The diversity of EAD environments for Web provides its users with different features that can be applied in the process of teaching and learning at distance. This way, this paper presents an architecture for building remote access laboratories (or Web Labs) following the service-oriented computing approach. In this architecture the application's building blocks are services that can be recursively composed resulting in more comprehensive services. Remote access laboratories can benefit of this approach. Every lab resource (physical or logical) is modeled and implemented as a Web Service and lab experiments are assembled by composing these services. A Web Lab built following the proposed architecture is presented with examples of remote experiments in the field of QoS, which presents the behavior of the architecture front the flows of data in the Diffserv domain.