Abstract: A router for switching data packets from a source to a destination in a network in which the router includes a distributed memory. The distributed memory includes two or more memory banks. Each memory bank is used for storing uniform portions of a data packet received from a source and linking information for each data packet to allow for the extraction of the uniform portions of a data packet from distributed locations in memory in proper order after a routing determination has been made by the router.

Abstract: A packet switching system capable of ensuring the sequence and continuity of packets and further compensating for delays in transmission is disclosed. Each of two redundant switch sections has a high-priority queue and a low-priority queue for each of output ports. A high-priority output selector selects one of two high-priority queues corresponding to respective ones of the two switch sections to store an output of the selected one into a high-priority output queue. A low-priority output selector selects one of two low-priority queues corresponding to respective ones of the two switch sections to store an output of the selected one into a low-priority output queue. The high-priority and low-priority output selectors are controlled depending on a system switching signal and a packet storing status of each of the high-priority and low-priority queues.

Abstract: Methods and apparatus, including computer program products, implementing and using techniques for processing a data packet in a packet forwarding device. A data packet is received. A virtual local area network destination is determined for the received data packet, and a set of rules associated with the virtual local area network destination is identified. The rules are applied to the data packet. If a virtual local area network destination has been determined for the received data packet, the data packet is output to the destination, using the result from the application of the rules. If no destination has been determined, the data packet is dropped. A security system for partitioning security system resources into a plurality of separate security domains that are configurable to enforce one or more policies and to allocate security system resources to the one or more security domains, is also described.

Abstract: A fabric request controller implements flow control for data cells to a network or switch fabric. The fabric request controller issues request messages to the fabric switch and receives back corresponding grant messages. The fabric request controller includes a credit counter for metering the number of allowable outstanding requests. A fake request vector component periodically issues fake requests to compensate for information loss on the switch fabric.

Abstract: In general, the invention facilitates diagnosing fault conditions, such as flapping, by permitting users to request information for specific components in a network device such as a router. The invention also facilitates the diagnosis of other fault conditions, including, but not limited to, excessive numbers of dropped packets, hard drive crashes, high temperature readings, and inactive interface cards. A user may obtain a targeted log containing information relating to selected fault conditions or other network device events, rather than a system log containing information relating to all network device events, some of which may not be of interest to the user. The targeted log may be parsed and analyzed with greater ease than the system log.

Abstract: A cell disposal avoidance system is provided that can avoid disposal of the cells resided in the QoS buffer when a traffic of a specific QoS class in an ATM switch increases. The ATM switch includes a storage cell number monitor, a software data section 813, and a software controller 812. The storage cell number monitor monitors congestion of plural QoS buffers in the buffer 3, 5. The software data section 813 stores a cell reading priority (WRR value) attached for each QoS buffer. The software controller 812 dynamically changes the WRR value when congestion of a QoS buffer is in a congestion state (at generation of cell disposal or buffer congestion alarm) and increases the WRR value of the QoS buffer in a cell disposal state. Cells are divided in a time division mode according to the weight of the WRR value and read in a round format from the QoS buffer. The ATM switch resets the WRR value to an initial value when the congestion of the QoS buffer ceases.

Abstract: A router receives destination address information for a packet and determines, among entries in a first forwarding table, a closest match for the received destination address information. The router receives a pointer to a second forwarding table in accordance with the closest match determined in the first forwarding table and determines, among entries in the second forwarding table, a closest match for the received destination address information.

Abstract: An improved firewall for providing network security is described. The improved firewall provides for dynamic rule generation, as well using conventional fixed rules. This improvement is provided without significant increase in the processing time required for most packets. Additionally, the improved firewall provides for translation of IP addresses between the firewall and the internal network.

Abstract: A system controls the transfer of data. The system receives a request to transfer data and determines whether a counter value equals or exceeds a threshold. The counter value represents an amount of time since a previous data transfer. When the counter value equals or exceeds the threshold, the system transmits the data. In another implementation, the system tracks the amount of data read from a buffer. The system reduces the speed at which data is read when the amount of data read from the buffer exceeds a threshold.

Abstract: The invention provides a device (D2) for reducing ingress noise in a digital signal, comprising a noise predictor (20) for predicting an amount of ingress noise in the digital signal (sn) based on past samples of the ingress noise, and a subtractor (21) for subtracting the predicted amount of ingress noise from the digital signal. Channel distortion is compensated for by a noise-independent equalizer (25), such as a ZF equalizer, placed upstream of the noise predictor (20). The device (D2) may be incorporated, for example, in a cable modem termination system (CMTS) of an hybrid fiber/coax (HFC) network.

Abstract: A cross-bar switch includes a set of input ports for receiving data packets and a set of sink ports for transmitting the received packets to identified targets. A set of data rings couples the input ports to the sink ports. Each sink port utilizes the set of data rings to accept data packets targeted to destinations supported by the sink port. The cross-bar switch includes a multi-sink port for supporting explicit multicast addressing. The multi-sink port is coupled to each data ring and each sink port. The multi-sink port snoops multicast packets on the cross-bar switch's rings and transfers each packet to a set of sink ports that support the packet's targeted destinations.

Abstract: A device and method are disclosed for correctly restoring a read clock when there are a plurality of STM data stream transmission sources. In a CES device of an ATM communication system, ATM cells from respective connections, which are to be delivered to the same outgoing line, are accumulated in a reassembly buffer memory and a PLO control unit aggregates the amount of ATM cells accumulated in the reassembly buffer memory for each connection. Subsequently, the PLO control unit calculates the frequency of a read clock based on the amount of accumulated ATM cells for each connection. A PLO restores the read clock which is applied to read data from the reassembly buffer memory for delivery to an STM network.

Abstract: In a cable modem system, increasing or decreasing the rate of an MPEG Transport Stream involves two separate, but related, tasks: 1) incorporating a sufficient number of additional packets (or discarding packets) to make up for the difference in data rates between input and output, and 2) altering timing information (for instance, PCR (Program Clock Reference) values) present in some incoming packets to reflect their altered positions in the output stream. Both of these tasks can be facilitated by the use of a FIFO (First-In, First-Out) structure, through which the data flows.

Abstract: In a network including a first local area ATM network, a second local area ATM network and a public ATM network connected to the first and second ATM local area networks, multiplex gateway devices are interposed between the local area ATM networks and the public ATM network, respectively. The multiplex gateway apparatus includes ATM transmission line units for calculating statistical information represented by a mean rate and a peak cell rate of ATM cells in the transmission ATM signal. A statistical multiplexing control unit conducts rate addition after statistical multiplexing according to the statistical information and determines the rate addition result. A piece-wise constant bit rate control unit calculates a required piece-wise constant bit rate on the basis of the rate addition result and performs cell multiplex control on the basis of this piece-wise constant bit rate.

Abstract: A packet processing system converts a wide bus carrying P packets to a narrower bus that can carry only Q packets, where Q<P. The packet processing system includes a first data path, a queue, a shift register and a control unit. The first data path receives up to P packets during a first processing cycle. The queue stores the P packets in a queue. The control unit shifts a first quantity of data of the P packets into the shift register from the queue and selectively retrieves data from the shift register until a first packet of the plurality of packets is retrieved. The control unit then sends the first packet on a second data path during the first processing cycle.

Abstract: A switching device in a network system for transferring data includes one or more source line cards, one or more destination line cards and a switching fabric coupled to the source line cards and the destination line cards to enable data communication between any source line card and destination line card. Each source line card includes a request generator to generate a request signal to be transmitted in order to obtain an authorization to transmit data. Each destination line card includes a grant generator to generate and send back a grant signal to the source line card in response to the request signal received at the destination line card to authorize the source line card to transmit a data cell to the destination line card.

Abstract: The invention provides an arbitration method and an arbiter circuit by which equal arbitration of output cells can be achieved with a comparatively simple configuration even where a very great number of queues are involved. The arbiter circuit includes a plurality of queues for storing output cells, and a plurality of round robins for successively providing the right of outputting output cells to the queues. The round robins are arranged in a multi-stage tree link configuration, and the queues are distributed under those of the round robins which are in the lowest order stage. Each of the round robins in the lowest order stage has a rate information holding function of holding rate information representative of a rate of cells inputted thereto.

Abstract: Upon receipt of a synchronization request from the CPU, the AAL1 device of the act system causes its cell forming section to extract the allocation position information for the SAR-PDU payload about a particular time slot in the current frame and, via the synchronization information send/receive section, transfers the information to the AAL1 device of the standby system. The AAL1 device of the standby system causes its operation processing section to calculate the allocation position of a particular time slot in the next frame for the SAR-PDU payload based on the above allocation position information. The AAL1 device of the standby system starts allocation of the data of and following a particular time slot of the next frame to the SAR-PDU payload starting from the position indicated by the calculation result.

Abstract: A transmitting system inserts runt abort packets in an outgoing data stream during idle time inter-frame time fill. The runt abort packets cause the receiving system to synchronize itself to the transmitting system so that even if an error during inter-frame time fill causes the receiving system to go into an erroneous state, the receiving system will be synchronized with the transmitting system before receiving valid data. In one embodiment, the transmitting system transmits data in packets over SONET. The packet data is scrambled at the transmitting end and descrambled at the receiving end. Runt abort packets sent during inter-frame time fill resynchronize the descrambler. If there is an error in the inter-frame time fill bytes, causing the receiving end descrambler to no longer be synchronized with the transmitting end scrambler, the runt abort packets will cause the descrambler to resynchronize state with the transmitting scrambler.

Abstract: A Cable Modem Termination System (CMTS) is partitioned into Line Cards, I/O Cards, and a midplane to provide enhanced Reliability, Availability, and Serviceability. Each I/O Card provides a cabling interface for coupling an assigned Line Card to other portions of a Hybrid-Fiber-Coax Network. A plurality of RF signals is coupled via connectors between each Line Card and a corresponding I/O Card, via the midplane. This permits a Line Card to be removed for servicing without requiring recabling of the corresponding I/O Card. Preferably, a rectangular-multi-pin collinear connector-cascade (Line Card jack, midplane double-plug, and I/O Card jack) is used to couple the plurality of RF signals. The connector-cascade is configured with protective RF ground pins adjacent and surrounding each of a plurality of RF signal pins.