Wireless Ad Hoc and Sensor Networks

Congestion Control in ATM Networks and the Internet 111scheme uses NN to estimate the traffic-accumulation rate and uses thisestimate to design a congestion controller, in contrast with other schemes(Floyd and Fall 1999, Sastry and Lam 2005), where the accumulation isassumed to be known beforehand. This scheme is implemented in NS-2,and the simulation results justify theoretical conclusions. The simulationuses measurements of buffer occupancy, packet arrival, and service ratesat the destination, to determine the source data rates for congestion control.The proposed work appears to provide better results in a wide rangeof networking conditions compared to TCP friendly schemes.3.4.1 Network ModelFigure 3.20 illustrates an end-to-end network configuration for evaluatingthe proposed congestion control schemes. Congestion happens wheneverthe input rate ( Ini)is more than the available link capacity at the ingressnode, or when the network has a congested node inside the network. InFigure 3.20, qk ( ) denotes the network modeled as a single buffer, I r refersto the rate at which packets arrive at the egress node, Uk is the feedbackvariable from the destination, Xd is the desired buffer occupancy at theegress node buffer, S r refers to the departure rate of the packets to thedestination, and Vk is the departure rate of the packets into the networkfrom the ingress node.Most congestion schemes consist of adjusting the input rates to matchthe available link capacity (or rate) (Jain 1996) or carefully admit newtraffic (Qiu 1997, Bae and Suda 1991). Depending upon the duration ofcongestion, different schemes can be applied. For long-term congestion,Ingress nodeIniSVkUkq(k)Feedback (Xk, Ir, Sr)IrEgress nodeSrXd DXkFIGURE 3.20End-to-end network configuration.