is essential for seamless service composition in large-scale, multi- domain, and multi-technology networks. In this paper, we compare the current state-of-the-art service discovery systems to their competence with such requirements. The comparison is conducted based on a set of well-defined criteria, leading to a selection of few approaches that can serve as the guideline in designing a global service discovery system for large-scale and multi-technology networks.