A modified I2TSWTCM to improve bandwidth fairness in Diffserv

The enhanced time sliding window based Three Color Marker (I2tswTCM), improves bandwidth fairness in Differentiated Services network by providing a proportional fair share of the excess network bandwidth among TCP aggregates. This improvement in fairness is obtained by introducing an adaptive factor based on which the yellow packets are injected into the network. However, the fairness performance is found to vary with respect to `gamma', a constant in this factor. Further, deterioration in fairness occurs as the number of aggregates increase in the network. Hence in this paper, an attempt has been made to circumvent the above fairness issue by replacing `gamma' of I2tswTCM with an adaptive factor that depends on PIR, the number of aggregates and the bandwidth of the network. By this proposed scheme compared to I2tswTCM, more yellow packets are injected into the network in case of excess bandwidth, thereby improving fairness. The algorithm with the modification has been presented and simulations have been carried out with the proposed scheme using NS-2. The results show that the proposed marker is insensitive not only to the number of flows in the aggregate but also to the number of aggregates in the network.