Moderate Source Routing for DTN Space Networks

This paper proposes a variant of Contact Graph Routing (CGR), the DTN routing algorithm developed by NASA-JPL for space networks. The variant, Moderate Source Routing (MSR), differs from standard CGR as the full route to destination is not recalculated from scratch at each node. Instead, the computed route is saved in a specifically designed extension block of the forwarded bundle (the packet of the Bundle Protocol, used in DTN), to be reused in the following nodes, after validation. In this way the route is recomputed only when necessary, i.e. when it appears to be no longer viable. This approach reduces the computational load, but its major advantage is that it is intrinsically more robust against loops, as described in the paper, where a simple but very challenging test case is analyzed in full detail. MSR was implemented in an experimental version of ION, the NASA-JPL DTN suite.