Abstract: An optical network unit having an environmentally sealed printed circuit board arrangement within a first compartment and a signal in/out arrangement in a second compartment. The compartments are provided by two housings. Instead of replacing individual circuit boards in the case of breakdown or malfunction, replacement of the whole of the printed circuit board arrangement is necessary thereby eliminating human error and minimizing downtime. Two housings provide the two compartments. These housings are preferably mounted upon a housing mount and a carrier for the optical network unit is also preferably mounted upon the housing mount. This housing and carrier arrangement simplifies assembly and disassembly of parts of the unit for maintenance and replacement purposes.

Abstract: The present invention comprises a method and apparatus for automatic discovery of logical links between network devices. In one embodiment, the present invention comprises part of a network management system (“NM”) that manages a discrete set of network devices. The NM sends SNMP queries to individual network devices managed by the NM to obtain interface configuration data for each of the network interfaces of the device. The information requested includes destination information (“next hop” or “neighbor” IP address) for data packets sent from the interface. The NM checks to see whether a logical link corresponding to the received configuration information already exists in a logical link database maintained by the NM. If such a link exists the NM checks to see if the existing information for the link is valid. If the existing link data is valid, no change is made.

Abstract: The present invention comprises a method and apparatus for automatic discovery of network devices with data forwarding capabilities. In one embodiment, the present invention sends SNMP queries to sets and/or ranges of IP numbers to determine whether a network device exists at each IP number and whether the network device has IP forwarding capabilities. The set of IP numbers searched may be specified by specifying ranges or subnets or by providing a list of discrete IP numbers. When a new network device with IP forwarding capabilities is discovered, that network device (identified by its IP number and SNMP description field) is added to a list of discovered network devices. The list is displayed to the network manager, who has the option of selecting none, one, or more than one of the network devices on the network device list for management by the network manager's network management system.

Abstract: A bridged virtual LAN (VLAN) has a number of segments connected by a connection-based network such as an ATM network. Multicast data originating in a first one of the segments is carried to two or more other segments by a point-to-multipoint virtual channel configured in the connection-based network. A separate point-to-point virtual channel may be provided for other data and bidirectional control signals. The segments may be ethernet segments with data flow over the point-to-multipoint virtual channel being unidirectional. Ethernet frames may be carried by a protocol such as AAL5.

Abstract: A modulation system having in-phase and quadrature phase (IQ) calibration while on-line. The modulation system includes an on-line correction data state detector, an IQ correction code, and a scalar amplitude detector. The on-line correction state detector detects the presence of particular data states that are expected to result in particular modulation states or transition locations. When a particular data state is detected the IQ correction code compares the detected scalar magnitude with others that have been detected. The IQ correction code then uses the comparison to generate adjustments for I and Q offsets, I/Q phase, and I/Q gain. In a rotation embodiment, the modulation system further includes a rotation signal generator for generating rotation angles and an IQ rotator for applying the rotation angles for rotating the I and Q digital data streams.

Abstract: A method and apparatus for data flow control of a transmission port includes processing that begins by obtaining, for the transmission port over time, input data rate of at least one data transport type and output data rate of the at least one data transport type. The data type transport type is one of available bit rate (ABR), variable bit rate (VBR), constant bit rate (CBR), and unspecified bit rate (UBR). The data flow control continues by deriving a difference term from the input data rate and the output data rate and using the difference term and a previous generic explicit rate to generate a current generic explicit rate. The current generic explicit rate may further be generated from the previous generic explicit rate, the difference term, and an error term, where the error term is derived from a current queue value and a target queue value.

Abstract: A method and apparatus for converting UBR and nrt-VBR connections to ABR connections in an ATM network is presented. In response to receiving a connection set-up message for a UBR or nrt-VBR connection, it is determined it is determined whether the port contemplating conversion is commissioned as a conversion port, which enables it to perform such conversions. If the port is a conversion port, it is determined whether or not the port type of the ingress port and the port type of the egress port support connection format conversion. If the port types support connection format conversion, it is determined whether or not the set-up message for the connection indicates that the connection is conversion enabled. If the connection is conversion enabled and the ports are of the right configuration, the set-up message is converted from the nrt-VBR or UBR format to an ABR format for transmission.

Abstract: A method is disclosed for establishing a switched virtual circuit in a digital network having network nodes with static routing tables. The static routing tables contain at least primary and alternate routing data. When a node is unable to forward a call over its outgoing primary route due to congestion or physical failure and its alternate route is the same as the route on which a call setup request arrived, it clears the call at that node and sends a crankback message to the preceding node, which responds to the crankback message to attempt to dynamically re-route the call over the alternate route stored in the routing table of the preceding node. If the attempt is unsuccessful, it sends the message back to the next preceding node and so on.

Abstract: A combination of a security cabinet and electronic equipment housed with the security cabinet in which cooling air is passed directly from outside the cabinet into the equipment so as to bypass air within a chamber of the cabinet. Preferably, a conduit is provided which extends between a wall of the cabinet to the equipment to introduce the cooling air from ambient atmosphere into the equipment. A method is also provided for introducing cooling air directly from outside the cabinet into the equipment. The method and combination enable lower operating temperatures of electronic equipment to be maintained than is possible with existing equipment housed in security cabinets.

Abstract: Fixed access wireless networks generally includes a grouping of cells, with each cell comprising a base transceiver station in radio frequency contact with a plurality of terminal stations. Such networks are typically assigned a limited number of frequencies to facilitate data transfer. Various techniques are used to maximize the amount of data which can be transferred including polarization, modulation and frequency reuse. A Local Multi-point Distribution System (LMDS) is a form of fixed wireless network, a notable feature of which are the directional nature of their terminal station antennae. The present invention provides a method of assigning frequencies to an LMDS, by exploiting the directivity of the fixed terminal station antennae. Each cell is divided into an even number of at least four sectors. Given a desired carrier to interference ratio, the cells are grouped into clusters, the cluster size defining the interference boundary for a given cell in the cluster.

Abstract: A system and method for calculating round trip delay (RTD) values in a switched digital network such as an asynchronous transfer mode (ATM) network. A loopback cell such as an ATM operation and maintenance (OAM) cell is used to carry a delta value through the network. The delta value, which represents a processing interval at a loopback node or an intermediate node, is calculated utilizing timestamps generated at specific ingress and egress ports of network nodes. Cell Transfer Delay (CTD) and Cell Delay Variations (CDV) values are calculated based on the measured RTD.

Abstract: In a connection oriented communications network such as an asynchronous transfer mode (ATM) network, virtual circuit (VC) connections are aggregated onto virtual path (VP) connections to simplify traffic management through core switching elements. This invention provides a system and a method of introducing network level fairness between VP connections in the core. Resource management (RM) cells are used to import relevant traffic weighting parameters from the VC/VP aggregation point to the VP switching element. The weighting parameters are used by a queuing scheme at each switching function to introduce a fairness level component to each VP.

Abstract: A housing for electronic equipment having a cooling air flow passage system of first and second parts. The first part receives incoming cooling air, the air flowing through the first part and then, at one location, flowing from the first part into and then along the second part of the system. At a second location, some of the cooling air is returned into the first part of the system, the remainder of the cooling air having been expelled from the housing. Because of the return of cooling air into the first part of the system, there is an accumulation of incoming and returned air to pass along the first part of the system and this accumulation is greater than the rate at which air is entering and is being expelled from the housing. As a result, the accumulation of air travels at an extremely high flow rate through the first part of the system so as to maximize the removal of heat from electronic components.

Abstract: A method of minimizing throughput delay in constant-bit-rate services carried over packet-based networks subject to variable delays, comprises, in one embodiment, the steps of receiving incoming packets in a buffer, reading out bits from the buffer at a clock frequency fi, continually monitoring the buffer fill level Li, determining the maximum fill level Lmaxj over a plurality of successive samples, determining the minimum fill level Lmink over a plurality of successive samples, adjusting the clock frequency fi to cause the maximum fill level Lmaxj to tend toward a target value TargetLmax, and adaptively changing said target value TargetLmax so that the minimum fill level Lmink tends toward a predetermined set-point. The rate of change of the target value TargetLmax is significantly slower than the rate of adjustment of clock frequency. The invention can be applied to other types of clock recovery.

Abstract: A method and apparatus is for buffering data cells in a queuing element is presented. Each queuing element includes a partitioned buffer, where the partitioned buffer includes a plurality of partitions. Each of the partitions stores data cells received by the queuing element. Storage of the data cells into the partitions is accomplished by using an array of logical queues. Each logical queue of the array of logical queues maps data cells corresponding to that logical queue to a particular partition of the plurality of partitions. More than one logical queue may map data cells to a particular partition. Each partition may include a reserved portion, where each logical queue that maps to the partition may map a portion of its data cells to the reserved portion. The resources of the reserved portion to which a logical queue maps data cells are reserved to that specific logical queue and cannot be utilized by other logical queues.

Abstract: In source routed or hop-by-hop routed protocol communication networks, when congestion is detected at a certain network element, a notification message is sent to nodes. The nodes keep track of congestion condition and generally have knowledge of the congestion, thereby allowing them to make more intelligent routing decisions, i.e., rate controlling messages, routing traffic around congestion, regulating admission at the edge of the network. The intelligent routing decision is based on the congestion condition indicated by a restriction level which is periodically and dynamically updated.

Abstract: A shaping algorithm for use in a queuing system in which there is no background process for detecting clock wrap around. The algorithm applies to Asynchronous Transfer Mode (ATM) applications and to the different categories of service connections specified by the ATM Forum. The algorithm is implemented by a time slotted calendar system to shape cell streams into conformance with network traffic descriptors. The calendar register is constrained to positive values to ensure valid results from the maximum functions carried out by the Algorithm. The register is divided into quadrants and the location of theoretical cell emission times relative to current and next time slots within the quadrants is used to detect clock wrap around.

Abstract: A method and system for providing routing information for use in virtual private networks is disclosed. The method supports a variety of different secure network topologies. According to the method a static map is generated including information on each static gateway and resources accessible therethrough. The map also contains security information for accessing and authenticating a gateway.

Abstract: A high speed programmable ER computational engine that is based on a micro-programmed control unit and a register intensive pipelined datapath that removes the need for having an instruction set interpreter includes a data path unit operably coupled to directly receive datapath control words from a control unit. The control unit includes memory and an address unit, where the memory stores the data path control words, which relate to a computational algorithm. The address unit receives input (e.g., begin an ER calculation) from an external source, where the input causes at least some of the data path control words to be retrieved from the memory. The data path unit includes a pair of register files, a plurality of floating point units, and data flow coupling. The pair of register files operate in a double buffering manner such that one of the register files is receiving parameters (e.g., data rate information of a connection) for subsequent computation while the other is used for a current computation.

Abstract: There is provided a method and device for measuring a rate of message element traffic over a message path in a communications network. The path includes at least one connection and is associated with a maximum rate of transmission. The path is periodically polled for transmission of a message element, the polling being performed at a polling rate associated with polling intervals which are at least as frequent as the maximum rate of transmission. If transmission of a message element is detected during a polling interval, a running count of such detection is incremented, the running count of detection being associated with the connection over which the message element was detected. If transmission of a message element is not detected, a running count of such non-detection is incremented, the running count of non-detection being associated with inactivity of the message path.