Method and apparatus for auto detection of aal5 type frames
OwnerBernard St-Denis, John Pillar +1inventors
InventorsBERNARD ST-DENIS, JOHN PILLAR, BERNARD MARCHAND
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Abstract
In Asynchronous Transfer Mode (ATM) communications networks, certain congestion control features, such as Partial Packet Discard (PPD) and Early Packet Discard (EPD), operate on ATM cells that have been segmented from ATM Adaptation Layer #5 (AAL5) frames (packets). AAL5 frames are automatically detected by observing transitions of an indicator in the ATM cell header unique to AAL5 traffic. Automatic detection of AAL5 traffic allows enablement of packet discard techniques such as PPD and EPD.
Claims16
A method for determining whether user data cells passing through an ATM switch carry data that has been segmented using AAL5, each user data cell containing a bit having at least two states which indicate cell type when AAL5 is being used, the method comprising the steps of:
- monitoring the state of the bit in each cell;
- and
- identifying the cells as carrying data that has been segmented using AAL5 when the state of the bit transitions from a first value to a second value.
A method for determining whether user data cells passing through an ATM switch belong to a class of cells, each cell containing a bit having at least two states which indicate cell type, the method comprising the steps of:
- monitoring the state of the bit in each cell;
- and
- identifying the cells as belonging to the class when the state of the bit transitions from a first value to a second value.
A method for controlling congestion of cells in an ATM switch using a packet discard feature, the method comprising the steps of:
- determining whether user data cells passing through the switch carry data that has been segmented using AAL5;
- and
- enabling the packet discard feature if the user data cells carry data that has been segmented using AAL5.
A method for controlling congestion of cells on a connection in an ATM switch using a packet discard feature, each cell containing a bit having at least two states which indicate cell type when AAL5 is being used, the method comprising the steps of:
- conditionally enabling the packet discard feature if the cell type is unknown at the time the connection is established;
- monitoring the state of the bit in each cell received at the switch;
- and
- enabling the packet discard feature if the feature has been conditionally enabled and the switch receives a cell with a bit in a first state followed by a cell with a bit in a second state.
An apparatus for determining whether user data cells passing through an ATM switch carry data that has been segmented using AAL5, each user data cell containing a bit having at least two states which indicate cell type when AAL5 is being used, the apparatus comprising:
- means for monitoring the state of the bit in each user data cell;
- and
- means for identifying the cells as carrying data that has been segmented using AAL5 when the state of the bit transitions from a first value to a second value.
An apparatus for determining whether user data cells passing through an ATM switch belong to a class of cells, each cell containing a bit having at least two states which indicate cell type, the apparatus comprising:
- means for monitoring the state of the bit in each cell;
- and
- means for identifying the cells as belonging to the class when the state of the bit transitions from a first value to a second value.
An apparatus for controlling congestion of cells in an ATM switch using a packet discard feature, the apparatus comprising:
- means for determining whether user data cells passing through the switch carry data that has been segmented using AAL5;
- and
- means for enabling the packet discard feature if the user data cells carry data that has been segmented using AAL5.
An apparatus for controlling congestion of cells on a connection in an ATM switch using a packet discard feature, each cell containing a bit having at least two states which indicate cell type when AAL5 is being used, the apparatus comprising:
- means for conditionally enabling the packet discard feature if the cell type is unknown at the time the connection is established;
- means for monitoring the state of the bit in each cell received at the switch;
- and
- means for enabling the packet discard feature if the feature has been conditionally enabled and the switch receives a cell with a bit in a first state followed by a cell with a bit in a second state.
A communications network comprising:
- a plurality of nodes sending and receiving ATM cells;
- and
- an ATM switch interconnecting the nodes, the switch including
- means for determining whether user data cells passing through the switch carry data that has been segmented using AAL5;
- and
- means for enabling a packet discard feature if the user data cells carry data that has been segmented using AAL5.
A communications network comprising:
- a plurality of nodes sending and receiving ATM cells, each cell containing a bit having at least two states which indicate cell type when AAL5 is being used;
- and
- an ATM switch interconnecting the nodes, the switch including
- means for monitoring the state of the bit in each cell;
- and
- means for identifying the cells as carrying data that has been segmented using AAL5 when the state of the bit transitions from a first value to a second value.
Dependencies are inferred from the claim text.