Exploiting Chemistry for Better Packet Flow Management 5: Chemical Congestion Control, Design Motifs, and Conclusion
This represents the final installment of the series reviewing the 2011 technical report by Meyer and Tschudin. Part 1 gave an overview of the report and the problems it aimed to solve, as well as the chemistry basics necessary for further understanding. Part 2 discussed artificial chemistries and the extension to an artificial packet chemistry, setting the mathematical framework for analyses and implementation. Part 3 discussed briefly some methods of network analysis available once the artificial packet chemistry was developed. Part 4 gave an implementation of a scheduler based on the packet chemistry model as well as the idea of a chemical control plane and its implementation. This final part will discuss one final application — a congestion control algorithm–as well as mention design motifs pointed out by the authors and conclude our analysis of this report.
Chemical Congestion Control Algorithm
- Arriving packets are put into a queue D. The transmission rate \nu_{tx} is controlled by the quantity of pacemaker molecules R, so \nu_{tx} = k_{1}c_{R}c_{D}, once again according to the Law of Mass Action. To mimic the additive (linear) increase mechanism of TCP-Reno, the number of pace-maker molecules is increased at a rate \nu_{\text{inc}}.
- Before packets are transmitted, they are tagged with a sequence number. If there is a gap in the sequence number of acknowledgments from the destination, the source regenerates the packets at a queue L.
- A lost packet will catalyze the destruction of pacemaker molecules by another reaction r_{2}, which will lead to the exponential decay of R-molecules and thus decrease the transmission rate. However, we wish to prevent too fast a destruction of pacemaker molecules, so a third reaction r_{3} will delay the destruction.
Design Motifs
Conclusion
References
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