The effects of quantum size on deficit round robin performance

Round robin (RR) scheduling in packet switched networks with segmentation and reassembly (S&R), provides equal sharing of transmission link resources. ATM networks can be given as an example where RR scheduling can be deployed for equal sharing. With varying packet sizes and in the absence of S&R, packet by packet RR results in unfair sharing in favour of longer packets. Deficit round robin (DRR) scheduling has been proposed to alleviate this problem. Our results show that measures taken to reduce the per packet scheduling complexity of DRR also results in a significant level of unfairness in favor of longer packets. However, such unfairness is only significant at the tail of a data transfer and its effect on the overall data transfer becomes less significant as the size of the transfer increases. On the other hand, RR with S&R does not exhibit the unfairness seen in DRR.