Novel distributed space mission concepts such as fractionation and federation promise to transform the design and operations approach of future missions. These paradigms require robust communications networking among other technologies. For the first time this paper explores the specifics of communications network protocols to enable Federated Satellite Systems using an opportunistic resource exchange frame open to all kinds of missions. Within satellite federations, participant spacecraft trade resources on a voluntary basis open to collaborative and/or commercial returns. The heterogeneous, mobile, flexible and scalable environment of satellite federations requires networking technologies capable of handling autonomous node discovery and frequent link disruptions. This work leverages existing Mobile Ad-Hoc Networking techniques to propose an FSS network protocol concept making use of OSLR neighbor sensing and store-carry-and-forward BATMAN routing concepts combined with link availability assessments and predictive topology routing. The performance of this protocol is tested through a dedicated network simulator and the FSS simulation toolkit. Results show the benefits of using FSS under this protocol. For a LEO-based scenario, average content delivery latency is improved from 41 minutes to 3.7 minutes by full usage of federated network benefits. Intermediate scenarios, such as 50% time network usage, present an average latency of 18 minutes. The paper ends by highlighting conclusions and next steps for the development of space communications protocols suitable for FSS.