Method and apparatus for auto detection of AAL5 type frames for VCC and VPC switches
AssigneeCiena Corporation
InventorsJohn Frank Pillar, Bernard St. Denis, Bernard Marchand
Life of this patent
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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-aware cell discarding techniques such as PPD and EPD on a Virtual Channel Connection (VCC) basis, whether in a switch for a VCC or for a Virtual Path Connection (VPC) to which the VCC belongs.
Claims21
A method for determining whether user data cells passing through a switch belong to a class of cells, each cell including data having at least two states, the method comprising:
- monitoring the state of the data in each cell;
- identifying a change in the state of the data from a first cell to a subsequent cell;
- identifying the cells as belonging to the class when the state of the data transitions from a first value to a second value;
- and
- in response to identifying the cells as belonging to the class, enabling a feature for the cells that applies to cells belonging to the class and not to cells belonging to a different class.
A method for controlling the congestion of cells on a path comprising at least one channel in a switch using a packet-aware cell discarding feature, each cell including data having at least two states, the method comprising:
- learning of an existence of active channels within the path by monitoring headers of cells;
- monitoring the state of the data in each cell received at the switch;
- identifying a change in the state of the data from a first cell to a subsequent cell;
- and
- enabling the packet-aware cell discarding feature for an active channel if the switch receives a cell associated with the active channel with the data in a predetermined one of the two states.
A communications network comprising:
- a switch interconnecting a plurality of nodes sending and receiving cells, each cell including data having at least two states, the switch including:
- means for monitoring a state of the data in each cell;
- means for identifying a change in the state of the data from a first cell to a subsequent cell;
- means for identifying associated cells as belonging to a class of cells when the state of the data transitions from a first value to a second value;
- and
- means for enabling, in response to identifying the associated cells as belonging to the class, a feature for the associated cells that applies to cells belonging to the class and not to cells belonging to a different class.
Dependencies are inferred from the claim text.