Endpoint Naming for Space Delay/Disruption Tolerant Networking

Delay/Disruption Tolerant Networking (DTN) provides solutions to space communication challenges such as disconnections when orbiters lose line-of-sight with landers, long propagation delays over interplanetary links, and other operational constraints. DTN is critical to enabling the future space internetworking envisioned by NASA. Interoperability with international partners is essential and standardization is progressing through both the CCSDS and the IETF. The DTN architecture, defined in RFC 4838, "uses a flexible naming scheme (based on Uniform Resource Identifiers [RFC3986]) capable of encapsulating different naming and addressing schemes in the same overall naming syntax." Although DTN was originally conceived with a space focus, as the technology underpinning an InterPlanetary Network (IPN), DTN has found increasingly broad application to military networks, wireless sensor networks, village networks, "pocket switched" networks, and peer-to-peer networks. In these latter contexts the generality of the naming structure permits the sophistication of "intentional naming" as recently proposed in Internet Draft draft-pbasu-dtnrg-naming-00. We argue in this paper, however, that when the application domain is limited to the space context a much simplified naming scheme is preferred: names may be essentially tuples (x, y) where x and y are finite non-negative integers identifying "node number" and "service number". This scheme was demonstrated in the DINET deep space flight experiment, and it is currently implemented on nodes in the NASA DTN Experimental Network (DEN). We discuss the rationale for this constrained naming structure, based on considerations of the space context. Alternative naming schemes may also be accommodated in a space DTN node, but we suggest that this simplified scheme should be the minimal naming mechanism that all space DTN nodes must implement. A recommendation for a node number assignment strategy is offered which is bandwidth-efficient and fair to agencies/centers/projects using space DTN. Such assignments could be made by the Space Assigned Numbers Authority (SANA) now being established by the CCSDS.