Abstract: A failure protection between interconnected adjacent Resilient Packet Rings (RPRs) in a multiple RPR network is provided. Two paths, a regular message path and a protection path, are provided between two adjacent RPRs. The regular path is used for routing inter-ring messages when no failure has occurred on the path. Messages are rerouted through the protection path when a failure occurs on the regular path. Each of these paths has two RPR interface nodes (one for each RPR) that are connected to an interconnection device (a layer 2 bridge or a layer-3 router) through interconnection links. Procedures for detecting failures and generating notifications for message rerouting and fault reports are executed at the interconnection devices. The procedures use periodic keep alive messages for diagnosing network segment and interconnection device failures. The fault detection and message rerouting are accomplished in less than 50 ms.

Abstract: Cascaded policing methods and systems are provided which allow lower priority traffic to benefit from otherwise unused capacity allocated to higher priority traffic of a given customer/service with multiple classes of service. The method involves policing packets of a first class in accordance with at least one policing parameter associated with the first class, and policing packets of a second class in accordance with at least one policing parameter associated with the second class in a manner which gives to the second class at least a portion of a traffic throughput afforded to the first class by at least one of said at least one policing parameter, such as a rate guarantee or burst tolerance, associated with the first class of traffic which is not being used by the packets of the first class. The method is easily adapted to an arbitrary number of different traffic classes.

Abstract: A method and system for providing protection of data communications in packet-based networks is provided, using a combination of unicast to multicast conversion and providing formation of virtual output queues (VOQs) which are separate for each pair of the target port and protection ports on the target network device. As a result, the system requires less bandwidth resources and reduces or eliminates network performance problems associated with other existing solutions.

Abstract: A method and system for identification of a channel in an optical network is provided. The channel is identified by the use of unique combinations of two or more low frequencies, or tones, modulated onto the channel and optionally, a network parameter associated with the channel.

Abstract: The invention provides a method and system for fast scheduling using a work-conserving Round Robin strategy. The method and system select one of a plurality of queues of data packets for switching it to an output port in a current timeslot, for achieving work-conserving Round Robin scheduling. The method is based on a consideration range for each queue that is a set of queues having priority over the given queue. The method comprises the steps of generating a mask for a given queue for masking all queues outside a consideration range of the given queue and applying the mask and a queue ready flag for the given queue for determining if the given queue is to be selected in the current time slot.

Abstract: The invention provides a method and system for selectively canceling a specified frequency band in the payload of an optical communication system. This selected frequency band is to be used for launching pilot tones for power measurement and identification. The method controls the intensity of the optical payload signal through an intensity modulator that is included in the optical communication system. The frequency band in payload to be cancelled is removed where as the other frequency components of the payload are passed without attenuation. An embodiment that uses a feed-forward unit, a feedback unit and a control unit for generating a cancellation signal for the intensity modulator is described. An advantage of the method is that it removes a continuum of payload tones in the specified frequency band to be cancelled.

Abstract: A routing system and method are provided which use a composite cost in identifying routes. This allows a simple way of identifying the best route taking multiple metrics into account for each link simultaneously. The system allows for the inclusion of pruning constraints, and allows for various objectives such as bin packing or load balancing to be achieved.

Abstract: The invention describes methods and systems for monitoring the performance of an optical network by marking a group of optical signals with a set of identification tags which are unique to network characteristics. In the preferred embodiments, fiber identification (FID) and bundle identification (BID) tags are encoded into optical signals by marking an optical signal with low frequency dither tones whose frequencies are unique to the fiber section and to a bundle of fibers respectively. Detecting of the FID and BID tones provides more effective and accurate monitoring of performance of the optical network and allows determining of the network topology, e.g. paths of optical channels and traffic load through different fiber sections in the network. Other sets of hierarchically arranged identifiers encoded into optical signals have also been proposed, including band, conduit, city, region, country, etc. identifiers, as well as identifiers related to network security and service characteristics.

Abstract: A multi-protocol label switching (MPLS) packet network, methods and traffic engineering extensions to label distribution protocol are provided, capable of carrying traffic of multiple classes of service over the same label switch path.

Abstract: A switch module for a communication network switch comprises first and second switching units each for communicating with one or more network communication interfaces, and a switch interface connected to each of the first and second switching units and having a pair of communication ports for enabling data to be transferred on to a local communication path which is connected between the local communication ports.

Abstract: Channels in an optical WDM network are each identified by at least two dither tones with which the channel is modulated, the dither tones alternating with a predetermined periodicity so that at any instant each channel is modulated by only one dither tone. The dither tones are continuously generated at precise frequencies. Channel detection by detecting the dither tones, for channels having optical powers over a wide dynamic range, makes use of an FFT process which can detect dither tones for high power channels in a single operation. Coherent averaging of FFT results over time is used to detect dither tones for low power channels over multiple FFT operations.

Abstract: Channels in an optical WDM network are each identified by at least two dither tones with which the channel is modulated, the dither tones alternating with a predetermined periodicity so that at any instant each channel is modulated by only one dither tone. The dither tones are continuously generated at precise frequencies. Channel detection by detecting the dither tones, for channels having optical powers over a wide dynamic range, makes use of an FFT process which can detect dither tones for high power channels in a single operation. Coherent averaging of FFT results over time is used to detect dither tones for low power channels over multiple FFT operations.

Abstract: A method and system for identification of a channel in an optical network is provided. The channel is identified by the use of unique combinations of two or more low frequencies, or tones, modulated onto the channel and optionally, a network parameter associated with the channel.

Abstract: A method and system for multi-level power management in an optical network is provided. They include three levels of power management. The first level of power management dynamically changes equipment settings in each module of equipment so that required module setpoint values in each module are achieved. The second level of power management determines module setpoint values for each module of equipment within each node in the optical link so that required node setpoint values are achieved. The third level of power management determines node setpoint values at each node in the optical link so that the optical link meets predetermined power specifications. If any of the three levels cannot achieve the required setpoint values, an error signal is generated by that level of power management and sent to the level of power management above it, thus initiating a higher level of power management.

Abstract: An optical add/drop multiplexing (OADM) apparatus and method are disclosed for detecting pilot tones, removing ghost tones, and re-inserting pilot tones on WDM signals in an optical network. The OADM apparatus comprises a smart processing and control unit (PCU) for detecting pilot tones used for channel identifications, including identifying and removing ghost tones associated with respective optical channels, and re-inserting the processed pilot tones into the respective optical channels. The OADM apparatus and method may incorporate digital PCU or analog PCU for processing pilot tones and removing ghost tones.

Abstract: A multi-stage method and apparatus for determining a faulty component location along an optical path through an optical fiber in an optical network are disclosed. A total power of the optical fiber, and a total wavelength power as a sum of powers of the individual wavelengths at a plurality of local detection points are measured and compared at the local detection points, followed by determining whether or not a faulty detection point exists along the optical path. If a fault is identified, the method provides a multi-stage fault detection procedure, including measuring a total wavelength power loss between a local detection point and an adjacent detection point, between the local detection point and multiple non-adjacent detection points, and a correlation of the measured total wavelength power losses between the various detection points. A corresponding apparatus for determining the faulty component location in the optical network is also provided.

Abstract: A high-speed packet memory is provided, the memory having a write port and a read port and comprised of the following: a plurality of N memory modules for storing fixed size cells, which are segments of a variable size packet divided into X cells, the X cells being grouped into [X/N] groups of cells; a read-write control block comprising a means for receiving cells from the write port and storing each cell, which belongs to the same group, in a selected different one of the N memory modules at the same memory address (the group address); a multi-cell pointer (MCP) storage for storing an MCP for said group of cells (an associated MCP) at an MCP address, the MCP having N memory module identifiers to record the order in which cells of said group of cells are stored in the N memory modules; and the MCP address being the same as the group address. Corresponding methods for storing cells and/or storing and retrieving variable size packet in such memory are also provided.

Abstract: A communication system such as a distributed packet switch, is described, including multiple nodes with bi-directional transmission links between the nodes, each link comprising of a set of multiple links in parallel. The system provides an automatic balancing the aggregate capacity of one set of links in a proportion “M:N” to the aggregate capacity of the other set of links under varying link conditions, including one or more individual link failures in one or both sets of links.

Abstract: A reliable packet network is constructed with nodes and links where the nodes use a method for fast distribution of link state information. This permits a rapid update of the routing information at all nodes in case of a link failure, minimizing the number of lost packets.

Abstract: A method and system for compensating for side effects of cross gain modulation in amplified optical networks, which allows reliable identification of expected and unexpected channels in the network is provided. Each optical channel traveling in the optical network is marked with a unique channel signature (expected channel signature), having one or more dither tone modulated onto the optical channel; followed by detecting a spectrum of tones, including said modulated dither tones and ghost tones thereof produced by the cross gain modulation in the optical network, at various locations in the optical network. Amplitudes of the spectrum tones, which belong to the expected channel signature, are compared with a first threshold, while amplitudes of the remaining spectrum tones, which are not the valid tones, are compared with a second threshold, which is lower than the first threshold.