Radiation transport problems require, at each time-step, every particle to run to completion. Within a domain decomposed problem this entails a separate looping construct within each time step to loop until all particles have been passed and received and have run to completion. A single particle can pass between multiple domains numerous times before exceeding its time limit or running out of energy. One obvious question is how should the send and receives be structured within the sub-cycles to achieve maximum efficiency. I explore this question in the following sections.