Simplified calculation of cell transmission rates in a cell based netwook
First Claim
1. In a cell based network for transmitting user cells, including data cells and control cells defining an explicit rate, at predetermined cell rates in a forward direction from at least one user source to at least one user destination in a virtual connection through a transmission path including at least one switch and at least one egress transmission link coupled to the switch by an egress physical port, each switch and physical port of each transmission link having limited cell transmission resources and being susceptible to congestion of multiple virtual connections made therethrough, a method of reducing such congestion comprising the steps of:
- establishing a programmed cell rate for each egress physical port coupled to the switch;
upon the arrival of a control cell at the switch, calculating a user source fair share cell transmission rate by;
determining a count of a number of virtual connections through the egress physical port coupled to the switch;
quantizing the count of the number of virtual connections by incrementing the count of the number of virtual connections to a next higher power of two, thereby producing a quantized count; and
determining a fair share cell transmission rate as a function of the programmed cell rate and the quantized count; and
changing the explicit rate in the control cell arriving at the switch to the fair share cell transmission rate.
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0 Petitions
Accused Products
Abstract
A cell based network (100) for transmitting ATM user cells (118), including ABR data cells (118D) and forward control, or RM, cells (118FRM) at predetermined cell rates from at least one user source (102) in a virtual connection (VC, 110) through at least one ATM switch (120) and at least one transmission link (130) in the network to at least one user destination (104), employs a method and apparatus for controlling a user source (102) transmission cell rate in the presence of congestion in the VC (110). The calculation of a Fair Share cell transmission rate is written into a backward control, or RM, cell (118BRM) optionally takes place only in the presence of congestion at an ATM Switch (120). The calculation of the Fair-- Share value is simplified and calculation time is shortened by changing the number of active ABR VCs (NABR) to a factor of two (ENABR) and dividing the maximum cell transmission rate by ENABR.
148 Citations
20 Claims
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1. In a cell based network for transmitting user cells, including data cells and control cells defining an explicit rate, at predetermined cell rates in a forward direction from at least one user source to at least one user destination in a virtual connection through a transmission path including at least one switch and at least one egress transmission link coupled to the switch by an egress physical port, each switch and physical port of each transmission link having limited cell transmission resources and being susceptible to congestion of multiple virtual connections made therethrough, a method of reducing such congestion comprising the steps of:
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establishing a programmed cell rate for each egress physical port coupled to the switch; upon the arrival of a control cell at the switch, calculating a user source fair share cell transmission rate by; determining a count of a number of virtual connections through the egress physical port coupled to the switch; quantizing the count of the number of virtual connections by incrementing the count of the number of virtual connections to a next higher power of two, thereby producing a quantized count; and determining a fair share cell transmission rate as a function of the programmed cell rate and the quantized count; and changing the explicit rate in the control cell arriving at the switch to the fair share cell transmission rate. - View Dependent Claims (2, 3, 4, 5)
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6. In a cell based network for transmitting user cells, including data cells and control cells defining an explicit rate, at predetermined cell rates in a forward direction from at least one user source to at least one user destination in a virtual connection through a transmission path including at least one switch and at least one egress transmission link coupled to the switch by an egress physical port, each switch and physical port of each transmission link having limited cell transmission resources and being susceptible to congestion of multiple virtual connections made therethrough, a method of reducing such congestion comprising the steps of:
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establishing a programmed cell rate for each egress physical port coupled to the switch; determining a count of a number of virtual connections through the egress physical port coupled to the switch, the step of determining comprising; providing an indicia of VC activity in the egress physical port; and altering the indicia of VC activity based on whether a first VC is active; and upon the arrival of a control cell at the switch, calculating a user source fair share cell transmission rate, the step of calculating comprising; quantizing the count of the number of virtual connections by incrementing the count of the number of virtual connections to a next higher power of two thereby producing a quantized count; and determining the fair share cell transmission rate as a function of the programmed cell rate and the quantized count. - View Dependent Claims (7, 8, 9, 10)
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11. In an Asynchronous Transfer Mode (ATM) information network for serially transmitting ATM user cells of ATM traffic categories, including Available Bit Rate (ABR) traffic comprising ABR user data cells and Resource Management (RM) cells having Explicit Rate (ER) fields, each ATM user cell having a defined header with identification data defining a Virtual Connection (VC) from an ATM traffic user source (SES) in a transmission path including one or more ATM switches and interconnecting transmission links having physical ports coupled with the ATM Switches, to an ATM user destination (DES) at an actual cell transmission rate established at the SES, wherein congestion of VCs in a transmission path may occur, a method of controlling such congestion by reducing the actual cell transmission rate of ABR traffic to a Fair Share cell transmission rate comprising the steps of:
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transmitting data and RM cells of ABR traffic from the SES in a forward direction in a VC through the transmission path at the cell transmission rate; at each ATM switch in the transmission path of the VCs in the forward direction, determining whether egress or ingress congestion exists in the ATM switch, and providing an indication of congestion in response thereto; and determining a programmed cell rate of the physical port of the VC having the indication of congestion; sending backward RM cells of ABR traffic in a backward direction from the DES to each ATM switch in the transmission path of each VC; on receipt of a backward RM cell at each ATM switch in the transmission path of the VC, responding to the indication of congestion by; determining a count of the number of VCs through the egress physical port coupled to the ATM Switch; and quantizing the count of the number of VCs to an incremented count of a power of two; determining a Fair Share cell transmission rate as a function of the programmed cell rate of the egress physical port used in the VC and the incremented count; writing the Fair Share cell transmission rate in the ER fields of the backward RM cells; and sending the backward RM cells of the ABR traffic in the backward direction from each such ATM switch in the transmission path of each VC toward the SES; and at the SES, changing the actual cell transmission rate of ABR traffic generated by the SES to the Fair Share cell transmission rate. - View Dependent Claims (12, 13, 14, 15)
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16. In an Asynchronous Transfer Mode (ATM) information network for serially transmitting ATM user cells of ATM traffic categories, including Available Bit Rate (ABR) traffic comprising ABR user data cells and Resource Management (RM) cells having Explicit Rate (ER) fields, each ATM user cell having a defined header with identification data defining a Virtual Connection (VC) from an ATM traffic user source (SES) in a transmission path including one or more ATM switches and interconnecting transmission links having maximum cell transmission rates, to an ATM user destination (DES) at a cell transmission rate established at the SES, wherein congestion of VCs in a transmission path may occur, apparatus for controlling such congestion through controlling the cell transmission rate of ABR traffic to a Fair Share cell transmission rate comprising:
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means for transmitting data and RM cells of ABR traffic from the SES in a forward direction in a VC through the transmission path at the cell transmission rate; at the ATM switch in the transmission path of the VCs in the forward direction, means for determining the presence of congestion of the ATM switch ingress cell memory or of an egress physical port coupled thereto and providing a set indication of congestion in response thereto; means for determining a maximal cell transmission rate of the physical port of the VC having the set indication of congestion; means for sending backward RM cells of ABR traffic in a backward direction from the DES to each ATM switch in the transmission path of each VC; at the ATM switch in the transmission path of the VCs in the backward direction, means operable on receipt of a backward RM cell at each ATM switch in the transmission path of the VC including; means for determining a count of the number of VCs through the egress physical port coupled to the ATM Switch; and means for changing the count of the actual number of VCs to a changed count of a power of two; means for determining a Fair share cell transmission rate as a function of the maximum cell transmission rate of the egress physical port used in the VC and the changed count; means for writing the Fair Share cell transmission rate in the ER fields of the backward RM cells; and means for sending the backward RM cells of the ABR traffic in the backward direction from each such ATM switch in the transmission path of each VC toward the SES; and at the SES, means for changing the actual cell transmission rate of ABR traffic generated by the SES to the Fair Share cell transmission rate in the ER field of the backward RM cells. - View Dependent Claims (17, 18, 19, 20)
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Specification