Medium and system for controlling atm traffic using bandwidth allocation technology

Abstract

A medium and system for managing asynchronous transfer mode (ATM) traffic in a computer system is disclosed. The computer system is used in sending, receiving, or sending and receiving a plurality of ATM flows. Each ATM flow has a plurality of ATM cells, a minimum ATM bandwidth guarantee, and a maximum ATM bandwidth. The medium and system include determining whether excess bandwidth exists for the ATM flows. The method and system also include gracefully increasing a portion of the ATM cells transmitted for each ATM flow during periods of excess bandwidth. The portion of the ATM cells transmitted is not more than the maximum ATM bandwidth limit. If an ATM flow presents a sufficient offered load, the portion of the ATM cells transmitted in the flow is not less than a minimum ATM bandwidth guarantee.

1 . A computer-readable medium encoded with a computer program for managing asynchronous transfer mode (ATM) traffic in a plurality of ATM flows, the computer program comprising executable instructions for: determining whether any of the plurality of ATM flows has excess bandwidth, each ATM flow having an ATM cell flow rate, a minimum ATM bandwidth guarantee, and a maximum ATM bandwidth limit; and responsive to one or more ATM flows having excess bandwidth, gradually increasing the ATM cell flow rate of each ATM flow having excessive bandwidth without exceeding the maximum ATM bandwidth limit of each ATM flow having excess bandwidth, and provided a sufficient load is offered, without falling below the minimum ATM bandwidth guarantee of each ATM flow having excess bandwidth 
     
     
         2 . The computer-readable medium of  claim 1 , wherein transmission of ATM cells in each ATM flow is based on a transmit fraction of the ATM flow such that an ATM cell is transmitted in each ATM flow only when the transmit fraction of the ATM flow is greater than or equal to a generated random number, the transmit fraction being between zero and one, and gradually increasing the ATM cell flow rate of each ATM flow having excess bandwidth comprises:linearly increasing the transmit fraction of each ATM flow having excess bandwidth towards one. 
     
     
         3 . The computer-readable medium of  claim 2 , wherein determining whether any of the plurality of ATM flows has excess bandwidth comprises determining whether any of the plurality of ATM flows has excess bandwidth in a current refresh period, providing an excess bandwidth signal for the current refresh period, the excess bandwidth signal being one when excess bandwidth exists and zero when excess bandwidth is not available, and providing an average excess bandwidth signal for the current refresh period, the average excess bandwidth signal being an exponentially weighted moving average of the excess bandwidth signal, and linearly increasing the transmit fraction of each ATM flow having excess bandwidth comprises selecting a constant for each ATM flow having excess bandwidth, calculating a product for each ATM flow having excess bandwidth by multiplying the constant selected for the ATM flow by the average excess bandwidth signal, and calculating a transmit fraction of each ATM flow having excess bandwidth for the current refresh period by adding the product calculated for the ATM flow to a transmit fraction of the ATM flow for a previous refresh period. 
     
     
         4 . The computer-readable medium of  claim 3 , wherein selecting the constant for each ATM flow having excess bandwidth comprises: selecting the constant for each ATM flow having excess bandwidth based on a priority of the ATM flow. 
     
     
         5 . The computer-readable medium of  claim 1 , wherein the computer program further comprises executable instructions for: responsive to no ATM flow having excess bandwidth, gradually decreasing the ATM cell flow rate of each ATM flow. 
     
     
         6 . The computer-readable medium of  claim 5 , wherein transmission of ATM cells in each ATM flow is based on a transmit fraction of the ATM flow such that an ATM cell is transmitted in each ATM flow only when the transmit fraction of the ATM flow is greater than or equal to a generated random number the transmit fraction being between zero and one, and gradually decreasing the ATM cell flow rate of each ATM flow comprises: exponentially decreasing the transmit fraction of each ATM flow towards zero. 
     
     
         7 . The computer-readable medium of  claim 6 , wherein determining whether any of the plurality of ATM flows has excess bandwidth comprises determining whether any of the plurality of ATM flows has excess bandwidth in a current refresh period, and exponentially decreasing the transmit fraction of each ATM flow comprises selecting a constant for each ATM flow, calculating a transmitted flow rate for each ATM flow by dividing a rate of ATM cell transmission observed for the ATM flow by a maximum rate of ATM cell transmission obtainable by any of the plurality of ATM flows, calculating a product for each ATM flow by multiplying the constant selected for the ATM flow by the transmitted flow rate calculated for the ATM flow, and calculating a transmit fraction of each ATM flow for the current refresh period by subtracting the product calculated for the ATM flow from a transmit fraction of the ATM flow for a previous refresh period. 
     
     
         8 . The computer-readable medium of  claim 7 , wherein selecting the constant for each ATM flow comprises: selecting the constant for each ATM flow based on a priority of the ATM flow. 
     
     
         9 . A system for managing asynchronous transfer mode (ATM) traffic in a plurality of ATM flows, the system comprising: at least one queue storing ATM cells to be transmitted; and a flow control mechanism in communication with the at least one queue, the flow control mechanism determining whether any of the plurality of ATM flows has excess bandwidth, each ATM flow having an ATM cell flow rate, a minimum ATM bandwidth guarantee, and a maximum ATM bandwidth limit; and responsive to one or more ATM flows having excess bandwidth, gradually increasing the ATM cell flow rate of each ATM flow having excessive bandwidth without exceeding the maximum ATM bandwidth limit of each ATM flow having excess bandwidth, and provided a sufficient load is offered, without failing below the minimum ATM bandwidth guarantee of each ATM flow having excess bandwidth. 
     
     
         10 . The system of  claim 9 , wherein transmission of ATM cells in each ATM flow is based on a transmit fraction of the ATM flow such that an ATM cell is transmitted in each ATM flow only when the transmit fraction of the ATM flow is greater than or equal to a generated random number, the transmit fraction being between zero and one, and gradually increasing the ATM cell flow rate of each ATM flow having excess bandwidth comprises: linearly increasing the transmit fraction of each ATM flow having excess bandwidth towards one. 
     
     
         11 . The system of  claim 10 , wherein determining whether any of the plurality of ATM flows has excess bandwidth comprises determining whether any of the plurality of ATM flows has excess bandwidth in a current refresh period, providing an excess bandwidth signal for the current refresh period, the excess bandwidth signal being one when excess bandwidth exists and zero when excess bandwidth is not available, and providing an average excess bandwidth signal for the current refresh period, the average excess bandwidth signal being an exponentially weighted moving average of the excess bandwidth signal, and linearly increasing the transmit fraction of each ATM flow having excess bandwidth comprises selecting a constant for each ATM flow having excess bandwidth, calculating a product for each ATM flow having excess bandwidth by multiplying the constant selected for the ATM flow by the average excess bandwidth signal, and calculating a transmit fraction of each ATM flow having excess bandwidth for the current refresh period by adding the product calculated for the ATM flow to a transmit Fraction of the ATM flow for a previous refresh period. 
     
     
         12 . The system of  claim 11 , wherein selecting the constant for each ATM flow having excess bandwidth comprises: selecting the constant for each ATM flow having excess bandwidth based on a priority of the ATM flow. 
     
     
         13 . The system of  claim 9 , wherein the flow control mechanism further responsive to no ATM flow having excess bandwidth, gradually decreases the ATM cell flow rate of each ATM flow. 
     
     
         14 . he system of  claim 13 , wherein transmission of ATM cells in each ATM flow is based on a transmit fraction of the ATM flow such that an ATM cell is transmitted in each ATM flow only when the transmit fraction of the ATM flow is greater than or equal to a generated random number, the transmit fraction being between zero and one, and gradually decreasing the ATM cell flow rate of each ATM flow comprises: exponentially decreasing the transmit fraction of each ATM flow towards zero. 
     
     
         15 . The system of  claim 14 , wherein determining whether any of the plurality of ATM flows has excess bandwidth comprises determining whether any of the plurality of ATM flows has excess bandwidth in a current refresh period, and exponentially decreasing the transmit fraction of each ATM flow comprises selecting a constant for each ATM flow, calculating a transmitted flow rate for each ATM flow by dividing a rate of ATM cell transmission observed for the ATM flow by a maximum rate of ATM cell transmission obtainable by any of the plurality of ATM flows, calculating a product for each ATM flow by multiplying the constant selected for the ATM flow by the transmitted flow rate calculated for the ATM flow, and calculating a transmit fraction of each ATM flow for the current refresh period by subtracting the product calculated for the ATM flow from a transmit fraction of the ATM flow for a previous refresh period. 
     
     
         16 . The system of  claim 15 , wherein selecting the constant for each ATM flow comprises: selecting the constant for each ATM flow based on a priority of the ATM flow.