Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/18—End to end
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F15/00—Digital computers in general; Data processing equipment in general
  • G06F15/16—Combinations of two or more digital computers each having at least an arithmetic unit, a program unit and a register, e.g. for a simultaneous processing of several programs
  • G06F15/163—Interprocessor communication
  • G06F15/173—Interprocessor communication using an interconnection network, e.g. matrix, shuffle, pyramid, star, snowflake
  • G06F15/17356—Indirect interconnection networks
  • G06F15/17368—Indirect interconnection networks non hierarchical topologies
  • G06F15/17375—One dimensional, e.g. linear array, ring
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/46—Interconnection of networks
  • H04L12/4604—LAN interconnection over a backbone network, e.g. Internet, Frame Relay
  • H04L12/4608—LAN interconnection over ATM networks
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/54—Store-and-forward switching systems 
  • H04L12/56—Packet switching systems
  • H04L12/5601—Transfer mode dependent, e.g. ATM
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/54—Store-and-forward switching systems 
  • H04L12/56—Packet switching systems
  • H04L12/5601—Transfer mode dependent, e.g. ATM
  • H04L12/5602—Bandwidth control in ATM Networks, e.g. leaky bucket
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/11—Identifying congestion
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/26—Flow control; Congestion control using explicit feedback to the source, e.g. choke packets
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/26—Flow control; Congestion control using explicit feedback to the source, e.g. choke packets
  • H04L47/266—Stopping or restarting the source, e.g. X-on or X-off
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/29—Flow control; Congestion control using a combination of thresholds
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/30—Flow control; Congestion control in combination with information about buffer occupancy at either end or at transit nodes
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/50—Queue scheduling
  • H04L47/62—Queue scheduling characterised by scheduling criteria
  • H04L47/621—Individual queue per connection or flow, e.g. per VC
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/10—Packet switching elements characterised by the switching fabric construction
  • H04L49/104—Asynchronous transfer mode [ATM] switching fabrics
  • H04L49/105—ATM switching elements
  • H04L49/106—ATM switching elements using space switching, e.g. crossbar or matrix
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/10—Packet switching elements characterised by the switching fabric construction
  • H04L49/104—Asynchronous transfer mode [ATM] switching fabrics
  • H04L49/105—ATM switching elements
  • H04L49/107—ATM switching elements using shared medium
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/15—Interconnection of switching modules
  • H04L49/1515—Non-blocking multistage, e.g. Clos
  • H04L49/153—ATM switching fabrics having parallel switch planes
• • H—ELECTRICITY
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  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/15—Interconnection of switching modules
  • H04L49/1553—Interconnection of ATM switching modules, e.g. ATM switching fabrics
• • H—ELECTRICITY
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  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/15—Interconnection of switching modules
  • H04L49/1553—Interconnection of ATM switching modules, e.g. ATM switching fabrics
  • H04L49/1576—Crossbar or matrix
• • H—ELECTRICITY
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  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/20—Support for services
  • H04L49/201—Multicast operation; Broadcast operation
  • H04L49/203—ATM switching fabrics with multicast or broadcast capabilities
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/25—Routing or path finding in a switch fabric
  • H04L49/253—Routing or path finding in a switch fabric using establishment or release of connections between ports
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/25—Routing or path finding in a switch fabric
  • H04L49/253—Routing or path finding in a switch fabric using establishment or release of connections between ports
  • H04L49/255—Control mechanisms for ATM switching fabrics
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/25—Routing or path finding in a switch fabric
  • H04L49/256—Routing or path finding in ATM switching fabrics
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/30—Peripheral units, e.g. input or output ports
  • H04L49/3081—ATM peripheral units, e.g. policing, insertion or extraction
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/30—Peripheral units, e.g. input or output ports
  • H04L49/3081—ATM peripheral units, e.g. policing, insertion or extraction
  • H04L49/309—Header conversion, routing tables or routing tags
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/45—Arrangements for providing or supporting expansion
  • H04L49/455—Provisions for supporting expansion in ATM switches
• • H—ELECTRICITY
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  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L49/00—Packet switching elements
  • H04L49/55—Prevention, detection or correction of errors
  • H04L49/552—Prevention, detection or correction of errors by ensuring the integrity of packets received through redundant connections
• • H—ELECTRICITY
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  • H04L49/00—Packet switching elements
  • H04L49/55—Prevention, detection or correction of errors
  • H04L49/555—Error detection
• • H—ELECTRICITY
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  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
  • H04L69/30—Definitions, standards or architectural aspects of layered protocol stacks
  • H04L69/32—Architecture of open systems interconnection [OSI] 7-layer type protocol stacks, e.g. the interfaces between the data link level and the physical level
  • H04L69/322—Intralayer communication protocols among peer entities or protocol data unit [PDU] definitions
  • H04L69/324—Intralayer communication protocols among peer entities or protocol data unit [PDU] definitions in the data link layer [OSI layer 2], e.g. HDLC
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q11/00—Selecting arrangements for multiplex systems
  • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
  • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
  • H04Q11/0478—Provisions for broadband connections
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/02—Traffic management, e.g. flow control or congestion control
  • H04W28/10—Flow control between communication endpoints
  • H04W28/14—Flow control between communication endpoints using intermediate storage
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/06—Synchronising arrangements
  • H04J3/0635—Clock or time synchronisation in a network
  • H04J3/0682—Clock or time synchronisation in a network by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/06—Synchronising arrangements
  • H04J3/0635—Clock or time synchronisation in a network
  • H04J3/0685—Clock or time synchronisation in a node; Intranode synchronisation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/54—Store-and-forward switching systems 
  • H04L12/56—Packet switching systems
  • H04L12/5601—Transfer mode dependent, e.g. ATM
  • H04L2012/5614—User Network Interface
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  • H04L12/56—Packet switching systems
  • H04L12/5601—Transfer mode dependent, e.g. ATM
  • H04L2012/5614—User Network Interface
  • H04L2012/5616—Terminal equipment, e.g. codecs, synch.
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  • H04L12/5601—Transfer mode dependent, e.g. ATM
  • H04L2012/5625—Operations, administration and maintenance [OAM]
  • H04L2012/5627—Fault tolerance and recovery
• • H—ELECTRICITY
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  • H04L2012/5628—Testing
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  • H04L2012/5629—Admission control
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  • H04L2012/5629—Admission control
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  • H04L2012/5635—Backpressure, e.g. for ABR
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  • H04L2012/564—Connection-oriented
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  • H04L2012/564—Connection-oriented
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  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
  • H04L7/04—Speed or phase control by synchronisation signals
  • H04L7/041—Speed or phase control by synchronisation signals using special codes as synchronising signal
  • H04L7/046—Speed or phase control by synchronisation signals using special codes as synchronising signal using a dotting sequence

Definitions

• This invention relates generally to telecommunications and more specifically to a method and apparatus for discarding frames in a communications device.
• ATM communications networks are often interfaced to existing communications networks.
• Examples of communications networks include the telephone network, ISDN networks, frame relay networks, ethernet networks, and/or token ring networks.
• Some existing communication networks that are interfaced to ATM communication networks use frames of information to communicate. When frames are transported through an ATM communications network, the frames are typically broken up into a series of ATM cells wherein the end of a frame is indicated by information in the header of the ATM cell.
• the invention comprises a method and apparatus for discarding frames in a communications network using a series of cells for communication.
• the invention allows frames to be assigned different priorities such that frames having different priorities may be discarded at different levels of congestion.
• One aspect of the invention is a method for discarding frames in a communications device.
• a plurality of cells are received representing a plurality of frames wherein each cell comprises a data portion and a header portion including a cell loss priority indicator. At least some of the cells are stored in a buffer. When a first cell including an end of frame marker is received, it is determined if the number of cells in the buffer exceeds a first threshold.
• the second cell comprises a cell including an end of frame marker.
• the invention has several important technical advantages.
• the invention allows more efficient use of bandwidth in an ATM communications network as an entire frame comprising a series of cells is discarded when congestion occurs, rather than only discarding a portion of the frame.
• the cells in that frame will remain undiscarded unless an overrun condition is detected or the buffer pool limit is exceeded.
• the invention allows cells of a frame to be marked with multiple priority levels using header information of the ATM cells. This feature of the invention allows frames to be discarded at varying levels of congestion depending upon their priority. A lower priority frame will be discarded at a lower level of congestion. The invention may therefore increase the throughput of high priority frames.
• prioritized frame discard frames may be marked as high priority when they use bandwidth below the committed information rate of the frame based communications network and as low priority when they use bandwidth above the committed information rate of the frame based communications network.
• An ATM communications network employing the present invention may then first discard frames that were sent above the committed information rate, providing a fairer distribution of bandwidth among users of the frame based communications network.
• prioritized frame discarding may be used as an input filter in a communications network where the end stations are not flow controlled.
• FIGURE 1 illustrates a block diagram of a communications device constructed in accordance with the teachings of the invention.
• FIGURE 2 illustrates a flow chart describing the steps of discarding frames in accordance with the invention.
• FIGURES 1 through 2 of the drawings like numerals being used for like and corresponding parts of the various drawings.
• FIGURE 1 illustrates a communications device 10 constructed in accordance with the teachings of the invention.
• communications device 10 comprises a switching node in an ATM communications network.
• Communications device 10 could be any type of communications device in a communications network employing a series of cells to pass frames of information through the communications network.
• Communications device 10 comprises a series of input processors 12 coupled to a switch fabric 14. Each input processor 12 is connected to one or more sources of input data. Input processor 12 processes the input data, discards cells as necessary, and passes non-discarded cells to switch fabric 14. Input processor 12 may also convert varying types of data into a series of ATM cells.
• Input processor 12 further comprises processor 16, queue pointers 18, and buffer memory 20.
• Input processor 12 comprises an application specific integrated circuit (ASIC) but could also be any type of electronic circuitry operable to perform the functions described below.
• ASIC application specific integrated circuit
• Processor 16 controls the discarding of cells in communications device 10.
• Cells received by input processor 12 that are not discarded by processor 16 are stored in queues in buffer memory 20.
• each virtual connection is associated with its own queue in buffer memory 20.
• Pointers stored in queue pointer memory 18 are used to keep track of the front and back of each queue in buffer memory 20.
• Each queue associated with a virtual connection may also be referred to as a buffer.
• Input processor 16 determines a maximum size for a queue associated with a specific virtual connection and stored in buffer memory 20.
• processor 16 may assign a buffer associated with a virtual connection to a pool of buffers associated with other virtual connections.
• processor 16 may also place a limit on the maximum number of cells that may be contained in a buffer pool besides limiting the number of cells that may be contained in an individual buffer.
• Processor 16 also maintains counters reflecting the number of cells in a particular buffer associated with a virtual connection. If multiple buffers are associated with a virtual connection, then processor 16 may maintain a counter for each of the multiple buffers. Processor 16 uses the buffer counters to monitor congestion and discard frames if congestion exceeds certain thresholds.
• processor 16 maintains two levels of priority for frames and two congestion thresholds corresponding to those levels of priority.
• Processor 16 could maintain a greater or a lesser number of priority levels without departing from the scope of the invention.
• lower priority frames are discarded after a lower threshold of congestion is encountered while higher priority frames are discarded after a higher level of congestion is encountered.
• This embodiment uses the cell loss priority bit in the header of ATM cells making up a frame to determine the priority of a frame. When the cell loss priority bit has a value of zero, then the frame is considered to be a high priority frame. When the cell loss priority bit is set to one, then the frame is considered to be a low priority frame.
• This embodiment uses the cell loss priority bit of the first cell of the frame to make a determination of whether a frame should be discarded. Ordinarily, the cell loss priority bit of each cell in a frame will have the same value. Other header information could be used to indicate priority without departing from the scope of the invention.
• processor 16 checks for congestion at frame boundaries. If a cell has an end of frame indicator, then processor 16 checks to determine whether either the low congestion threshold or high congestion threshold has been exceeded. If the low congestion threshold has been exceeded, then a state variable is set to indicate that any subsequent frames having low priority (cell loss priority bit equals one) are to be discarded. If the high congestion threshold has been exceeded, then a state variable is set to indicate that any subsequent frame should be discarded. In either case, the end of frame cell is not discarded. If neither congestion threshold was exceeded at a frame boundary, then the state variables are set to a non-discard state so that the subsequent frame will not be discarded.
• Processor 16 determines whether or not a cell contains user data or other data using the payload type indicator for the cell. The payload type indicator appears in the header of the ATM cell. If the check at the end of a frame reveals that the high congestion threshold has been exceeded, then all of the cells in the subsequent frame are discarded, with the exception of the end of frame cell, and processor 16 again determines the state of congestion at the end of the discarded frame.
• processor 16 will again check the level of congestion at the end of the discarded frame.
• Processor 16 may also discard portions of frames when congestion has become so critical that either a buffer overrun has occurred or the number of cells in a buffer pool has reached the pool limit associated with that buffer pool.
• Processor 16 causes cells in discarded frames to be discarded before they are placed in buffer memory 20. This aspect of the invention allows easier manipulation of the queue pointers stored in queue pointer memory 18 as rearranging of the queues is unnecessary.
• FIGURE 2 illustrates a flow chart describing the method by which input processor 12 of FIGURE 1 discards frames.
• the method illustrated in FIGURE 2 employs two state variables to determine whether or not to discard frames.
• the first state variable, discard frame state is set when the level of congestion has reached a point at which all frames should be discarded and cleared otherwise.
• the second state variable, discard CLP1 frame state is set when the level of congestion is high enough to discard frames having a cell loss priority equal to one (low priority) . This variable is cleared otherwise.
• step 22 The method begins in step 22 with initialization. Initially, the state variables are cleared in step 22.
• step 24 a cell is received.
• step 26 it is determined if the cell is user data or an end of frame cell, if the cell loss priority is equal to one, and if the discard CLP1 frame state is set.
• a cell is considered to be user data when its payload type indicator equals 0 or 2.
• a cell is considered to be an end of frame cell when its payload type indicator is equal to 1 or 3.
• the payload type indicator appears in the header of the ATM cell. If all of the conditions are met in step 26, then the current frame is to be discarded as it has a cell loss priority equal to 1, the level of congestion is sufficiently high to discard frames of that type, and the frame contains user data.
• step 28 the discard frame state variable is set in step 28. Following step 28 or if all the conditions were not met in step 26, the procedure continues in step 30. Note that step 26 depends upon the state of the discard CLP1 frame state variable which is only altered when processing an end of frame cell at the frame boundary.
• step 30 it is determined whether the cell has an end of frame marker. If not, then the process continues in step 44. If so, then a frame boundary has been reached and the congestion in the network should be examined. Accordingly, the process continues in step 32 where it is determined whether the buffer has reached the high congestion threshold. If so, then the discard frame state variable is set in step 42 and the procedure continues in step 44. If not, then the discard frame state variable is cleared in step 34 in case the variable was set for the previous frame. Then, in step 36, it is determined whether the buffer has reached the low congestion threshold. If not, then the discard CLPl frame state variable is cleared in step 38 in case it had been set for the previous frame. If the low congestion threshold has been reached, then the discard CLPl frame state variable is set in step 40.
• step 44 it is determined whether the pool limit has been exceeded or a buffer overrun condition has occurred.
• several virtual connections may share a buffer pool. If the limit of this buffer pool is exceeded, then the current cell should be discarded immediately in step 46 as there is no place to put the cell. Similarly, if a buffer overrun has occurred, the cell should also be discarded in step 46 even though such a discard may occur in the middle of a frame.
• step 48 it is determined if the cell is user data or an end of frame cell. If not, then the procedure returns to step 24 to receive the next cell. If so, then the discard frame state is set in step 50.
• step 50 Setting the discard frame state in step 50 will cause the rest of the frame from which the cell was discarded in step 46 to also be discarded. Because one cell of the frame was already discarded, the rest should also be discarded to avoid wasting bandwidth. As above, the end of frame cell will still be sent if the buffer overrun condition or pool limit overrun condition is no longer present when the end of frame cell is received.
• step 52 it is determined whether the discard frame state variable is set and whether the current cell contains user data. If not, then the procedure returns to step 24 to process the next cell. If so, then the current cell is discarded in step 54 and the procedure then loops back to step 24.
• the process in FIGURE 2 thus checks for congestion at frame boundaries as each end of frame cell is received. If the level of congestion exceeds the predetermined threshold appropriate for the following frame, then the cells of the following frame with the exception of the end of frame cell are discarded. This process thus utilizes network bandwidth more efficiently and allows prioritized discarding of frames.

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• 1996
  • 1996-07-18 AU AU65032/96A patent/AU6503296A/en not_active Abandoned
  • 1996-07-18 JP JP9506892A patent/JPH11510014A/ja active Pending
  • 1996-07-18 EP EP96924631A patent/EP0872086A4/fr not_active Withdrawn
  • 1996-07-18 WO PCT/US1996/011960 patent/WO1997004567A1/fr not_active Ceased

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