Paper Review : Charge-Sensitve TCP and Rate Control in the Internet

Reviewer : Seh Leng Lim

This paper studies the fundamental problem of achieving the system optimum rate in a distributed environment, using only the information available at the end hosts.

The main contribution of the paper is its pricing mechanism proposal that allocates bandwidth fairly and maximizes users’ utility without requiring knowledge of the users’ utility functions and without requiring any explicit feedback from the network. The paper proposes an algorithm that achieves the system optimum at an equilibrium when users update their parameters by solving their own optimization. The algorithm can be deployed over the Internet with minor modifications at the end hosts. This will facilitate the provision of a fair and efficient allocation of the available bandwidth, which is required now especially as the Internet is exploding in size.

The key main ideas expounded are :

(a) achieving maximum total utility of users in a distributed environment, using only information available at the end hosts

(b) the idea of proportional fairness as exemplified by the (p,1)-proportionally fair algorithm which is a window based congestion control mechanism

© users are likely to maximize their own benefit, that is, users are selfish, leading to the use of the noncooperative model to solve the problem

I think that the paper has a significant contribution (rating of 4) to the study of how to implement cost features into the internet, as well as how to control its transmission rate. However, the authors did not explain their rationale behind the utility functions of the various users in their test scenario. Also, the test scenario involves only the simplest one bottleneck dumbbell configuration. Therefore, it is hard to be convinced that their approach will achieve the desired results in the real Internet as claimed.

Researchers and builders working with Internet Service Providers may have a better appreciation from this paper of the difficulties involved in implementing billing mechanisms into the Internet.