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ATM Forum Document Number: ATM Forum/94-0882

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Title: Rate Based Schemes: Mistakes to Avoid

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Abstract:

One key advantage of the rate-based approach in general and the
explicit-rate approach in particular is that it provides
considerable freedom to switch manufacturers in terms of specific
algorithms to use. However, it is easy to misdesign a scheme
unless the overload is measured properly and the feedback is
related to the control properly. This contribution points out
examples of such mistakes.

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Source:

Raj Jain, Shiv Kalyanaraman and Ram Viswanathan
The Ohio State University
Department of CIS
Columbus, OH 43210
Phone: 614-292-3989, Fax: 614-292-2911, Email: Jain@ACM.Org

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Date: September 26-29, 1994

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Distribution: ATM Forum Technical Working Group Members (Traffic Management)

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Notice: This contribution has been prepared to assist the ATM
Forum.  It is offered to the Forum as a basis for discussion and
is not a binding proposal on the part of any of the contributing
organizations.  The statements are subject to change in form and
content after further study.  Specifically, the contributors
reserve the right to add to, amend or modify the statements
contained herein.

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EXTENDED ABSTRACT

The explicit-rate indication that was introduced in the July 1994
ATM Forum meeting [1], has become popular since it allows the
switches considerable freedom in their internal algorithms for
resource allocation and also provides quick indication to the
source about the correct transmission rate.

However, many of the proposals have the following problems:

1. Using queue length as the overload indication
2. Using a single number to indicate rate
3. Providing feedbacks that are not related to the control

In the ATM Forum presentation, we will point out what problems
are caused by these and a few other similar mistakes. In
particular, these result in unnecessary oscillations, large
delays, and unsatisfactory operation with bursty traffic.
Fortunately, it is possible to avoid these mistakes and design
rate based schemes that work perfectly. One such scheme is
described in an accompanying contribution [2].


REFERENCES:

[1] A. Charny, D. Clark, and R. Jain, "Congestion Control with
Explicit Rate Indication," ATM Forum Contribution 94-0692, July
1994.

[2] R. Jain, S. Kalyanraman, R. Viswanathan, "The OSU Scheme for
Congestion Avoidance Using Explicit Rate Indication," ATM Forum
Contribution 94-0883, September 1994.