Regularly, new architectures are proposed to address shortcomings in the current internet. It is not always trivial to evaluate how these proposals would perform in practice. This situation is improved significantly with the introduction of the P4 programming language and programmable network equipment. In this paper we discuss our implementation of one particular future internet architecture, namely SCION. We implemented a SCION router in P4 for switches based on the Intel Tofino ASIC. Having an open source P4 implementation of SCION that runs on high-speed hardware can contribute to its adoption as well as support research in this area. Our work lead to several recommendations for and subsequent changes to the SCION protocol, as well as some generic guidelines when designing protocols. A first analysis of our implementation shows it can process SCION packets at high speeds.