Fujitsu Corporation

Fujitsu Network Communications, Inc.

Other

3com Corporation

Synernetics Inc.

Stephen A Hauser

Thomas A Manning

Stephen A Caldara

Raymond L Strouble

Robert B McClure

Matthias L Colsman

Richard G Bubenik

Douglas H Hunt

Jay L Madnick

Alan D Sherman

David J Husak

Christopher P Lawler

Michael E Gaddis

Stephen L Van Seters

Mark A Sankey

David N Peck

Jeffrey L Williams

Stephen R Veit

James M Meredith

An Asynchronous Transfer Mode switch and method which facilitate priority arbitration of point-to-point and point-to-multipoint transmission are disclosed. To execute point-to-multipoint operation a bandwidth arbiter maintains a first list of connections and bit vectors indicating designated destination ports. The list maintained by the bandwidth arbiter is then compared to an unassigned output port bit vector to determine matches therebetween at which point-to-multipoint transmission may be made by utilizing instantaneously unused bandwidth within the switch. To execute point-to-point operation each input port maintains a list of connections associated with each output port, and those lists are used in conjunction with output port request information per input port in the bandwidth arbiter to match requests to the unassigned output port bit vector. The bandwidth arbiter may also assign priority to connections in the list.

Priority arbitration for point-to-point and multipoint transmission

An asynchronous transfer mode (ATM) based service consolidation switch ( ) includes an input/output module ( ) having a to-switch port (TSPP) processor ( ) and a from-switch port processor (FSPP) ( ). The TSPP ( ) and the FSPP ( ) communicate with a bandwidth arbiter ( ), multipoint topology controllers ( ), and a data crossbar ( ) on a switch control module ( ). The TSPP ( ) receives traffic over links for conversion into an internal cell format. Internal cells are buffered until allowed to transfer to an appropriate FSPP ( ). Multipoint topology controllers ( ) performs translations for internal switch flow control through interactions between the TSPPs ( ), FSPPs ( ), and the bandwidth arbiter ( ). The bandwidth arbiter ( ) performs appropriate bandwidth arbitration to allow internal cells to flow from TSPPs ( ) to FSPPs ( ) over the data crossbar ( ).

Asynchronous transfer mode based service consolidation switch

A method and apparatus for providing buffer state accounting at a link level, otherwise known as link flow control, in addition to flow control at the virtual connection level. Link flow control enables receiver cell buffer sharing while maintaining per-connection bandwidth with lossless cell transmission. High link level update frequency is enabled without a significant sacrifice in overall link forward bandwidth. A higher and thus more efficient utilization of receiver cell buffers is achieved.

Method and apparatus for providing buffer state flow control at the link level in addition to flow control on a per-connection basis

A system (,) is provided for identifying a processing port (,) and a link (,) at which a cell (,) is received. The system (,) includes a logical link table (,) having a plurality of logical link entries (,). Each logical link entry (,), which corresponds to a particular link (,) of a processing port (,) associated with the logical link table (,), specifies a numerical value. The processing port (,) may receive the cell (,) at one of a plurality of links (,). The processing port (,) can convert the cell (,) by replacing a numerical value of an identification field, such as a virtual channel identification field (,), of the cell (,) with the numerical value specified by the logical link entry (,) corresponding to the link (,) at which the cell (,) is received. A switch control module (,), which is connected to the processing port (,), may receive the converted cell (,). The switch control module (,) can identify the link (,) and the processing port (,) at which the cell (,) corresponding to the converted cell (,) was received by referencing a reverse mapping table (,) using the numerical value of the logical link entry (,) in the converted cell (,).

Port and link identification

A mechanism enabling plural queues in a downstream telecommunications network element to be treated as a single, joint queue for purposes of connection-level flow control. A pointer in at least one queue descriptor points to a queue descriptor in which is maintained a set of shared, joint counters. Other flow control elements are maintained individually with respect to each queue descriptor. This mechanism enables flow control elements associated with a single transmitter queue to flow control plural connections terminating in plural queues associated with a single receiver processor.

Joint flow control mechanism in a telecommunications network

An Asynchronous Transfer Mode switch and method which facilitate point-to-multipoint transmission are disclosed. Each input port within the switch includes a switch allocation table ('SAT') which manages bandwidth allocation and delay. Each SAT includes a plurality of sequentially ordered cell time slots, a subqueue and a synchronized pointer which is directed to one of the slots such that at any given point in time each of the pointers is directed to the same slot location in the respective SAT with which the pointer is associated. To execute point-to-multipoint operation where output port conflicts are present the switch transmits copies of the cell to the output ports at different points in time. More particularly, the switch transmits copies of the cell to available output ports, and tracks such transmission for managing future transmission to unserviced output ports. To track transmission the switch includes a map and scoreboard. The subqueues are used to index into a table and may be associated with one or more output ports. The map indicates which subqueues, and hence which output ports, are initially eligible to receive a copy of the cell. The scoreboard indicates which subqueues, and hence which output ports, have received a copy of the cell. Tracking is realized by updating the scoreboard when copies of cells are transmitted. Copies of the cell are not sent to already serviced output ports. When each designated subqueue has been service, and hence each associated output port has been serviced, the cell is dequeued.

Point-to-multipoint transmission using subqueues

In a link-level flow controlled system, a method and apparatus providing the ability to partition a buffer resource among multiple prioritized buffer subsets through definition of at least one threshold, the buffer resource being shared by a plurality of connections. Different category of service levels, in terms of delay bounds, are thus enabled. The presently disclosed link-level flow controlled system provides for zero cell loss. The shared buffer resource is divided among N priority pools, defined by N-1 threshold levels, each priority pool attributable to a respective category of service. Link-level counters and registers, disposed in a transmit element, as well as an indication of priority level associated with each connection, are employed in realizing the shared buffer resource.

Prioritized access to shared buffers

A method and apparatus for receiving and transmitting network frames via an internetworking device, in which a first portion of a total number of buffers is allocated among port-dedicated buffer pools, and a second portion is placed in a common pool accessible by any of the network ports. A frame is received at a first port, and a list of buffers accessible only by that port is referenced to identify buffers not already in use. A second list of buffers in the common pool is referenced to identify unused buffers for use if insufficient unused buffer space is available in the port-dedicated buffer pool. Frame data is then stored in the identified buffer(s). Upon retransmission, the buffer(s) used to store the. transmitted frame is released to the port-dedicated and/or common buffer pool(s).

Method and apparatus for internetworking buffer management

A method and apparatus for providing a minimum per-connection bandwidth guarantee and the ability to employ shared bandwidth thereabove in an environment having both virtual-connection and link-level flow control. A buffer pool downstream of a transmitter and disposed in a receiver is divided among a first portion dedicated for allocated bandwidth cell traffic and a second portion for dynamic bandwidth cell traffic. Link flow control enables receiver cell buffer sharing while maintaining the per-connection bandwidth guarantee. No cell-loss due to buffer overflows at the receiver is also guaranteed, resulting in high link-utilization in a frame traffic environment, as well as low delay in the absence of cell retransmission. A higher and thus more efficient utilization of receiver cell buffers is achieved.

Minimum guaranteed cell rate method and apparatus

Methods and apparatus for scheduling cell transmission over a network link by a switch. The switch includes a plurality of queues associated with each link. Lists of queues are maintained for each link. In one embodiment, each link is associated with more than one type of list (with the list type corresponding to a scheduling category) and more than one prioritized list of each type (with the priority of the list corresponding to a quality of service). The scheduling lists are accessed to permit cell transmission from a queue contained therein in a predetermined sequence as a function of scheduling category, priority within a particular scheduling category and whether the bandwidth requirement for the particular scheduling category has been met. With this arrangement, maximum permissible delay requirements for each scheduling category are met.

Network link access scheduling using a plurality of prioritized lists

A method and apparatus is disclosed for allocating bandwidth within a network switch having a plurality of input ports coupled to a plurality of output ports through a switch fabric to assure that a minimum bandwidth is allocated for predetermined scheduling lists. A switch allocation table is provided for each of a plurality of input ports. Each switch allocation table is organized as a circular table which is sequentially indexed via an associated index counter. Respective entries in the switch allocation table comprise scheduling list numbers which serve to identify cells requiring switch bandwidth. The respective index counters are synchronized such that all switch allocation tables have a corresponding entry selected. The amount of bandwidth and delay through the network switch is controlled for each of the scheduling lists based upon the number and spacing of entries in the respective switch allocation table. Latency through the network switch is significantly reduced via the use of a pace counter and a pace limit which, in cooperation with the switch allocation table, determine whether a cell associated with a particular scheduling list may be dispatched through the switch fabric for transmittal onto a network link by at least one of the output ports.

Controlling bandwidth allocation using a pace counter

An apparatus and a method are disclosed for arbitrating between streams of ATM cells, or sources for a connection, on multiple input port processors vying for an opportunity to be transmitted as a fixed bandwidth, or allocated, connection on a single output port through a network switch. The network switch maintains a plurality of input port processors, at least one output port, and input and output buffers associated with the respective input and output ports. Streams of ATM cells enter the network switch as sources for a connection through the multiple input port processors and are buffered in the input buffers. The ATM cells are then routed from the input buffers to an output buffer in the output port. The network switch also provides a multipoint topology controller (MTC) and a bandwidth arbiter (BA) for performing the arbitration.

Multipoint-to-point arbitration in a network switch

A communication device (10) includes a number of input/output modules (12) coupled to a switch control module (14) using an interconnect (40) and to a redundant switch control module (16) using a redundant interconnect (42). Each interconnect (40) and redundant interconnect (42) includes a control interconnect (44) and a data interconnect (46). The control interconnect (44) establishes control information for transferring a cell in the communication device (10) and the data interconnect (46) performs the cell transfer.

Growing community of inventors

Burlington, MA, United States of America

Stephen A Hauser