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Basic Rate Control Mechanism for Broadband Networks

IP.com Disclosure Number: IPCOM000110403D
Original Publication Date: 1992-Nov-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 4 page(s) / 204K

Publishing Venue

IBM

Related People

Doeringer, WA: AUTHOR [+6]

Abstract

Described is a single mechanism for the rate control of data transmission and reception which can be efficiently implemented in hardware to operate at gigabit per second media speeds, and from which all the relevant schemes described in the literature can be readily constructed.

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This is the abbreviated version, containing approximately 47% of the total text.

Basic Rate Control Mechanism for Broadband Networks

       Described is a single mechanism for the rate control of
data transmission and reception which can be efficiently implemented
in hardware to operate at gigabit per second media speeds, and from
which all the relevant schemes described in the literature can be
readily constructed.

      Rate control mechanisms, different as they may seem at first
sight, can all be viewed as credit-based control systems.  The
transmission or reception of one data unit consumes one credit, and
the transmission or reception is only permitted if the credits are
not fully depleted. Any rate control scheme may hence be described by
the initial credit, the algorithm for the calculation of new credits,
and the update times Ti, at which the credit updates are performed.
In order to avoid periodic operations for the novel rate control
scheme, a functionally equivalent but strictly demand-driven approach
was chosen where appropriate (cumulative) credit updates are only
performed at the transmission or reception of a data unit, that is,
at the data unit events.  Thus all rate-control instances that do not
handle a given data unit need not perform any action.  The new credit
is a function of the old credit, the time(s) at which the previous
data unit transmission(s) or reception(s) occurred, and possibly a
few other variables local to the respective rate-control instance.

      This approach is formalized in the subsequent definition of the
basic rate controller using the following notational conventions:
t         the system time, measured in appropriate units.
tcreation the system time at the creation time of the rate control
instance
n         the number of successful data unit events. Initially, n =
0, and at each successful data unit event n is incremented, thus
providing a numbering scheme for units: The i-th successfully
transmitted or received data unit is the data numbered with i.
Ti        a time-stamp that belongs to the i-th successful data unit
event.
Ci        the credit remaining after the i-th successful data unit
event.
Credit Function The Credit Function defines how the new credit is
calculated and how the time-stamps are determined.  That is, it
defines both Cn+1 and Tn+1 as a function of all previous Ti's and
Ci's, with 0 < I < n. Note that most rate-control schemes are
memoryless in that only Cn and Tn are relevant parameters for the
credit function, as shown in the table.

      Each accepted data unit that consumes one credit, and the data
unit will only be accepted if there is enough credit, that is, if the
remaining credit Cn+1 > 0.  The conceptional operation of the novel
general flow control schemes is modelled by the following function,
which returns true if the data unit event being processed is
successful and false otherwise.

                            (Image Omitted)

      The following table summar...