JPH11510009A - Assignable and dynamic switch flow control - Google Patents

Abstract

SUMMARY A method and apparatus for eliminating cell loss in a network switch through the use of both allocated and dynamic bandwidth flow control is disclosed. When the output buffer (28) in the switch is filled to a predetermined threshold level, a feedback message (30) is provided to the input buffer (26) to prevent transmission of cells from the input buffer to the output buffer. To provide connection-type and traffic-type isolation, buffers are grouped into queues and flow control can be performed on a per queue basis. The feedback message is a digital signal including an ACCEPT / REJECT message and a NO-ON / XOFF message. The XOFF message may be received during transmission over allocated or dynamic bandwidth.

Description

DETAILED DESCRIPTION OF THE INVENTION                     Assignable and dynamic switch flow control                              TECHNICAL FIELD OF THE INVENTION   The present invention relates generally to communication networks, and more particularly to the reduction of cell loss in a network switch. I do.                               Related patent application   This application is related to US Provisional Patent Application No. 60/001, filed July 19, 1995. No. 498.                                Background of the Invention   Networks such as Asynchronous Transfer Mode ("ATM") networks provide audio, video and other data Used to transfer. ATM networks are data units such as ATM cells Data by routing data from source to destination through the switch I do. The switch uses input / output (I / O) through which ATM cells are received and transmitted. "I / O") ports. The appropriate output port for cell transmission is the cell header Is determined based on   One problem associated with ATM networks is cell loss. Cell routing Are buffered in the respective exchange before it and transmitted from the switch. Further Specifically, switches are typically used to temporarily store cells before transmission. Have a buffer at either the input or the output. As network traffic increases Insufficient buffer space increases the possibility of data loss. Buffer size If not, cells will be lost. Cell loss refers to audio and video data Causing undesired interruptions in transmission, more than other types of data transmission Can cause significant damage. Therefore It is desirable to avoid cell loss.                                Summary of the Invention   Method and apparatus for eliminating cell loss in a network switch by using flow control Is disclosed. The switch has at least one input port and at least one output port. Input port and input and output buffers associated with the input and output ports, respectively. . Cells enter the switch through input ports and are buffered in input buffers. It is. The cells are then transmitted from the input buffer to the output buffer and then to the output port Transmitted. When the output buffer is filled to a predetermined threshold level, the input buffer Feedback to the input buffer to prevent cell transmission from the A message is given. Therefore, the cell loss between the input and output buffers Is prevented by flow control.   Buffers are keyed to provide both connection-type and traffic-type isolation. Queues, and flow control is performed for each queue. Each queue is Each switch contains a number of input queues and a number of output queues. No. When entering the switch, each cell is used for final transmission to a specific output queue. Loaded to a specific input queue. Next, when shared resources are used, traffic Each queue is a traffic-type group to provide traffic-type flow control. Assigned to the group. In another implementation, each queue has a variable bit rate ("VB R ") service class and effective bit rate (" ABR ") service class Specific traffic types (sometimes called service classes) Can be Flow control can be implemented for each traffic type. Furthermore, the flow Control is based on the traffic subtype in which each queue can be assigned to a particular connection. On the traffic subtype. Sometimes per connection Provides flow control. Table 1 below shows possible flow control configurations.   Each connection is banded based on the traffic type associated with the connection. Bandwidth type is assigned. Within the exchange, allocatable and dynamic bandwidth Two types of bandwidth are allowed. Allocated bandwidth is the amount of bandwidth allocated The bandwidth "remaining" to be used by the connection. Generally, allocation Connections with a type bandwidth are all of the bandwidth allocated to the connection. Access to the quantity of is guaranteed. Thus, the deterministic delay Allocated bandwidth is assigned to traffic types that require control. Dynamic belt Bandwidth is the bandwidth "shared" by various competing connections. Dynamic bandwidth Since bandwidth is a shared resource, generally certain connections have access to a certain amount of bandwidth. Is not guaranteed. For this reason, dynamic bandwidth typically has a larger delay range. Assigned to a connection that has an enclosure. Other connections have a dynamic bandwidth And a combination of allocatable bandwidths.   To facilitate flow control, a digital filter having first and second bits is provided. Feedback message is given. Feedback messages are sent to the output queue From the input queue. More specific Use the first bit of the feedback message and the first bit = 0 The cell Indicates the ACCEPT of the input queue request to be transferred to the output queue. Requested input queue When the ACCEPT is received by the host, the cell is transferred to the output queue.   The feedback message may also include a REJECT message. Request When the REJECT is received by the input queue, the cell is not transferred. Only Meanwhile, requests for further transfer can be sent by the input queue.   The feedback message may also include a NO-OP / XOFF message . XOFF messages are received during transmission over allocatable or dynamic bandwidth. Can be trusted. In particular, XOFF (assignment) messages are received for assigned bandwidth. Yes, XOFF (dynamic) messages may be received for dynamic bandwidth. Additional tagging techniques to distinguish between dynamic and allocated bandwidth requirements Surgery may be used. XOFF (dynamic) messages indicate that the transmission of a request Temporarily stop transmissions through. XOFF from specific output queue (dynamic ), Each input queue receives dynamic bandwidth until the specified event occurs. Temporarily stop making requests to send to that particular output queue. Designation The specified event has passed the specified time or a request for further transfer has been sent. XON signal is received. Input queues are also regular, ie when each XO regardless of whether a particular input queue has been placed in the XOFF (dynamic) state. It can be enabled by the N signal. Such a regular criterion is, for example, 100 Every second. When the second bit of the 2-bit message is 0, this is NO- Indicates an OP (inactive) signal. Each input queue that receives a NO-OP signal cannot be used. Not enabled.   XOFF (allocated) feedback messages are transmitted over allocated bandwidth Temporarily stop transmitting the request. XOFF from a specific output queue Each input queue that receives the type is specified Until the specified event occurs, it is sent to that particular output queue through the allocated bandwidth. Temporarily stop making requests to trust. The specified event is typically updated Reception of an XON signal that allows the transmission request to be transmitted. Input key The queue is also regularly, ie, when each particular input queue is in the XOFF (allocated) state. It can be enabled by the XON signal regardless of whether it has been placed. like that A regular criterion is, for example, every 100 milliseconds. The second of the two-bit message When the bit is 0, this indicates a NO-OP signal. NO-OP (non-operation) signal The respective input queue to receive the data has not been disabled.   In the preferred embodiment, the XON signal is an input key placed in any of the XOFF states. Used to enable Each input that receives XON from a specific output queue The power queue is enabled to issue requests to transmit to its output queue. More special Specifically, XON resets both XOFF (dynamic) and XOFF (assigned) states. Cut. The XON signal reduces unnecessary switch traffic and reduces error traffic. Used together with regularly enabled, both to prevent row blocking Can be done.   Requesting input queues receive various combinations of responses to transmission requests It is clear that this can be done. NO-OP and ACCEPT or REJECT Reception operates as described above. XOFF (dynamic) and ACCEPT or XOFF (Allocated) and ACCEPT reception is diverted through the specified bandwidth. Stop the transfer of one cell followed by further requests to send. XOFF (dynamic) and RE The reception of either JECT or XOFF (assignment type) and REJECT is specified. Further requests to transfer over the allocated bandwidth stop immediately and no cells are transmitted. No. Thus, while the XOFF command affects future requirements, REJ The ECT command provides for rejection of the current request.   NO-OP / XOFF (dynamic) messages are unnecessary feeds in the switch. Used to reduce back signaling. The switch bandwidth is If it cannot be transmitted through the switch and the REJECT appears repeatedly, Used inefficiently. Therefore, XOFF (dynamic) means that Switch ("FSPP") queue to reduce the number of requests for the entire queue Used to change the port processor ("TSPP").   Flow control using the feedback messages described above is a reliable Point-to-multipoint transmission, i.e. multiple outputs from a single input queue. Provides transmission to the force queue. In point-to-multipoint operation, multiple outputs Feedback messages from a power queue to a single input queue can be A single XOFF (dynamic) or REJECT message from any one of the The logical OR is set so that the message prevents transmission. Therefore, point-to-multi Point cells are transmitted at the rate of the slowest destination queue.   The flow control by the 2-bit feedback message described above also Medium reliable multipoint-to-point transmission, i.e. from multiple input queues Provides transmission to a single output queue. Each output queue has a threshold and the output queue Sends an XON message when it has exhausted its threshold. Multipoints In point operation, the XON threshold of the output queue is determined by the Set dynamically to leave enough space for transmission. For example, 8 inputs If there is a queue, the output queue is filled to receive all cells sequentially during the same period. The threshold is set to 8 to free up space.                             BRIEF DESCRIPTION OF THE FIGURES   The above and other features of the present invention will be described in detail with reference to the accompanying drawings. Will be obvious. In the figure,   FIG. 1 shows a switch interconnect block diagram;   Figure 2 illustrates point-to-point operation, switch flow control and link flow control. FIG.   FIG. 3 is a block diagram showing a point-to-multipoint operation.   FIG. 4 is a block diagram showing a multipoint-to-point operation.                             Detailed description of the invention   Referring now to FIG. 1, the switch comprises an NxN switch body 10 and a bandwidth arbiter. And a plurality of switch terminating port processor subsystems ("TSPP"). 14, a plurality of exchange receiving port processor ASICs 15, and a plurality of exchanges Incoming port processor subsystem ("FSPP") 16 and multiple switch originating Side port processor ASIC 17 and multiple multipoint topology controllers And 18. NxN switch body such as ECL cross point switch body , Used for cell data transport, with N times the throughput of 670 Mbps Produces a put. The bandwidth arbiter controls the switch Dynamic scheduling of unallocated bandwidth for multipoint-to-point Resolve regional competition. Each TSPP sends information from a number of connections to the switch itself. Schedule transmission of files. Between the input link and the TSPP subsystem The physical line interface is not shown. The FSPP is sent from the switch body. And organize these cells on the outgoing link. Output link and FSP The physical line interface to the P subsystem is not shown.   Referring now to FIG. 2, the switch includes a plurality of input ports 20 and a plurality of output ports. Ports 22 and their respective input and output ports And an input buffer 26 and an output buffer 28 attached thereto. To go through the exchange At the same time, the cell 24 enters the switch through the input port and is buffered in the input buffer. Ringed. The cells are then buffered from the input buffer to the output buffer in the output port. Falling. From the output port, the cell is connected to the outside of the switch, for example another switch 29. Transmitted to In response to a transfer request, the output buffer fills up to a predetermined threshold level. Input port to prevent transmission of cells from the input port to the output buffer. A feedback message 30 is provided.   Feedback message 30 prevents cell loss in the switch. To output buffer If the number of transmitted cells 24 is greater than the number of available output buffers 28 , Cells are lost. However, in response to the transfer request, the output buffer If the threshold level is met, the input buffer will prevent transmission of cells from the input buffer. The feedback message 30 is transmitted to the port 20. Threshold level used Set a value that prevents transmission of more cells than can be handled by the possible output buffers. Is set. Therefore, cell loss between the input and output buffers is Prevented by feedback messages.   To provide both connection-type and traffic-type isolation,   Buffers 26 and 28 are organized into queues 32 and 34, respectively, with one flow control Is performed for each queue. Each queue contains a number of buffers, each input port and The output port includes a number of input queues 32 and a number of output queues 34. To exchange Upon entry, each cell 24 is designated for final transmission to a particular output queue 34. It is loaded into the input queue 32. Traffic resources when shared resources are used Queues are assigned to traffic-type groups to provide Hit. By assigning only one queue to a connection, -Control can be performed for each connection. In addition, one traffic type One for each A nested queue of queues is used to provide per-connection flow control. Can be.   For multipoint topologies, many queues per connection Required and circuitous to implement per-connection flow control. In the TSPP, if there are multiple sources for a multipoint connection, Multiple queues are nested in the scheduling list 48. In TSPP If there is a single source, the scheduling list is still used, but It has one queue. The scheduling list actually indicates that the queue is Queue that has cells to be transmitted for There is a scheduling list for each connection, and the TSPP Support Nection. Therefore, the scheduling list is used as an input queue. The terms are used interchangeably below.   Each connection is based on the traffic type associated with the connection. Is assigned a bandwidth type. Within the switch, allocated and dynamic bandwidth Two types of bandwidth are allowed. Allocated bandwidth is the cost to which the bandwidth is allocated. The bandwidth "remaining" to be used by the connection. Generally, allocation A connection with a typed bandwidth will have all the amount of the typed bandwidth allocated to that connection. Access is guaranteed. Thus, deterministic control over delay Allocated bandwidth is allocated to the required traffic types. Dynamic bandwidth is , Bandwidth that is “shared” by various competing connections. Dynamic bandwidth is shared As a resource, a particular connection generally has access to a certain amount of bandwidth Is not guaranteed. Because of this, dynamic bandwidth typically has a larger delay range Assigned to the connection. Dynamic and allocated bandwidth for other connections May be assigned.   Connections that use dynamic bandwidth, allocated bandwidth, or both Each transfer request is tagged to distinguish cells associated with the service. Change More specifically, a transfer request for a connection using dynamic bandwidth is in a first state. Requests to transfer connections that are tagged with bits and use allocatable bandwidth The second state bit is tagged. Cell rate to which the connection was allocated Works at or below, the transfer request is tagged as assigned .   Referring now to FIGS. 1, 2 and Table 2, the feedback message 30 is required. Provided in response to the request message 36. From input port 20 to output port 22 Before transmitting the cells, is there sufficient buffer 28 available in the output port? To determine whether to include an allocatable / dynamic tag from the input port to the output port 22 Request message is sent. Feedback message 30 goes to output port Provide an indication of the buffer status at which point the transmission proceeds. The cell is the selected item The request message 36 always precedes the cell transfer so that .   Feed from output port to input port to provide effective flow control Back message 30 includes several subtype messages. For example, fee The debug message is an ACCEPT message that can be sent in response to the request message. Including messages. A 1-bit digital signal is used, and the first bit = 0 is Output Indicates the ACCEPT of the input queue request to be transferred to the queue. To the requested input queue Thus, when the ACCEPT is received, the cell is transferred to the output queue.   Feedback message 30 may also include a REJECT message. Change Specifically, the response to the request message is an ACCEPT or REJECT message. Page. Using a 1-bit digital signal, the first bit = 1 Indicates REJECT of a request to transfer a cell to an output queue. Requested input queue When the REJECT is received by the client, the cell is not transferred to the output queue. I However, a further request message 36 is sent from the input queue to the output queue. sell.   Feedback message 3 to reduce unnecessary message traffic 0 also temporarily stops transmission of request message 36 over dynamic bandwidth XOFF (dynamic) message. 2-bit digital feedback The second bit = 1 indicates XOFF (dynamic). Specific output queue Each input queue 32 receiving XOFF (dynamic) from the designated Request for dynamic bandwidth for that particular output queue until Temporarily stop the transmission of the message. The specified event has passed the specified time, or Is received. The second bit = 0 is NO-OP, that is, XOFF (dynamic) Indicates an inactive message which means not asserted.   The feedback message is also an XOFF (assignment type) feedback message. May be included. Each input queue that receives XOFF (assignment type) from a specific output queue Is assigned to that particular output key through the allotted bandwidth until the specified event occurs. Temporarily stop making requests to send to the queue. The specified event is typical Is the reception of an XON signal which allows a request for further transfer to be sent . The input queues are also regular, i.e., when each particular input queue is XOF Enabled by the XON signal, regardless of whether it has been placed in the F (assigned) state. Can be Such a regular criterion is, for example, every 100 milliseconds.   Actually, the request tagging technology indicates XOFF (dynamic) or XOFF (assignment type). Allows the use of a single XOFF message for Request tagging technology Tag bits based on whether the request is for dynamic bandwidth or allocated bandwidth Tags bandwidth requests by bandwidth. Thus, the tag bits are assigned Request and dynamic request and feedback, i.e. dynamic bandwidth The XOFF transmitted in response to the request is XOFF (dynamic).   Using a 2-bit feedback message, depending on the input queue requested Various responses to each request message may be received. Such a response is Is interpreted as follows. NO-OP and reception of ACCEPT or REJECT are as follows It works like The reception of XOFF (dynamic) and ACCEPT Indicates that a further request will stop the subsequent transfer of one cell. XOFF (dynamic) and Receipt of a REJECT will immediately stop further requests for transfer and the cell will not be transmitted at all. Indicates that it will not be sent. In this way, the XOFF (dynamic) command is While influencing, the REJECT command provides for rejection of the current request.   The feedback message 30 enables further transmission of the request message XON messages. An XON message is a It occurs synchronously and is not given in response. XON messages are both This is effective for removing the XOFF condition. Receive XON from specific output queue Each incoming queue can make a request to forward to its output queue Has been.   To reduce the likelihood of lockups occurring in switch flow control, Irrespective of removal or failure of internal elements such as ports It is desirable to use a timeout type function that allows continued operation. An example For example, after receiving the XOFF (dynamic or allocation type) message, the specific output queue 3 Input queue 32, which has stopped transmitting request messages to If no XON message is received from the output queue, the Further request messages may be transmitted. Alternatively, the input queue is set to XOFF (dynamic Request message may be transmitted periodically regardless of the status (target or allocation type).   Referring again to FIG. 1, the present invention will be described in more detail. Desired architecture In each channel, each input port includes TSPP14 and each output port includes FSPP16. Including. TSPP and FSPP are organized into queues 32 and 34, respectively. And RAM. All cells in connection 40 have a lifetime of the connection. For each port, one is in the TSPP and the other is a single in the FSPP. Go through the queue. Thus, the queue maintains cell order. This method also has one Quality of service ("QoS") for each connection.   The request message 36 indicates that sufficient buffer 34 is available for cell transmission. The protocol sent from TSPP14 to FSPP16 to determine if It is. To ensure that no cells are lost in the switch, the TSPP Sends cell to FSPP unless there is available buffer space for that cell Can not do it. To determine buffer status, the probe sends a cell Communicate the destination multi-queue number indicating the FSPP queue to be sent. For example, The destination multi-queue number may identify output queue 34a as the destination queue. That If no buffer space is available in the queue, as described below, The SPP is either “REJECT” or “XOFF (dynamic or allocation type)” or Responds to the probe by both.   To implement switch flow control probes and feedback messages , Three communication paths: a probe crossbar 42 and an XOFF crossbar 44 And the XON crossbar 46 are used. Probe crossbar 42 is FSPP NxN crosspoint used to transmit multi-queue numbers to each FSPP It is the exchange body. Multi-queue numbers use point-to-multipoint Identify multiple destination queues for a cell for The FSPP uses the probe 36 To the appropriate output queue 34 so that the That there are enough output buffers available in the destination queue for receiving messages To determine. For point-to-multipoint, there are many multi-queue numbers. There is only one multi-queue number per connection per FSPP.   The XOFF crossbar 44 is a “transmission disabled” type from FSPP16 to TSPP14 NxN serial crosspoint switch used to communicate multiple messages The main body. Each TSPP has a queue of cells to be transmitted for each connection. A number of scheduling lists 48 with Feedback message The first bit of the page 30, ie, WOFF, is the scheduling list of the specific TSPP. Asserted to stop transmitting the request message probe 36, A state control bit for setting the scheduling list of the received TSPP to the XOFF state. The scheduling list 48 of the TSPP does not use dynamic bandwidth. Means that The scheduling list of this TSPP is XOFF state until a message is received. The second bit, REJEC T indicates that insufficient buffer space is available to receive cells without FSPP Asserted in some cases. This state indicates that the FSPP destination queue is full Or the entire output buffer pool is depleted. TSPP Does not dequeue cell 24 through data crossbar 47, To Respond to the REJECT feedback message. Instead, it is supplemented The idle cell indicated by the CRC is transmitted. TSPP is Assert by changing the XOFF status bit in the scheduling list Responsive to the received XOFF (dynamic) feedback message. XOFF state Until the cell buffer is available by the FSPP. SPP sends request message from its queue on its scheduling list Prevent trying.   XON crossbar 46 is used to communicate "sendable" type messages NxN serial contention based switchboard. More specifically Indicates that the XON crossbar 46 communicates XON messages from the FSPP to the TSPP. Used to If the number of buffered cells in the FSPP queue is X XON message is sent from FSPP to TSPP when it falls below ON threshold Is done. XON message is TSPP scheduling list request message To resume transmission of   FIG. 3 illustrates a point-to-multipoint switch flow control, ie, a single input queue. -32 to a number of output queues 34. Point-to-multipoint In operation, the XOFF crossbar performs a logical OR function. More specifically, X The OFF crossbar will be sent by the FSPP to provide a single feedback message. The logical OR of the feedback message 30 asserted is executed. result REJECT or XOFF from any FSPP is received by RE A single result flag that is interpreted as asserting JECT and / or XOFF. Causes a feedback message. This technology allows TSPP to be the slowest destination key. Limit transmission at the queue rate. However, this technology also Provides continuous transmission for the desired synchronization.   In the case of point-to-multipoint transmission, the TSPP uses multiple XOs. It can be seen that N messages can be received. This means that many XOFF Therefore, one or more FSPPs may set XOFF for a transfer request. This is because it can be asserted. In such a case, the TSPP scheduling list XON messages received when the XOFF status of the It is. For example, when a large number of XON messages are sent, the TSPP first receives Ignore the XON received after the received XON message. Multi point In case of two-point transmission, the scheduling list is transferred to the FSPP queue. , XON messages are sent to all TSPPs simultaneously.   FIG. 4 shows a multipoint-to-point switch flow control, ie, multiple input queues. FIG. 3 illustrates transmission from 32 to a single output queue 34. Each output queue has a threshold XON message is sent when the output queue drops below that threshold You. In multipoint-to-point operation, the XON threshold of the output queue is Dynamically set so that the queue leaves enough buffer to transmit to the output queue Is done. For example, if eight queues are transmitting, the output queue will be all eight cells The threshold is set to 8 to free enough buffers to receive Set, thus ensuring that each queue has a chance to transmit.   Referring now to FIGS. 1 and 4, a multipoint-to-point connection , Regardless of whether the TSPP is transmitted to the asserting FSPP queue. XON clock to broadcast to all TSPPs in the exchange. A subbar 46 is used. Multipoint topology for broadcast Controller 18 transmits reverse broadcast channel number instead of FSPP I do. The next receiving multipoint topology controller determines which schedule Reverse broadcast channel to determine whether to enable Vs scheduling list number look Run up. T for which there is no queue to transmit for that particular FSPP queue SPP states that reverse broadcast channel number lookup entry is invalid Is not affected by the broadcast XON message. No.   Referring again to FIG. 2, with additional flow control enhancements, the queue is The output queue is organized according to a hierarchy having a number of individual flows 52 in the bell. Feedback messages 30 from the queue to the input queue are combined at each hierarchical level It is formed based on the performed flow. Another emphasis is that queues are at each hierarchical level Is organized based on a hierarchy with a large number of individual flows and inputs from output queues Feedback messages to the queue are formed based on each individual flow .   The probe & XOFF communication path operates in a pipeline format. First, TSPP 14 selects an input queue 34 and information associated with that queue is output to an output port for transmission. Used to determine the destination or destination output queue. Bandwidth arbitrator Uses this information to control successive probes, TSPPs and crosspoints. Down to the TSPP to FSPP connectivity map used for More specifically, FSPP multi-queue number transmitted to FSPP using probe crossbar 42 Is done. Next, the FSPP tests the availability of the buffer, If the key is not available, REJECT and / or XO on the XOFF crossbar Assert FF. Next, the TSPP asserts if REJECT is asserted. Transmit the idle cell. If XOFF is asserted, the TSPP will be scheduled The list to the XOFF state. TSP if enough buffers are available P uses the data crossbar 47 to transfer the cell to the FSPP output queue.   Table 3 shows that REJEC according to the request tagged as using dynamic bandwidth Summarizes the method used by the FSPP to assert T and XOFF I do. The method has two relationships: traffic type cell counting with respect to cell counting limits. And the dynamic buffer count of the queue with respect to the buffer count limit. Traffic Type cell count is applied to connections in traffic type, eg "VBR" Thus, it is a count of all cells that are shared. REJE if limit is not exceeded Neither CT nor XOFF is asserted. More specifically, the traffic If the ipcell count is below the limit and the queue dynamic buffer count is below the limit, In this case, neither REJECT nor XOFF is asserted. Traffic type If the cell count is less than the limit but the queue dynamic buffer count is In this case, both REJECT and XOFF are asserted. Traffic type cell If the count is above the limit and the dynamic buffer count of the queue is below the limit, X OFF is not asserted, but REJECT is asserted. Traffic ties If the Pussel count is over the limit and the queue dynamic buffer count is over the limit , REJECT and XOFF are asserted.   Table 4 shows REJECT and REJECT on request tagged using allocated bandwidth. Summarizes the method used by the FSPP to assert XOFF and XOFF . The method has three relationships: buffer status counting with respect to the buffer status counting limit; Traffic type cell count for cell count limit and buffer count limit for cell count limit Based on the queue's allocated buffer count. Link flow control is Use the buffer status counter to indicate The allocated buffer status Counters for the assigned components of the connection using link flow control. Used to record the cell being transmitted. Queue allocated buffer State count is greater than the count limit and traffic type cell count is greater than the cell count limit. Yes, when the queued buffer count is greater than or equal to the count limit, REJE Neither CT nor XOFF is asserted. The allocated buffer of the queue When the count is above the buffer count limit, both REJECT and XOFF Will be asserted. Queue assignments Buffer count is less than the count limit, but the queue's allocated buffer status Either the count is above the count limit or the traffic type cell count is above the cell count limit. At one time, REJECT is asserted, but XOFF is not. all In all cases, if the FSPP queue has already sent XOFF, Assert XOFF again with the probe.   Various changes and modifications to the methods and apparatus described above may occur in connection with the new features disclosed herein. It will be appreciated that this can be done without departing from the concept. Therefore, the present invention It is considered that the present invention is not limited to the embodiments.

[Procedure of Amendment] Article 184-8, Paragraph 1 of the Patent Act [Submission date] February 27, 1997 [Correction contents]                                The scope of the claims 1. A plurality associated with a plurality of input ports forming at least one input queue Forms at least one output queue with the input buffer of At least one input switch in a network switch having an associated output buffer. A method for controlling the flow of a data unit, comprising:   At least one input data received at at least one input port Receiving the unit into the exchange;   At least one input data unit to at least one output port Forwarding the request for transmission;   At least one for receiving at least one input data unit Authorize the transmission request if sufficient output buffers associated with the output port are available To do,   At least one for receiving at least one input data unit If there are not enough output buffers available for the output port, the transmission request is rejected. Rejecting,   At least one input data unit is reduced if the request issued is granted. Transmitting from at least one input port to at least one output port;   At least one input data unit if the transmission request is rejected Delaying transmission from at least one input port to at least one output port A method consisting of 2. The step of transmitting differs in at least one input data unit A transmission to each of a plurality of output queues associated with the output port. The method of claim 1. 3. At least one input data unit has at least one Receiving at one of the input queues and forwarding the request comprises at least one input queue. At least one of each of the input data units addressed to At least one input data unit in each output queue of the output queues. When a unit is received, the request is transferred from each input queue of at least one input queue. Sending each transmission request to a respective input queue and output for each transmission. The method of claim 1, wherein the method is specific to the queue. 4. At least one connection is established through the switch and the selected Assigning at least one input queue and one output queue to a connection Floors, whereby flow control is performed for each connection. The method of claim 3. 5. Assign each input queue and output queue to the selected service class Each service class is associated with a transmission priority level and Sending requests are allowed and denied based at least in part on the priority level; The method of claim 3. 6. Each input key for the selected connection and the selected service class Queue and output queue, each service class having transmission priority. Level, so that flow control is done on a connection-by-connection basis. And one service class, and the transmission request is at least partially 4. The method of claim 3, wherein permission and denial are based on a preference level. 7. In response to the transmission request, includes a first signal indicating permission or denial of the issued request. Providing at least one input key. At least one input data unit in the queue is At least one if indicated At least one output queue if the message indicates rejection. 4. The method of claim 3, wherein said method is not transmitted to a server. 8. Stop forwarding transmission requests as part of the feedback message Providing a second signal indicating either a command or a non-actuation. Each input receiving an instruction to stop forwarding transmission requests from one output queue The power queue is an output queue given an instruction to stop forwarding the transmission request. The method according to claim 7, wherein the transmission request is stopped. 9. For transmission from a single input queue to multiple output queues, a single input queue At least one output so that transmissions from the For each of the first and second signals of the feedback message from the force queue 9. The method of claim 8, further comprising performing a logical OR operation. 10. For transmission from multiple input queues to a specific output queue, multiple input queues To provide enough buffer for synchronous reception of data units from the queue. Command to stop forwarding the transmission request by a particular output queue. The method of claim 8, further comprising setting a threshold value. 11. Sufficient buffers are available to receive a given number of data units At least one of the at least one input queue has at least one output By re-enabling forwarding of transmission requests to one of the queues Providing a third signal for canceling the command to stop transmitting the transmission request. 9. The method of claim 8, further comprising: 12. Dequeue data units from one of at least one output queue. 12. The method of claim 11, further comprising the step of providing a third signal when performing. 13. When one of the at least one output queue drops below a threshold One of the at least one output queue to provide a given third signal 14. The method of claim 13, further comprising setting a threshold value within. 14． After a predetermined time has elapsed following the transmission of the second signal, at least one Providing a third signal to one of the input queues of Item 12. The method according to Item 11. 15. To one of at least one input queue based on regular time The method according to claim 11, further comprising the step of providing a third signal to the signal. 16. From one of at least one output queue to multiple input queues 12. The method of claim 11, further comprising providing a third signal. 17． Input and output buffers are organized into a number of individual data Further comprising the step of organizing into a hierarchy of levels having a unit flow, each level Feedback messages for each level based on the combined flows in the bell 3. The method of claim 2, wherein a sage is provided. 18. Input and output buffers are organized into a number of individual data Organize into a hierarchy of levels with unit flows Further comprising the step of providing a feedback message for each individual flow. 3. The method of claim 2, wherein 19. Controlling the flow of at least one data unit in a telecommunications network A network switch,   At least one input port for receiving a data unit input to the switch; ,   At least one output port for transmitting data units out of the switch;   Encodes incoming data units received at each input port for transmission. At least one input buffer associated with the at least one input port to queue; Faque and   An input data unit received from the at least one input buffer queue. Associated with the at least one input buffer queue for receiving and temporarily storing At least one output buffer queue,   A specific output buffer from the input buffer queue where the data unit is enqueued First indicating permission authorization to transmit at least one data unit to the queue. Status and input buffer queue from the at least one output buffer queue. Second state indicating a denial of permission to transmit a data unit enqueued to one of the The feedback message having the status At least one feedback message operable to provide to the queue A network switch consisting of a generator. 20. The at least one of the at least one input buffer queue from the at least one At least one data unit to the one of the one output buffer queues At least one transmission operable to generate a signal requesting permission to transmit A request generator; At least one feedback message generator is configured to transmit the at least one transmission message. Providing the feedback message in response to a permission request signal from the request generator; An exchange according to claim 19. 21. 21. The output port of claim 20, wherein each output port includes a feedback message generator. Onboard exchange. 22. Multiple connections are established in the exchange, and each of the above Uses at least one single input queue and at least one single output queue 20. The method according to claim 19, wherein the flow control is performed for each connection. Onboard exchange. 23. At least one input queue and at least one output queue are selected. Assigned to a given service class, whereby flow control is assigned to one service class. 20. The switch of claim 19, wherein the switch is performed for each lath. 24. Multiple connections are established in the switch, each input queue and each output Queues are assigned to selected connections and selected service classes. , Whereby flow control is per service class and one service class 20. The switch of claim 19, which is executed every time. 25. Includes a first signal indicating whether the issued request was granted or rejected. Wherein the feedback message is provided in response to the permission request signal. The exchange described in 0. 26. Enqueued if the first signal indicates that transmission permission has been granted Data is transmitted and the first signal is denied transmission permission Enqueued data is not immediately transmitted if it indicates that Item 30. The exchange according to Item 25. 27. The feedback message sends a permission request signal when each is inactive. And a second signal having first and second states indicating an instruction to stop Each input receiving a second signal in a second state from one of the plurality of output queues. The power queue stops issuing transmission requests to one of the plurality of output queues The exchange of claim 20, wherein 28. For transmission from a single input queue to multiple output queues, a single input queue The transmission from a queue to a plurality of output queues is performed such that the transmission is performed serially and synchronously. For each of the first and second signals of the feedback message from the force queue 28. The switch of claim 27, comprising a logic circuit that performs a logical OR operation. 29. For transmission from multiple input queues to a specific output queue, multiple input queues In order to provide sufficient buffer for synchronous reception of the transmission from the queue, a second Dynamically adjustable when a second signal in a state is provided in relation to a particular output queue 28. The switch of claim 27, wherein the threshold is increased. 30. One of the plurality of input queues becomes one of the plurality of output queues To the second state by re-enabling the The plurality of input queues from one of the plurality of output queues to cancel a second signal. 28. The exchange of claim 27, wherein a third signal is provided to one of the force cues. Machine. 31. The third signal is from one of the plurality of output queues. 31. The switch of claim 30, provided when dequeuing a data unit. 32. Given when one of the output queues drops below a threshold The threshold is set in one of a plurality of output queues to provide the third signal. 31. The switch of claim 30, wherein the switch is installed. 33. After a lapse of a predetermined time following reception of the second signal in the second state Wherein said third signal is provided to one of said plurality of input queues. Item 30. The exchange according to Item 30. 34. The second one for a plurality of the input queues based on a regular time. 31. The switch of claim 30, wherein three signals are provided. 35. The third from one of the plurality of output queues to the plurality of input queues; 31. The switch of claim 30, wherein the switch is provided. 36. The at least one input buffer and the at least one output buffer Each of the levels with a large number of individual data unit flows at each hierarchical level Arranged in a hierarchy, wherein the feedback messages are combined at each level 20. The switch according to claim 19, wherein the switch is provided for each level based on the flow. 37. The at least one input buffer and the at least one output buffer Each of the levels with a large number of individual data unit flows at each hierarchical level Arranged in a hierarchy, and the feedback message is given to each of the individual flows. An exchange according to claim 19, obtained. 38. A plurality of input buffers associated with at least one input queue; Network switch having a plurality of output buffers associated with one output queue Controlling the flow of at least one input cell, comprising:   At least one input cell received in the input queue of the input memory Receiving in the exchange;   Transmitting at least one incoming cell to the at least one output queue Forwarding the request;   Sufficient buffer in the output queue to receive at least one incoming cell Authorizing the transmission request if the key is available;   Sufficient buffer in the output queue to receive at least one incoming cell Rejecting the transmission request if the key is not available;   Allocated requests will be allocated if granted, and fewer requests will be made for dynamically available buffers. Output at least one input cell from input queue using at least one Transmitting to a queue;   If at least one input cell is input queue if the requested request is rejected Delaying transmission to an output queue from the at least one input in the network. To control the flow of a given cell. 39. The cell count of all cells shared by all existing connections is Less than a first limit and associated with one of the at least one output queue. A first signal rejecting the request when the dynamic buffer count is greater than or equal to a second limit. And a second signal that stops forwarding the transmission request to one output queue. 39. The method of claim 38, further comprising asserting the other. 40. The traffic type cell count is less than the first limit and one output queue If the dynamic buffer count associated with the first signal is less than the second limit, Do not assert either of the second signals 40. The method of claim 39, further comprising a step. 41. If the traffic type cell count is greater than or equal to the first limit, the first signal 41. The method of claim 40, further comprising asserting. 42. Traffic type cell count is greater than or equal to the first limit and one output queue The first signal and the second signal if the dynamic buffer count associated with 42. The method of claim 41, further comprising asserting both of the signals. 43. The allocated buffer status count associated with one output queue is equal to the second limit. The traffic type cell count is greater than or equal to the first limit. When the buffer count is greater than or equal to the third limit, either the first signal or the second signal 43. The method of claim 42, further comprising the step of not asserting. 44. When the allocated buffer count is greater than or equal to the third limit, the first signal and 44. The method of claim 43, further comprising asserting both the first and second signals. 45. If the allocated buffer count is less than the third limit, but the allocated buffer count is Buffer status count is greater than or equal to the second limit, or traffic-type cell count is Assert the second signal, but assert the first signal when greater than or equal to one limit The method of claim 44, further comprising the step of not performing. 46. If the output queue has already sent the first signal, the first Further comprising the step of reasserting the signal of Item 46. The method according to Item 45.

────────────────────────────────────────────────── ─── Continuation of front page    (81) Designated countries EP (AT, BE, CH, DE, DK, ES, FI, FR, GB, GR, IE, IT, L U, MC, NL, PT, SE), OA (BF, BJ, CF) , CG, CI, CM, GA, GN, ML, MR, NE, SN, TD, TG), AP (KE, LS, MW, SD, S Z, UG), UA (AM, AZ, BY, KG, KZ, MD , RU, TJ, TM), AL, AM, AT, AU, AZ , BB, BG, BR, BY, CA, CH, CN, CZ, DE, DK, EE, ES, FI, GB, GE, HU, I L, IS, JP, KE, KG, KP, KR, KZ, LK , LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, R U, SD, SE, SG, SI, SK, TJ, TM, TR , TT, UA, UG, US, UZ, VN (72) Inventor Hauser, Stephen A             Massachusetts, United States             01803, Burlington, Farms Dora             Eve 106 (72) Inventors Manning, Thomas A             Massachusetts, United States             01532, Northborough, Summer Street               26th

Claims (1)

[Claims] 1. A plurality associated with a plurality of input ports forming at least one input queue Forms at least one output queue with the input buffer of In an exchange having an associated output buffer and in an input queue of an input memory Receiving the received at least one input cell;   Transmitting at least one incoming cell to the at least one output queue Forwarding the request;   Sufficient buffer in the output queue to receive at least one incoming cell Authorizing the transmission request if the key is available;   Sufficient buffer in the output queue to receive at least one incoming cell Rejecting the transmission request if the key is not available;   At least one input cell if the request issued is granted, Transmitting to the output queue from   If at least one input cell is entered queue if the request is rejected Delaying transmission to an output queue from the at least one input in the network. To control the flow of a given cell. 2. The step of receiving includes at least one of one of a plurality of input queues. Receiving the input cells of a plurality of output keys. The method of claim 1, further comprising transmitting to at least one of the queues. the method of. 3. The step of issuing the request comprises the step of sending each input cell to a respective output queue. When at least one incoming cell is received by the Each request is a transmission request that is specific to each input and output queue. 3. The method of claim 2, further comprising the step of exiting from each input queue. 4. Assign each input queue and output queue to the selected connection And flow control is performed on a per connection basis. The method of claim 3. 5. Assign each input queue and output queue to the selected service class 4. The method of claim 3, further comprising the step of: 6. Each input key for the selected connection and the selected service class Queue and output queue so that flow control is one 4. The method according to claim 3, wherein the processing is executed for each service class for each connection. Law. 7. Indicates whether the request was granted or rejected in response to a transmission request 4. The method of claim 3, further comprising providing a feedback message. 8. ACCEPT / REJECT message as part of feedback message Further comprising the step of providing a message, if the message indicates "ACCEPT", At least one input cell in at least one input queue has at least one At least one if transmitted to an output queue and the message indicates "REJECT" 8. The method of claim 7, wherein the message is not transmitted to the output queue of the message. 9. NO-OP / XOFF message as part of feedback message Receiving an XOFF from one of the plurality of output queues. Each input queue sends a transmission request to one of the output queues. 8. The method of claim 7, wherein said stopping. 10. For transmission from a single input queue to multiple output queues, a single input queue Multiple output queues so that transmission from a queue to multiple output queues takes place during the same period. ACCEPT / REJECT and NO of feedback message from -Performing a logical OR operation on the OP / XOFF portion. The method of claim 7. 11. For transmission from multiple input queues to a specific output queue, multiple input queues XOF to provide sufficient buffer for synchronous reception of transmissions from F Feedback message dynamically sets the threshold given by a particular output queue 10. The method of claim 9, further comprising the step of: 12. One of the multiple input queues to one of the multiple output queues One of the multiple output queues so that transmission requests can be Providing an XON message to one of the plurality of input queues. 10. The method of claim 9, comprising: 13. XON menu when dequeuing a cell from one of multiple output queues 13. The method of claim 12, further comprising providing a message. 14． Given when one of the output queues drops below a threshold Set a threshold in one of a plurality of output queues providing XON messages 14. The method of claim 13, further comprising the step of: 15. After a predetermined time has elapsed following the reception of the XOFF message, Providing a XON message to one of the input queues. The method according to claim 12. 16. XON for one of multiple input queues based on regular time 13. The method of claim 12, further comprising providing a message. 17． From one of the plurality of output queues to one of the plurality of input queues. 13. The method of claim 12, further comprising providing an XON message. 18. Queues contain buffers, which are organized into a number of individual cells at each hierarchical level. It further comprises the step of organizing into a hierarchy of levels with And provide feedback for each level based on combined flows 3. The method of claim 2. 19. Queues contain buffers, which are organized into a number of individual cells at each hierarchical level. Further comprising the step of organizing into a hierarchy of levels with 3. The method of claim 2, wherein feedback is provided to the user. 20. Controlling the flow of at least one data unit in a telecommunications network An exchange,   At least one input port for receiving a data unit input from a telecommunications network; And   At least one output port for transmitting data units from the switch;   Temporarily input data units received at each input port At least one input port associated with the at least one input port for temporarily storing With the buffer queue,   The input data units received from the respective input buffer queues are temporarily stored. At least one associated with the at least one input buffer queue for temporarily storing Output buffer queue, and   For the at least one input buffer queue, the at least one input buffer Buffer queue from one of the buffer queues to a particular output buffer queue. A first state indicating an authorization of permission to transmit the data unit; From one of the output buffer queues to the at least one output buffer queue. A second indicating a denial of permission to transmit at least one data unit to one of the second At least operable to provide the feedback message having a status An exchange comprising one feedback message generator. 21. At least one data unit to the at least one input buffer key; From the one of the at least one output buffer queue to the one of the at least one output buffer queue. At least one transmission request operable to request permission to transmit to at least one Further comprising a generator, wherein the at least one feedback message generator comprises Feedback message in response to a request from at least one transmission request generator 15. The switch of claim 14, wherein 22. 16. A feedback message generator for each input port. The exchange described. 23. Each connection uses a single input queue and a single output queue, The flow control according to claim 15, whereby the flow control is performed for each connection. switch. 24. Each input queue and each output queue are assigned to the selected service class 2. The method according to claim 1, wherein the flow control is performed for each service class. 6. The exchange according to 6. 25. Each input queue and each output queue is Assigned to one service class, so that flow control is 17. The exchange according to claim 16, which is executed for each service and one service class. 26. Feedback indicating whether the request was granted or denied 17. The switch of claim 16, wherein a message is provided in response to the transmission request. 27. Feedback message is ACCEPT / REJECT message And if the message indicates "ACCEPT" in at least one input queue At least one incoming cell is transmitted to at least one output queue and the If the message indicates "REJECT", it shall not be transmitted to at least one output queue. An exchange according to claim 20. 28. The feedback message includes a NO-OP / XOFF message, Each input queue that receives XOFF from one of the multiple output queues has multiple output queues. The method of claim 20, further comprising: stopping issuing a transmission request to one of the force queues. switch. 29. For transmission from a single input queue to multiple output queues, a single input queue The transmission from a queue to a plurality of output queues is performed such that the transmission is performed serially and synchronously. Feedback message from force queue For each ACCEPT / REJECT and NO-OP / XOFF part 21. The switch of claim 20, further comprising a circuit for performing a logical OR operation. 30. For transmission from multiple input queues to a specific output queue, multiple input queues XOF to provide sufficient buffer for synchronous reception of transmissions from Dynamically adjust F feedback message given by specific output queue 23. The switch of claim 22, wherein a possible threshold is increased. 31. One of the multiple input queues to one of the multiple output queues One of the plurality of output queues to again enable transmission requests to be issued. Provide an XON message to one of the plurality of input queues from An exchange according to claim 22. 32. The XON message decodes cells from one of the output queues. 26. The switch of claim 25, provided when queuing. 33. Given when one of the plurality of output queues drops below a threshold. Threshold in one of the plurality of output queues to provide an XON message. 27. The switch of claim 26, wherein a value is set. 34. After a predetermined time has elapsed following receipt of the XOFF message, the 3. The XON message is provided to one of a number of input queues. The exchange according to 5. 35. One of the plurality of input queues based on a regular time 26. The switch of claim 25, wherein the XON message is provided to the switch. 36. XO from one of the plurality of output queues to a plurality of input queues The switch of claim 25, wherein N messages are provided. 37. The queue includes a buffer, the buffer comprising a number of individual It is arranged in a hierarchy of levels with cell flows, and the feedback is at each level. 2. Provided for each level based on the combined flows in the level The exchange according to 5. 38. The queue includes a buffer, the buffer comprising a number of individual It is arranged in a hierarchy of levels with the flow of cells, and the feedback is applied to each individual flow. 16. The switch of claim 15, provided for a row. 39. A plurality of input buffers associated with at least one input queue; And a plurality of output buffers associated with one output queue. Receiving at least one input cell received in an input queue of an input memory; Trusting stage,   Transmitting at least one incoming cell to the at least one output queue Forwarding the request;   Sufficient buffer in the output queue to receive at least one incoming cell Authorizing the transmission request if the key is available;   Sufficient buffer in the output queue to receive at least one incoming cell Rejecting the transmission request if the key is not available;   At least one input cell if the request issued is granted, Transmitting to the output queue from   At least one entered cell if the issued request is rejected Delaying the transmission from the input queue to the output queue. A method of controlling the flow of one input cell. 40. If the traffic type cell count is less than the first limit and the queue If the file count is less than the second limit, either REJECT or XOFF (dynamic) 40. The method of claim 39, further comprising the step of not asserting the offset. 41. If the traffic type cell count is less than the first limit and the dynamic queue If the buffer count is greater than or equal to the second limit, REJECT and XOFF (dynamic 40. The method of claim 39, further comprising the step of asserting both. 42. Traffic type cell count is greater than or equal to the first limit and dynamic queue If the fa count is less than the second limit, do not assert XOFF (dynamic) 40. The method of claim 39, further comprising asserting REJECT. 43. Traffic type cell count is greater than or equal to the first limit and dynamic queue If the file count is greater than or equal to the second limit, both REJECT and XOFF (dynamic) 40. The method of claim 39, further comprising the step of asserting 44. The buffer status count assigned to the queue is greater than the count limit and the traffic Queue type cell count is greater than the cell count limit and the buffer assigned to the queue When the count is above the count limit, either REJECT or XOFF (assignment type) 44. The method of claim 43, further comprising the step of not asserting 45. When the allocated buffer count of the queue is greater than or equal to the buffer count limit Asserting both REJECT, XOFF (allocation type) 44. The method of claim 43. 46. If the queue's allocated buffer count is less than the count limit, Whether the allocated buffer status count is greater than or equal to the count limit or a traffic-type cell When the count is above the cell count limit, REJECT is asserted but XOFF 44. The method of claim 43, further comprising the step of not asserting (allocated). 47. If the FSPP queue has already sent XOFF, X 47. The method of claim 46, further comprising reasserting OFF.