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: Method and apparatus for extending lower-layer flow control end-to-end, transparent to network host systems, between network hosts attached to legacy networks without requiring any changes to the host networks or hosts themselves. In a first embodiment, a source host and a destination host, each residing on a respective LAN, communicate via an intermediate network supporting the lower-layer flow control. A higher-layer, end-to-end flow control protocol exists between the hosts. The lower-layer flow control protocol accounts for loss of bandwidth between each hop within the intermediate network. To extend the lower-layer flow control protocol to the hosts, an intelligent edge device of the intermediate network adjusts observed higher-layer flow control parameters based upon the state of the lower-layer flow control. No modifications to the legacy network or hosts is required, and the extension of flow control is transparent to the legacy networks.

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 ring trip detector has a voltage difference detector with first and second inputs, for supplying an off-hook signal upon detection of a voltage difference. The ring trip detector also has a switch extending between the first and second inputs of the voltage difference detector. The ring trip detector detects when a telephone current starts to flow through a sensing resistor having first and second ends and to a telephone set. The switch closes upon an initial current flow through the sensing resistor and then opens. The ring trip detector has a pulse generating mechanism having two inputs respectively connected to the first and second ends of the sensing resistor. The pulse generating mechanism has an output and generates a pulse at the output when current starts to flow through the sensing resistor. The switch has a trigger connected to the output of the pulse generating mechanism for closing the switch when the pulse is generated. A differentiator mechanism may be used as the pulse generating mechanism.

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: A method is disclosed for facilitating multicast operation in a network in which a data unit is multicast from a root node to a plurality of leaves via a plurality of branching point nodes in response to feedback processed at each branching point node. At least one cell forwarding technique is selected from a plurality of cell forwarding techniques at the respective branching point nodes. The cell forwarding techniques facilitate multicast operation by controlling forwarding and discard of multicast cells. The forwarding techniques are realized via use of a buffer ring in which cells are stored prior to forwarding. Manipulating head and tail pointers associated with the buffer ring allows for a plurality of desirable forwarding techniques.

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 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 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 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: The present invention relates generally to protection of asynchronous transfer mode (ATM) traffic against Synchronous Optical Network (SONET) fiber cuts or other types of transmission media failures in a SONET Ring. The nodes of the Synchronous Optical Network protect the asynchronous transmission mode cells for immediate failures in the Synchronous Optical Network by establishing a table indicating the topology of the nodes in the Synchronous Optical Network. Each node is capable of detecting a loss of header error check synchronization and generating a protection payload data unit, which is egressed to the plurality of nodes. In addition, each node is capable of ingressing protection payload data units from neighboring nodes and for switching the transmission of asynchronous transmission mode cells within the node so that the cells being transmitted in the network are protected.

Abstract: A circuit board enclosure for housing a plurality of circuit boards has a polymer casing having upper and lower openings and an interior. The circuit board enclosure also has upper and lower heat conductive pieces formed of a metal and fitting respectively within the upper and lower openings in the casing, in a water tight sealed relationship with the casing. The upper and lower heat conductive pieces have heat transfer fins protruding from the openings in the casing. The upper and lower heat conductive pieces have an interior side facing the interior of the enclosure. The interior sides have guide grooves to receive opposing sides of the circuit board. The guide grooves of the upper and lower heat conductive pieces are substantially parallel. The polymer casing may be formed of polycarbonate. The upper and lower heat conductive pieces may be formed of aluminum.

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.