LTP Performance on Near-Earth Optical Links

The Licklider Transport Protocol (LTP) has been designed to cope with long-delay and error-prone scheduled-intermittent links, and thus is envisaged as the Bundle Protocol (BP) “convergence layer” of choice in future Inter-planetary networks (IPN) based on the Delay-/Disruption-Tolerant architecture. Moreover, LTP's remarkable ability to cope with multiple losses when operating in “red” reliable mode also makes it potentially appealing when coupled with Near Earth optical links. The aim of this paper is to assess LTP performance in this scenario, so we have developed a test bed based on real machines, real implementations of BP and LTP, and a channel emulator; this is based on “erasure vectors”, i.e. time series describing the on/off state of the optical link, derived from real data measurements conducted by DLR. Our results show that, when properly configured, LTP is able to use all available bandwidth even under the most severe conditions, which makes it a perfect match to Near Earth Optical links.