129 results about "Virtual Output Queues" patented technology

To avoid packet out-of-sequence problems, while providing good load balancing, each input port of a switch monitors the outstanding number of packets for each flow group. If there is an outstanding packet in the switch fabric, the following packets of the same flow group should follow the same path. If there is no outstanding packet of the same flow group in the switch fabric, the (first, and therefore subsequent) packets of the flow can choose a less congested path to improve load balancing performance without causing an out-of-sequence problem. To avoid HOL blocking without requiring too many queues, an input module may include two stages of buffers. The first buffer stage may be a virtual output queue (VOQ) and second buffer stage may be a virtual path queue (VPQ). At the first stage, the packets may be stored at the VOQs, and the HOL packet of each VOQ may be sent to the VPQ. By allowing each VOQ to send at most one packet to VPQ, HOL blocking can be mitigated dramatically.

The present invention describes a system for providing quality of service (QoS) features in communications switching devices and routers. The QoS provided by this system need not be intrinsic to the communication protocols being transported through the network. Preferred embodiments also generate statistics with the granularity of the QoS. The system can be implemented in a single application-specific integrated circuit (ASIC), in a chassis-based switch or router, or in a more general distributed architecture. The system architecture is a virtual output queued (VOQed) crossbar. The administrator establishes policies for port pairs within the switch, and optionally with finer granularity. Frames are directed to unique VOQs based on both policy and protocol criteria. Policies are implemented by means of a scheduling engine that allocates time slices (minimum units of crossbar access).

A traffic manager for a network switch input or output port stores incoming cells in a cell memory and later sends each cell out of its cell memory toward one of a set of forwarding resources such as, for example, another switch port or an output bus. Data in each cell references the particular forwarding resource to receive the cell. Each cell is assigned to one of several flow queues such that all cells assigned to the same flow queue are to be sent to the same forwarding resource. The traffic manager maintains a separate virtual output queue (VOQ) associated with each forwarding resource and periodically loads a flow queue (FQ) number identifying each flow queue into the VOQ associated with the forwarding resource that is to receive the cells assigned to that FQ. The traffic manager also periodically shifts an FQ ID out of each non-empty VOQ and forwards the longest-stored cell assigned to that FQ from the cell memory toward its intended forwarding resource. The traffic manager separately determines the rates at which it loads FQ IDs into VOQs and the rates at which it shifts FQ IDs out of each non-empty VOQ. Thus the traffic manager is able to separately control the rate at which cells of each flow queue are forwarded and the rate at which each forwarding resource receives cells.

Configurable virtual output queues (VOQs) in a scalable switching system and methods of using the queues are provided. The system takes advantage of the fact that not all VOQs are active or need to exist at one time. Thus, the system advantageously uses configurable VOQs and may not dedicate memory space and logic to all possible VOQs at one time.

A system and a method to avoid packet traffic congestion in a shared memory switch core, while dramatically reducing the amount of shared memory in the switch core and the associated egress buffers and handling unicast as well as multicast traffic. According to the invention, the virtual output queuing (VOQ) of all ingress adapters of a packet switch fabric are collapsed into its central switch core to allow an efficient flow control. The transmission of data packets from an ingress buffer to the switch core is subject to a mechanism of request/acknowledgment. Therefore, a packet is transmitted from a virtual output queue to the memory shared switch core only if the switch core can send it to the corresponding egress buffer. A token based mechanism allows the switch core to determine the egress buffer's level of occupation. Therefore, since the switch core knows the states of the input and output adapters, it is able to optimize packet switching and to avoid packet congestion. Furthermore, since a packet is admitted in the switch core only if it can be transmitted to the corresponding egress buffer, the shared memory is reduced.

A packet switching system and method are disclosed. The system includes a plurality of input and output ports and an input buffer at each of the input ports. The system further includes an input scheduler associated with each of the input buffers and a centralized memory shared by the output ports. An output buffer is located at each of the output ports and an output scheduler is associated with each of the output ports. Each of the input buffers comprises a plurality of virtual output queues configured to store a plurality of packets in a packed arrangement.

A method of providing virtual output queue feedback to a number of boards coupled with a switch. A number of virtual queues in the switch and/or in the boards are monitored and, in response to one of these queues reaching a threshold occupancy, a feedback signal is provided to one of the boards, the signal directing that board to alter its rate of transmission to another one of the boards. Each board includes a number of virtual output queues, which may be allocated per port and which may be further allocated on a quality of service level basis.

A pipelined scheduling system allowing suppressed unfairness among inputs and reduced fixed delay time is disclosed. Virtual output queues (VOQs) for each input port corresponding to respective ones of the output ports are stored. The VOQs are equally divided into a plurality of groups. Scheduling modules each corresponding to the groups performs a scheduling operation at a single time slot in a round robin fashion such that each of the scheduling modules reserves output ports at a predetermined future time slot for forwarding requests from logical queues of a corresponding group based on a reservation status received from a previous scheduling module, and then transfers an updated reservation status to an adjacent scheduling module. A crossbar switch connects each of the input ports to a selected one of the output ports depending on the reservation status at each time slot.

Various embodiments of a virtual output queue system within a network element enables per-input port virtual output queues within a network data processor of the network element. In one embodiment, each port managed by a network data processor has an associated set of virtual output queues for each output port on the network data element. In one embodiment, network data processor hardware supports per-processor VOQs and per-input port VOQs are enabled in hardware for layer 3 forwarding by overloading layer 2 forwarding logic. In such embodiment, a mapping table is generated to enable virtual per-input port VOQs for layer 3 forwarding logic using layer 2 logic that is otherwise unused during layer 3 forwarding. In one embodiment, multiple traffic classes can be managed per-input port when using per-input port VOQs. In one embodiment, equal cost multi-path (ECMP) and link aggregation support is also enabled.

A queuing mechanism is presented that allows port data and processor data to share the same crossbar data pathway without interference. An ingress memory subsystem is dividing into a plurality of virtual output queues according to the switch destination address of the data. Port data is assigned to the address of the physical destination port, while processor data is assigned to the address of one of the physical ports serviced by the processor. Different classes of service are maintained in the virtual output queues to distinguish between port data and processor data. This allows flow control to apply separately to these two classes of service, and also allows a traffic shaping algorithm to treat port data differently than processor data.

A packet switching system arbitrates between Virtual Output Queues (VoQ) in plural input buffers, so as to grant the right of transmitting data to a crossbar switch to some of the VoQs by taking both an output data interval of a VoQ and the queue length of a VoQ as parameters. The system suppresses the delay time of the segment of a VoQ having a high load, thereby preventing buffers from overflowing; and, also, the system permits a VoQ having a low load to transmit segments under no influence of the VoQ that has a high load and is just reading out the segment.

A multiple phase cell dispatch scheme, in which each phase uses a simple and fair (e.g., round robin) arbitration methods, is described. VOQs of an input module and outgoing links of the input module are matched in a first phase. An outgoing link of an input module is matched with an outgoing link of a central module in a second phase. The arbiters become desynchronized under stable conditions which contributes to the switch's high throughput characteristic. Using this dispatch scheme, a scalable multiple-stage switch able to operate at high throughput, without needing to resort to speeding up the switching fabric and without needing to use buffers in the second stage, is possible. The cost of speed-up and the cell out-of-sequence problems that may occur when buffers are used in the second stage are therefore avoided. A hierarchical arbitration scheme used in the input modules reduces the time needed for scheduling and reduces connection lines.

The technical proposal comprises: the parallel interchange box consists of N input controllers, m Crossbar interchange boxes with low speed input buffer and N output controllers. Each input controller contains N virtual output queues and a load divider. The virtual output queue is cell buffer used to save input cell. The load divider is used for keeping load balance and determining the cell sent to Crossbar interchange box in each time slot, and is composed of a cell dividing request generator, a Crossbar state monitor, an input polling pointer generator and a cell dividing arbitration logic. Each output controller comprises mN virtual input queues and a cell integrator. The virtual output queue is a cell buffer. The cell arriving at the output controller firstly queues at the virtual output queue. The cell integrator rearranges the cells and is composed of cell rearrangement request generator, output polling pointer generator and cell rearrangement arbitration logic.

The invention discloses a two-level switch-based load balanced scheduling method, which comprises the following steps that first-level input ports buffer arriving cells in a virtual output queue (VOQ) according to destination ports; a scheduler switches messages to second-level input ports through a first-level switching network, wherein k cells from the same stream in the VOQ are called unit frames; each first-level input port executes minimum length scheduling according to a traffic distribution matrix, and transmits the unit frames of the same stream to a fixed mapping area of the stream through the first-level switching network in k continuous external timeslots; and N second-level input ports are sequentially divided into N/k groups of which each comprises k continuous second-level input ports forming an area, and each area buffers the cells in an output queue (OQ) according to the destination ports, and switches the cells to the destination output ports through a second-level switching network. The method has the advantages that a scheduling process is simple, computation or communication is not required, the method is easily implemented by hardware, the throughput of 100 percent is ensured, the sequence of the messages can be ensured, and the like.

The invention discloses a scheduling method, device and system of a data exchange network. According to the embodiment of the invention, input port equipment is used for measuring a VOQ (Virtual Output Queue), and then a request bandwidth is calculated according to a measured result. Compared with the method for determining the request bandwidth by taking a priority level of a data flow according to the cache state of the data flow in the prior art, the method for calculating the request bandwidth has the advantages that the current state of the data flow can be more accurately reflected, so that the data scheduling between the input port equipment and the VOQ can be more reasonable and effective, and the data scheduling can be adapted to the actual state of the current network. Therefore, the scheduling method, device and system of the data exchange network can be more suitable for a large-sized, high-speed and long-distance exchange network.