A modified RIO queue management scheme that reduces the bandwidth skew problem in Assured Service
김효곤 · 한국정보과학회 학술발표논문집 · 1999
In offering a statistical end-to-end guarantee service, typically called Assured Service, in Differentiated Services (Diff-Serv) framework, the biggest issue is its inconsistency. Larger profile TCP flows fail to achieve the guaranteed rate when competing with many smaller profile flows. This phenomenon, which we call bandwidth stems from the fact that larger profile flows take longer time to recover from the congestion window size backoff after a packet drop. Proposed solutions to this problem, therefore, are focused on modifying the TCP behavior. However, TCP modification is not practicable, mainly due to its large installation base. We look to other mechanisms in the Diff-Serv framework to find more realistic solutions. In particular, we demonstrate that RIO, the de facto standard packet differentiation mechanism used for Assured Service, also contributes to the skew. Based on this new finding, we design a modified RIO mechanism called RI+O. RI+O uses OUT queue length in addition to IN and IN+OUT queue lengths to calculate OUT packet drop probability. We show through extensive simulation that RI+O significantly alleviates the skew, expanding the operating regime for Assured Service.