User privacy on the Internet has become a pressing concern in recent years largely due to the revelations of large scale network surveillance programs. Research initiatives around future Internet architectures (FIAs) offer a unique opportunity to integrate privacy protection measures into the architecture of the network itself. In this paper, we survey the main design challenges of network layer onion routing protocols in FIAs. We empirically investigate the requirements and trade-offs of different design choices. Our goal is to identify promising research directions and incentivize further exploration of the field.