Presenter: Keith Winstein
Introduction/Motivation
The talk was about the new approach to control end-to-end
congestion on a multi-user network. The main motivation behind the system built
by the authors “is it possible for a computer to discover the right rules for
congestion control in heterogeneous and dynamic networks? Should computers,
rather than humans, be tasked with congestion control methods? And how well can
computers perform this task?”
System
They presented the system “Remy”, a program that generates
congestion control schemes offline.
Input to the system:
1. Prior assumptions depicting what the networks
may do.
2. Goal to highlight what applications want.
Output: CC algorithm for a TCP sender (RemyCC)
Time: A few hours
Cost: $5-$10 on Amazon EC2
Remy searches for the best congestion-control algorithm,
optimizes expected objective over prior assumptions and makes tractable by
limiting available state. Remy finds the
piecewise-continuous RULE() that optimizes expected value of objective
function.
Evaluation
The authors have done the evaluation of their system in ns-2
and have compared the results with end-to-end (NewReno, Cubic, Compound and Vegas)
and in-network solutions (Cubic-over-sfqCoDel, XCP). The evaluation results showed that with Remy
algorithm one can achieve maximum throughput and least queuing latency for
fixed rate networks. But the algorithm is not so good for variable rate networks.
Conclusion
Remy provides complex rules with consistent behavior as
compared to simple rules and complex behavior in case of traditional policies.
Computer-designed and end-to-end solution is better than human-designed and
in-network congestion control solutions.
Q: Kelly also
solves this problem. So how is your system different than it?
Ans: Remy is
targeted for dynamic case real
networks
Q: Why were you
surprised that your(computer generated) scheme is better? [Unable to understand
the complete question clearly]
Ans: I am not
surprised that computer generated end-to-end scheme can beat the in-network
end-to-end scheme. I am surprised that end-to-end scheme can beat the
in-network schemes. I didn’t imagine that how computer-generated schemes can
outperform XCP.
Q: What about
heterogeneous systems with different RemyCC vs TCP?
Ans: We did talk
about it in a paper with RemyCC vs existing TCP.
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