Bundles Aggregation of Licklider Transmission Protocol Over Lossy and Highly Asymmetric Space Network Channels

Abstract

Licklider transmission protocol (LTP) was developed to provide reliable and highly efficient data delivery over unreliable space network channels. Some preliminary studies on LTP’s aggregation mechanism in space communication networks have been done. However, the effect on LTP aggregation of data losses caused by lossy space channels has been ignored. Data loss is one of the key features that characterize space networks, and therefore its effect on LTP transmission cannot be left out. In this paper, the LTP aggregation mechanism is studied with focus on its characterization and performance over lossy and highly asymmetric space channels. An analytical model is presented for calculating the minimum number of bundles that should be aggregated within an LTP block for transmission over a lossy channel to avoid report segment (RS) transmission delay caused by highly asymmetric channel rates. The model is validated by realistic file transfer experiments over an experimental testbed infrastructure and packet-level analysis of the results. It is concluded that the aggregation threshold derived from the analytical model functions effectively with respect to resolving RS delay effects and decreasing latency in file delivery, leading to higher transmission efficiency.