Analysis And Optimization Of LTP Acknowledgement Delay Transmission In DTN

To meet the requirements of deep space exploration missions and achieve effective transmission of data between the Earth and the planets of the universe,a new network architecture called Delay/Disruption-Tolerant Network(DTN)has been developed to effectively overcome space or restricted communication environments.This paper studies Licklider Transmission Protocol(LTP)designed to provide retransmission-based reliability over links characterized by extremely long message round-trip times(RTTs)and/or frequent interruptions in connectivity.The following research work was done:Firstly,this paper analyzed the reason of ACK delay.According to the influence of ACK delay on LTP block RTT,the optimal value m odel of CP timer under ACK delay is established.By setting CP timer reasonably,unnecessary retransmission of CP can be effectively avoided.Secondly,combined with the influence of bit error rate,a model for the number of bundles to be aggregated within a LTP block to avoid Ack delay is established.From the perspective of the size of Bundle,the influence of ACK delay on LTP block is effectively avoided by the aggregation mechanism of LTP.Thirdly,according to the transmission process of the LTP block,the expected number of transmissions of LTP block is calculated.On this basis,combined with the characteristics of LTP multiple sessions parallel transmission,the LTP file delivery model is established.In order to verify the validity of the proposed model,this paper uses the SCNT simulation experimental platform to simulate the deep space communication environment for real file transmission.It verifies that the optimal value model of CP timer under ACK delay and the model for the number of bundles to be aggregated within a LTP block to avoid ACK delay can effectively improve the LTP transmission performance,and confirms that the LTP file delivery model can be applied to estimated file delivery time in deep space communication.The model proposed in this paper has application and reference value to the DTN architecture and the practical application of LTP in the future.