**Paper Review
: Analysis of the Increase and Decrease Algorithms for Congestion
Avoidance in Computer Networks**

**Reviewer :**** Seh Leng Lim**

With congestion avoidance mechanisms, a network can
operate in the optimal region of low delay and high throughput (that is at the
knee of its throughput/load curve), thereby avoiding being congested. The paper
focuses on first-order increase/decrease algorithms for congestion avoidance,
using metrics such as efficiency, fairness, convergence time, and size of
oscillation to compare them. By comparison, the authors are able to identify
the sort of increase/decrease congestion algorithm that will help the network
settle to an efficient and fair state regardless of its starting state.

The main contribution of the paper is its proposal
that for optimal convergence to efficiency and feasibility, the increase policy
should be additive and the decrease policy should be multiplicative. It does so
by gently walking the reader through the relevant first order equations using
the criterion of efficiency, fairness, distributedness
and convergence.

The key main ideas expounded are:

(a) The
binary feedback scheme whereby to keep the network operating in the optimal
region of low delay and high throughput, the network monitors its load level
and uses a bit in the network packet header to ask the users to increase or
decrease the load as appropriate.

(b) An additive increase with
multiplicative decrease window sizing policy will help to produce optimal
convergence to fairness

I think that the paper has a significant
contribution (rating of 4) to the study of congestion
avoidance mechanisms in the computer networks. The paper does have an
interesting approach to its comparison of the collision avoidance mechanisms
with the use of algebraic mathematics. Logically and theoretically, the
propositions in the paper are convincing. However, there is no experimental data
to backup the claims except for the announcement that this will be implemented
in the Digital Networking Architecture and OSI Transport Class 4 Networks. Nevertheless,
it is still a very interesting and stimulating paper to read.

The authors have identified a few to be explored
areas such as the impact of delayed feedback on control (since the authors have
assumed that the feedback is synchronous for all users), the marginal utility
of increased bits of feedback and the benefits of guessing the current number
of users.

Researchers and builders who build TCP/IP stacks,
routers or even internet applications will have a better feel of the limitations
in implementing network congestion avoidance mechanisms from this paper.