Abstract: A communication network with a database consistency mechanism is disclosed, wherein a sequence number and a set of routing information for each of a set of virtual circuits of the communication network are maintained in a main database and an auxiliary database in each of a set of communication nodes in the communication network. The sequence numbers in the main database or the auxiliary database in each of the communication nodes are verified if one of the communication nodes switches between the main database and the auxiliary database, and then virtual circuits are rerouted when necessary.

Abstract: An asynchronous transfer mode inverse multiplexed communication system is disclosed wherein a series of communication cells are multiplexed over a set of communication links. Each communication cell includes a framing bit of a predetermined framing bit stream for each communication link and a control channel bit of a control message for each communication link. Inbound communication cells from each communication link are aligned according to the corresponding framing bit stream. The control message specifies an ordered list of logical identifiers to indicate a multiplexed sequence of transfer of the communication cells over the communication links.

Abstract: To simplify the service decision made in a queue based digital switch, a method and apparatus is introduced that makes service decisions based upon the history of incoming cells. The apparatus includes a minimum service rate circuit that monitors the rate of arriving cells. The minimum service rate circuit tests the arriving cells to determine if they are in conformance with the minimum service rate of a service contract. The minimum service rate circuit may use a continuous state leaky bucket algorithm as specified in the CCITT Recommendation I.371 document, dated 1992, to determine if a cell is in conformance with the minimum service rate of the service contract. When a cell arrives that conforms to the minimum service rate, the minimum service rate circuit notifies the server and the server serves the queue associated with the connection.

Abstract: A method for performing rate control for digital communication systems. A server serves N connection queues where each connection queue has accumulation rate a.sub.i. Each credit accumulation rate a.sub.i is divided into a set of binary coefficients. The connections are then divided into connection groups wherein each connection group has group accumulation rate created using the binary coefficients. The connection group accumulation rate is used to maintain a group credit balance c.sub.j. To select a connection to be served, the server examines the group credit balances and selects the group with the greatest credit balance. A connection within the selected group is chosen using a round-robin system. Thus the server selects a connection to serve without performing a linear scan over all the connections.

Abstract: A mechanism for routing a communication cell in a cell switching communication controller that employs multiple path identifier masking functions selected by a header control field in the communication cell and that employs a content addressable memory comprising a plurality of entries, wherein each entry stores a pre configured local termination identifier and a pre configured pass through identifier.

Abstract: A method and apparatus for exchanging communication cells in a communication controller, wherein an arbiter determines transmission requests for each of a plurality of communication modules in the communication controller. Each communication module has a transmit signal line and a receive signal line coupled to a switching circuit in the communication controller. The arbiter selectively couples the transmit signal lines to the receive signal lines according to the transmission requests. The communication modules transmit communication cells through the switching circuit, while the arbiter determines new transmission requests from each communication module.

Abstract: A mechanism for buffering communication cells in a communication controller, wherein a cell queuing circuit provides a cell loss priority mechanism, and wherein the cell queuing circuit determines service states for queue channels according to bandwidth allocation parameters. The service states includes a serve.sub.-- now state, a serve.sub.-- ok state, and a no.sub.-- serve state, such that a queue channel is in the serve.sub.-- now state if the queue channel must be serviced to maintain a minimum information rate parameter for the queue channel, the serve.sub.-- ok state if the queue channel can be serviced and not exceed a peak information rate parameter for the queue channel.

Abstract: A method and apparatus for use in a cell network node for initial routing and rerouting of connections to a slave node based on ordering candidate slave connections, searching existing connections for candidate best routes and validating the selected best route comparing actual route delays and available bandwidth with maximum allowable delays and loading of the candidate slave connection. The invention also provides for programmable queuing delays by controlling queue lengths and for improved justification of reassembled information using actual maximum node delays.

Abstract: A feedback control system for congestion prevention in a cell (packet) switching communication network is described. Congestion control is accomplished by controlling the transmission rate of bursty traffic in the presence of high priority, voice, low speed statistical, high speed deterministic and multicast data. Because bursty traffic is relatively insensitive to delay, adequate buffer capacity can be provided at the network nodes in order to minimize bursty data cell loss. By monitoring the buffer queue lengths at the nodes, a control signal can be generated at each intermediate node indicating the state of congestion. Excess queue length indicates incipient congestion while short queue lengths indicate excess capacity. Queue status is forwarded to the destination node where it is interpreted and sent back to the source node as a feedback rate control signal using a 2-bit code.

Abstract: Virtual circuits are routed and grouped into virtual paths during an interactive topology design process. Virtual circuits are assigned to virtual paths that provide minimum cost to each pass through a topology design. Virtual paths are dispersed into subgroups that minimize bandwidth consumption and maximize routing flexibility. This topology optimization process is constrained to minimize use of network resources.

Abstract: A method and apparatus for aligning a digital communication data stream across a cell network, wherein plurality of timeslot samples are generated by sampling the digital communication data stream transferred over a first circuit-switching communication link. The timeslot samples are assembled into a series of communication cells in a bit or byte skewed arrangement. An align flag in the header of a communication cell indicates that the communication cell contains an aligned timeslot sample.

Abstract: A packet voice/data communication system provides a frequency measurement isochronous clocking transmission capability. This is a method of transferring clock information by directly measuring the frequency of the clock relative to a reference and then reproducing that exact clock frequency at the far end relative to the reference which has been carried through the system.

Abstract: A method and apparatus for converting a signal by reading a first signal that is represented in a first format. The first signal is used as an index into a lookup table, the first table containing entries representing signals in a second format modified by a gain. The first table outputs a second signal responsive to the index provided by the first signal, wherein the second signal is represented in a second format.

Abstract: A method of fair queuing and servicing cell traffic in a telecommunication node which interfaces with a telecommunication system including a multiplicity of nodes is described. The steps include placing cells of traffic are placed in a queue according to a hopcount associated with each cell of bursty traffic, the hopcount being representative of the number of nodes traversed by the associated cell. Cells of traffic within the queue are serviced according to their associated hopcount. The hopcount associated with each cell of traffic is incremented as each cell of traffic is serviced. Circuitry providing fair queuing and servicing of cell traffic in a telecommunication node which interfaces with a telecommunication system including a multiplicity of nodes is also described.

Abstract: Packets transported over a serial data stream need to have their start and stop information encoded so that they can be parsed by the receiving device. Techniques used in various standards require extra bandwidth to carry this information. For framed data streams like T1, proprietary protocols have used the frame structure to mark packet boundaries. Both types of solutions are desirable for unframed, long distance data streams like the CCITT G.703 2.048 Mbps unframed service, subrate trunks, or fractional T1 services. The present invention provides a packet framing method that uses the Cyclic Redundancy Check (CRC) found in most packet formats. The protocol does not require any extra bandwidth and can work with any serial data stream physical layer.

Abstract: A packet format for accurately transporting signaling information in a packet network is described. The packet format comprises a burst count, a sequence number, a burst time, and a signaling status bit. The burst count is for indicating a burst to which the packet belongs. The sequence number is for identifying a first packet of the burst. The burst time is for selectably indicating (1) a time delay from onset to a packet node bus for the first packet of the burst and (2) a time interval between successive signaling bit transitions.

Abstract: Packets transported over a serial data stream need to have their start and stop information encoded so that they can be parsed by the receiving device. Techniques used in various standards require extra bandwidth to carry this information. For framed data streams like T1, proprietary protocols have used the frame structure to mark packet boundaries. Both types of solutions are undesirable for unframed, long distance data streams like the CCITT G.703 2.048 Mbps unframed service, subrate trunks, or fractional T1 services. The present invention provides a packet framing method that uses the Cyclic Redundancy Check (CRC) found in most packet formats. The protocol does not require any extra bandwidth and can work with any serial data stream physical layer.

Abstract: A method and apparatus for stably maintaining an output clock signal from a phase-locked loop (PLL) frequency multiplier when switching from one clock source to another clock source is described. This method and apparatus maintains the phase relationship between the external signal to the phase detector and the feedback signal from the divider to the phase detector.

Abstract: A data communication system includes a repetitive pattern packet suppression technique which suppresses transmission of entire packets in a data stream when a repeating pattern has been established in the previous packet and then is found to repeat throughout the following packets. An expansion part of the technique fills the resulting hole in the data stream with the last pattern from the previously received packet.

Abstract: A packet communications network and apparatus for communicating information in voice and data packets transmits and receives voice and data in accordance with standardized frames of a standardized communications format such as a standard DS-1 type trunk. An apparatus is coupled to multiplex standardized channels into a single channel wherein voice or data signals are packetized into independently addressable packets synchronized on, for example, the DS-1 frame. The network includes voice and packet data concentration apparatus operable in a multiple node trunk environment to concentrate signals into independently addressable synchronously switchable packets, thereby to provide an efficient (high density capacity) interface between trunk terminations. Up to four times as much information can be transferred between nodes with the ability to switch between nodes as compared to conventional TDM and PCM communication without compression without the ability to switch between nodes.