Performance of bundle protocol for deep-space communications

Delay/disruption tolerant networking (DTN) was developed to enable automated network communications despite frequent and lengthy link disruptions and long link delay. DTN communications rely heavily on a bundle protocol (BP) that uses the well-known approach of store and forward with optional custody transfer for which a node agrees to hold BP data units, bundles, in memory (or storage) until its successful reception is acknowledged by the next node. However, in the presence of long link disruptions, little work has been done regarding performance modeling of BP for reliable data transfer in deep-space communications. In this paper, we present a study of BP over a relay-based deep-space communications system, characterized by lengthy link disruptions accompanied by an extremely long propagation delay, lossy data links, and asymmetric channel rates. An analytical model is built to estimate the total delivery time of a file (message) that is transmitted as the contents of one or more BP bundles over a deep-space channel. A model is also built to characterize the dynamics of memory occupancy and release when BP is used for reliable data delivery in the presence of link disruptions. The constructed models are validated by running experiments using a test bed.