The Physical Internet (PI) opens many more options to deliver goods to the end destination, thanks to interconnected services. To exploit such opportunities, routing algorithms must be developed at different levels to make the PI work. In this lecture, the levels will be defined and results obtained will be compared to traditional dedicated solutions. Two main point of views will be distinguished: the shipper (how to specify routing request) and the services provider (how to publish services and make agreements). The main PI principles will be presented as well as their impacts on algorithms, data requirements and performance. Initial results show the potential, but also uncover many research opportunities for services providers to develop new services and shippers to operate their supply chain with the PI.