1. Design of an optimal AQM controller for the Diffserv architecture Leonardo Rangel / Nelson Fonseca Institute of Computing - IC Unicamp, Campinas, 13086-970, SP, Brazil {leonardo.rangel,nfonseca}@ic.unicamp.br

2. Congestion Control System Diffserv: Differentiated Services over the Internet Integrated Congestion Control System ● TCP congestion control mechanism can dynamically adjust the amount of data that a client sends to network; ● AQM mechanisms monitor the queue state at the routers, therefore can detect incipient congestion; ● Integrated TCP/AQM Congestion Control System:  AQM role: early notification of incipient congestion to TCP senders;  When notified about the incipient congestion, TCP senders can decrease their transmission rates before queue overflows.

3. TCP/AQM viewed as a feedback control system: ● The congestion level (router queue size - q) is determined by TCP transmission rate, which is regulated by drop/mark levels; ● An appropriate mark/drop probability (p) is calculated by AQM controller, C(s); ● The proposed controller also stabilizes the system plant, P(s), minimize jitter and give users a certain minimum guaranteed transmission rate. The feedback control system P(s) C(s) q q0q0 + δpδp p - δqδq p0p0 A basic feedback control system

4. Current status What we already done: ● Modeling of TCP flows and AQM routers behavior; ● Investigation of the system's best equilibrium point; ● Controller synthesis using Optimization and Control Theory; ● Implementation of the TCP/AQM system in a continuous-time environment (Simulink/Matlab); ● Controller discretization; ● Implementation of the controller in a discrete-time dynamic network environment (NS-2). Next steps: ● Define representative NS-2 simulation scenarios; ● Simulation and comparison with current proposals.