Fluid-based analysis of network with DCCP connections and RED routers

In this paper, we model DCCP congestion control mech-anism and RED as independent discrete-time systems using fluid-flow approximation. By interconnecting DCCP con-nections and RED routers, we model the entire network as a feedback system called DCCP/RED. We then analyze the steady state performance and the transient state per-formance of DCCP/RED. Specifically, we derive the packet transmission rate of DCCP connections, the packet trans-mission rate, the packet loss probability, and the average queue length of the RED router in steady state. Moreover, we investigate the parameter region where DCCP/RED op-erates stably by linearizing DCCP/RED around its equi-librium point. We also evaluate the transient state perfor-mance of DCCP/RED in terms of ramp-up time, overshoot, and settling time. Consequently, we show that the stabil-ity and the transient state performance of DCCP/RED de-grade when the weight of the exponential weighted mov-ing average, which is one of RED control parameters, is small. To solve this problem, by adding changes to the func-tion with which RED determines the packet loss probability, we propose RED-IQI (RED with Immediate Queue Infor-mation). We analyze the transient state performance of the feedback system DCCP/RED-IQI where DCCP connections and RED-IQI routers are interconnected. Consequently, we show that DCCP/RED-IQI has significantly better transient state performance than DCCP/RED