Abstract
Despite being established concepts in standards we argue that zones and particularly conduits can benefit from more detailed discussions of their architecture and implementation. In this paper we make three contributions towards this. Firstly, we describe detailed principles for implementing conduits. Secondly, we outline a process for connecting zones with potentially different Security Levels (SLs), expressed in the form of a flow chart. Thirdly, we discuss a few highlighted challenges related to the application of zones and conduits in practice.