Traffic shaping system with transmit latency feedback for asynchronous transfer mode networks
First Claim
1. A method for controlling the transmission of cells from a network node, comprising the steps of:
- periodically scanning a table, said table having one or more entries, each one of said entries corresponding to a virtual circuit connected with said network node, said step of scanning including incrementing a first accumulator, a second accumulator and a third accumulator in each one of said table entries, said third accumulator value reflecting the time since the last transmission on said virtual circuit corresponding with said one of said table entries, and setting a transmit enable bit in each said table entry having a first accumulator value greater than or equal to a first predetermined value and having a second accumulator value greater than or equal to a second predetermined value;
selecting, responsive to said step of scanning, one of said table entries having said transmit enable bit set and having a third accumulator value equal to or greater than the third accumulator value of any other table entry having said transmit enable bit set; and
transmitting, responsive to said step of selecting, a cell on a virtual circuit associated with said selected one of said table entries.
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Abstract
A system for controlling the transmission of cells from a network node over multiple Virtual Circuits (VCs) is disclosed. The system performs traffic shaping, as required by connection based systems such as Asynchronous Transfer Mode (ATM), for each VC connected with a network node, so that the Quality of Service (Qos) parameters established when the connection was established are not exceeded. The system includes a process for scheduling the transmission of cells from the network node. The scheduling process periodically scans a table having entries corresponding to virtual circuits connected with the network node. During each scan of the table, the scheduler increments a sustainable rate accumulator field, a peak rate accumulator field, and a latency accumulator field of each table entry that corresponds with a virtual circuit that is open, and for which there is a cell ready to be transmitted. The scheduler further determines if the sustainable rate accumulator value is greater than or equal to a predetermined value and whether the peak rate accumulator value is greater than or equal to a predetermined value. If both conditions are true, then a cell may be transmitted on the virtual circuit corresponding with that table entry. The system further provides that transmissions are scheduled on virtual circuits having the greatest latency since previous transmissions.
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Citations
15 Claims
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1. A method for controlling the transmission of cells from a network node, comprising the steps of:
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periodically scanning a table, said table having one or more entries, each one of said entries corresponding to a virtual circuit connected with said network node, said step of scanning including incrementing a first accumulator, a second accumulator and a third accumulator in each one of said table entries, said third accumulator value reflecting the time since the last transmission on said virtual circuit corresponding with said one of said table entries, and setting a transmit enable bit in each said table entry having a first accumulator value greater than or equal to a first predetermined value and having a second accumulator value greater than or equal to a second predetermined value; selecting, responsive to said step of scanning, one of said table entries having said transmit enable bit set and having a third accumulator value equal to or greater than the third accumulator value of any other table entry having said transmit enable bit set; and
transmitting, responsive to said step of selecting, a cell on a virtual circuit associated with said selected one of said table entries.
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2. A system for controlling the transmission of cells from a network node, comprising:
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a scheduling table having one or more entries, each entry indicating a virtual circuit and having a first rate accumulator field, a second rate accumulator field, a latency accumulator field, a first predetermined value, a second predetermined value and a latency increment field; means for periodically scanning each said scheduling table entry every time period T, said scanning including incrementing said first rate accumulator field and said second rate accumulator field and adding the value of said latency increment field to said latency accumulator field; means, responsive to said means for periodically scanning, for selecting one of said one or more scheduling table entries having said first rate accumulator field value greater than or equal to said first predetermined value and said second rate accumulator field value greater than or equal to said second predetermined value and having a latency accumulator field value greater than or equal to said latency accumulator field value of any other of said one or more scheduling table entries also having said first rate accumulator field value greater than or equal to said first predetermined value and said second rate accumulator field value greater than or equal to said second predetermined value; and means, responsive to said means for selecting, for transmitting a cell on a virtual circuit indicated by said selected one of said one or more scheduling table entries. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification