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       ATM Forum Document Number: ATM Forum/95-0809

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       Title: Examples of Switch Mechanisms - Corrected Text for the Appendix

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       Abstract: The example switch scheme in the appendix inadvertantly
       describes the older time based scheme. It should be replaced by
       its newer version (ERICA) which is count-based and is compatible
       with current source requirements. This contribution provides the
       replacement text.

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       Source:

       Raj Jain, Shiv Kalyanaraman, and Rohit Goyal
       The Ohio State University, Department of CIS, Columbus, OH 43210-1277
       Phone: 614-292-3989, Fax: 614-292-2911, Email: Jain@ACM.Org

       Vijay K. Samalam
       GTE Laboratories Inc, 40 Sylvan Road, Waltham, MA 02254, Email: vks@gte.ecom

       The presentation of this contribution at the ATM Forum is sponsored by
       NIST.

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       Date: June 5-9, 1995, Orlando

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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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       The appendix section 5.7 in the current draft version of the
       traffic management document gives a high level description of the
       switch mechanisms.  While the contributors of that section meant
       to describe the Explicit Rate Indication for Congestion Avoidance
       (ERICA) as one of the congestin avoidance mechanisms. He
       inadvertantly refered to its older version known as OSU scheme,
       which was time based. The current version ERICA is count based,
       is compatible with the current source requirements and,
       therefore, is the correct one to be included. We propose that the
       subsection entitled "Time-based Congestion Avoidance" be replaced
       as follows: [Motion]

       Explicit Rate Indication For Congestion Avoidance (ERICA)

       ERICA [9] tries to maintaion the network at a load z close to
       one.  For this purpose it calculates two quantities fairshare and
       this VC's share:
               Fairshare = Target capacity/Number of active VCs
                               VCshare = CCR / z

       Here CCR is the current cell rate declared by the source in the
       RM cell (or as measured by the switch).  This scheme acheives
       fairness concurrently with efficiency by using the following
       formula to compute the explicity rate (ER):
                         ER = Max (Fairshare, VCshare)

       The above quantities are measured periodically using information
       from the forward going RM cells, and the feedback is given in the
       backward going RM cells. This ensures that the most current
       information is used to provide fastest feedback. The measurement
       interval is independent of the rate at which the sources send RM
       cells. For each interval, no more than one new explicit rate
       value is advertised per VC.  This avoids conflicting feedback to
       sources due to stale information at the switches.  The scheme has
       few parameters which can be easily tuned. There are a few other
       variations of this scheme [10].

       [9] R. Jain, S. Kalyanaraman, R. Viswanathan, and R. Goyal, ``A
       Sample Switch Algorithm,''  AF-TM 95-0178R1, February 1995.

       [10] R. Jain, S. Kalyanaraman, R. Goyal, ``Simulation Results for
       ERICA Switch Algorithm with VBR+ABR Traffic,'' ATM Forum/95-0467,
       April 1995.