Modeling the Throughput of the Linux-Based Agile-SD Transmission Control Protocol

Agile-SD is one of the latest versions of loss-based congestion control algorithm (CCA), which has been proposed to improve the total performance of transmission control protocol (TCP) over highspeed and short-distance networks. It has introduced a new mechanism, called agility factor mechanism, which shortens the epoch time to reduce the sensitivity to packet losses and in turn to increase the average throughput. Agile-SD has only been tested via simulation; however, it has not been mathematically proven or evaluated. The contribution of this paper is twofold. First, a new mathematical model for the throughput of NewReno and Agile-SD is proposed. This model is designed using the well-known Markov chains to validate the correctness of Agile-SD and to show the impact of buffer size, multiplicative decrease factor, and maximum limit of agility factor (λ
_max
) on the total performance. Second, an automated algorithm configuration and parameter tuning (AACPT) technique is employed to optimize and automate the configuration of λmax. Furthermore, the numerical results for both NewReno and Agile-SD are compared with the simulation results, in which the validity of the proposed model is confirmed. Moreover, the output of the AACPT is exploited to formulate a new equation, which calculates the optimal λmax from a given β in order to conserve the standard interface of the TCP. This equation increases the scalability of Agile-SD and improves its total performance.