design of an optimal aqm controller for the diffserv architecture leonardo rangel / nelson fonseca...
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Design of an optimal AQM controller for the Diffserv
architecture
Design of an optimal AQM controller for the Diffserv
architecture
Leonardo Rangel / Nelson FonsecaInstitute of Computing - IC
Unicamp, Campinas, 13086-970, SP, Brazil{leonardo.rangel,nfonseca}@ic.unicamp.br
Congestion Control SystemCongestion 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.
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 systemThe feedback control system
P(s)
C(s)
q
q0
+
δp
p
-δq
p0
A basic feedback control system
Current statusCurrent 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.