Abstract: A system (10) is provided for identifying a processing port (12) and a link (22) at which a cell (24) is received. The system (10) includes a logical link table (14) having a plurality of logical link entries (30). Each logical link entry (30), which corresponds to a particular link (22) of a processing port (12) associated with the logical link table (14), specifies a numerical value. The processing port (12) may receive the cell (24) at one of a plurality of links (22). The processing port (12) can convert the cell (24) by replacing a numerical value of an identification field, such as a virtual channel identification field (28), of the cell (24) with the numerical value specified by the logical link entry (30) corresponding to the link (22) at which the cell (24) is received. A switch control module (18), which is connected to the processing port (12), may receive the converted cell (38).

Abstract: A constant phase crossbar switch system which avoids phase discontinuities at the outputs of the crossbar switch. The crossbar switch system includes input logic, a crossbar switch, output logic and a phase locked loop. The phase locked loop is used to generate a high speed internal clock from a system clock. High speed serial data streams transmitted at the internal clock frequency are received from corresponding transmitters and are coupled to the input logic. The input logic generates multiple versions of each serial data stream, one of the versions being undelayed and the other versions delayed by some fraction of a bit time. State machines are employed to selects the version of the serial data stream which results in the data stream data window being generally centered with respect to the high speed internal clock. The selected version of the data stream is employed as the active input to the crossbar switch.

Abstract: An encoder/decoder is disclosed which is operative to convert an 8 bit value to a ten bit serial run length limited code for transmission over a serial data link. The encoding technique maintains DC balance within 2 bits over a single ten bit word and compensates for DC imbalance by inverting selected words in the transmission sequence to correct for a DC imbalance resulting from the transmission of a prior unbalanced word. One or more encoding lookup tables are employed at the encoder to map each byte into a ten bit run length limited code for serialization and transmission over the serial data link. A second decoding lookup table is employed at the decoder to map the received 10 bit run length limited code into the original 8 bit value.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A system is disclosed for eliminating cell loss through the use of flow control of both allocated and dynamic bandwidth. When output buffers in the switch become filled to a predetermined threshold level a feedback message is provided to input buffers to prevent transmission of cells from the input buffers to the output buffers. In order to provide connection and traffic type isolation the buffers are grouped into queues and flow control may be implemented on a per queue basis. The feedback message is a digital signal including an ACCEPT/REJECT message and a NO-OP/XOFF message. An XOFF message can be received while transmitting via allocated bandwidth or dynamic bandwidth. In particular, an XOFF (allocated) message may be received with regard to allocated bandwidth and an XOFF (dynamic) message may be received with regard to dynamic bandwidth. When ACCEPT is received by the requesting input queue the cell is transferred to the output queue.

Abstract: 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.

Abstract: A switch control module (16) is provided for converting between an internal cell (23) and a first standard asynchronous transfer mode cell (34) and second standard asynchronous transfer mode cell (36). The internal cell (23) includes an internal header (42), payload information (44), and miscellaneous information (46). The first standard asynchronous transfer mode cell (34) includes the internal header (42) and miscellaneous information (46) of the internal cell (23). The second standard asynchronous transfer mode cell (36) includes the payload information (44) of the internal cell (23).

Abstract: An apparatus and a method are disclosed for unencumbering valuable switching resources in a network switch involved in a multipoint-to-multipoint switching scenario. The network switch includes an input processing port that is connected to a plurality of input links, and an output processing port that is connected to a plurality of output links. A data cell received on an input link is processed by the input processing port by appending a link number, a port number, and a connection identification code associated with the input processing port to the data cell. The data cell is then transferred to the output processing port where it is processed by comparing the appended link number, port number, and connection identification code with those associated with the output processing port. The data cell is then stored in a data buffering queue in the output processing port according to a matching scheme.

Abstract: A network switch utilizing centralized and partitioned memory for storing connection topology information. The switch includes at least one input port, at least one output port and a central switch fabric interconnecting the input port and output port, with the connection topology memory centralized at the switch fabric. The central switch fabric includes at least one input side translator associated with a predetermined number of input ports and at least one output side translator associated with a predetermined number of output ports. The connection topology memory is distributed among the at least one input side translator and the at least one output side translator. With this arrangement, memory bandwidth requirements associated with connection topology look-up operations are distributed and scaling the number of ports is facilitated.

Abstract: A redundant switch (50) is provided for performing a switch fabric test. The redundant switch (50) includes a foreground switch fabric controller (24) for controlling a foreground switch fabric (26), a background switch fabric controller (124) for controlling a background switch fabric (126), and a first I/O module (14) in communication with the foreground switch fabric controller (24). The first I/O module (14) sends, at the request of the foreground switch fabric controller (24), a test cell to an input of the background switch fabric (126) and receives the test cell from a corresponding output of the background switch fabric (126). The first I/O module (14) determines if an error occurred and provides an error signal to the foreground switch fabric controller (24) in response if an error occurred. The foreground switch fabric controller (24) may log the error signal or enable an alarm or indicator in response.

Abstract: A system (10) is provided for mapping a data cell (32) in a communication switch. The system (10) includes a virtual translation table (40) having at least one virtual path translation table queue entry (92) and at least one virtual channel translation table queue entry (90). A to-switch port processor (12), which can access the virtual translation table (40), has at least one link (16-30) which receives the data cell (32). The to-switch port processor (12) maps the received data cell (32) to a queue descriptor using the virtual translation table (40).