Paper review: < Charge-Sensitive TCP and Rate Control in the Internet [LA00] >

Reviewer: <Ryan Gehl>

1. State the problem the paper is trying to solve.

The purpose of this paper is to investigate the problem of achieving optimal rates in a distributed environment using only the information available at the end hosts.

2. State the main contribution of the paper: solving a new problem, proposing a new algorithm, or presenting a new evaluation (analysis). If a new problem, why was the problem important? Is the problem still important today? Will the problem be important tomorrow?  If a new algorithm or new evaluation (analysis), what are the improvements over previous algorithms or evaluations? How do they come up with the new algorithm or evaluation? 

The main contribution of this paper is that a user-centric optimization algorithm, which does not require any explicit network feeback and is therefore able to be deployed on the Internet, achieves the system optimum at equilibrium.

3. Summarize the (at most) 3 key main ideas (each in 1 sentence.) 

(1) While fairness is a desirable property to have, fairness alone may not be a good objective. The available bandwidtch should also be allocated in such a way that the overall utility of the users is maximized.
(2) The authors' proposed algorithm can be implemented over the current Internet (without extensive modifications inside the network) by a simple modification of the existing TCP at the end hosts.

4. Critique the main contribution
   • Rate the significance of the paper on a scale of 5 (breakthrough), 4 (significant contribution), 3 (modest contribution), 2 (incremental contribution), 1 (no contribution or negative contribution). Explain your rating in a sentence or two.

   I would rate this paper as a 4 because this paper does present a deployable algorithm which is a slight modification to TCP at the end host. As the authors mentioned in the paper, their work is really a natural extension of previous work by other authors.

   • Rate how convincing the methodology is: how do the authors justify the solution approach or evaluation? Do the authors use arguments, analyses, experiments, simulations, or a combination of them? Do the claims and conclusions follow from the arguments, analyses or experiments? Are the assumptions realistic (at the time of the research)? Are the assumptions still valid today? Are the experiments well designed? Are there different experiments that would be more convincing? Are there other alternatives the authors should have considered? (And, of course, is the paper free of methodological errors.)

   To justify their results, the authors addressed the problem in a mathematical setting by providing proofs of network performance under given assumptions. In terms of actually showing that this idea worked in practice, the authors only provided a "numerical example," which makes it seems as if their approach may not be as deployable as they claim. (Otherwise, why wouldn't they have implemented it instead of just giving us one simulation example).

   • What is the most important limitation of the approach?

   One limitation of their approach is I'm not convinced of the effective deployability of their algorithm. (How does it work if not everyone in the network has their modification?)

5. What lessons should researchers and builders take away from this work. What (if any) questions does this work leave open?

One lesson researchs should take away from this work is that network equilibrium can/should be achieved through local user optimization of some pricing function as opposed to attempting implement a central authority within the network.