| The acknowledgement (ACK) strategy of Transmission Control Protocol (TCP) has been modified to delay the ACKs for a configurable period of time that is related to the round-trip time (RTT) to improve its performance in asymmetric links such as space communications. A general relationship between the asymmetric channel ratio and the optimal acknowledgement frequency to achieve maximum throughput is not available. This thesis studies the optimal acknowledgement frequency with respect to the channel RTT to achieve the maximum throughput over various asymmetric, geo-stationary earth orbit (GEO) -satellite links using a test-bed. We found that when the asymmetric channel ratio is as high as about 100/1, the optimal acknowledgement frequency must be increased with an increase in asymmetric ratio to complement the impact of the reduction of acknowledgement channel rate. As a rule of thumb, every two-fold increase in asymmetric ratio requires the optimal acknowledgement frequency to be increased by one acknowledgement per RTT. A regressive model was built to reflect the relationship between the optimal acknowledgement frequency and the asymmetric channel ratio and has been validated. |
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