Abstract: The invention relates to a protection mechanism for a communications network. A node, a method, a computer program product and a communications network to provide protection for an optical communications network are disclosed. Communications traffic is selecting from a working path in the optical network. A first fault condition is determining on the working path. The communications traffic is selected from a protection path in the optical network in response to clearing of the first fault and determining a second fault condition on the working path within a first predetermined time period of determining the first fault condition.

Abstract: A method for adapting the rates of a certain number of asynchronous HDLC channels (15) to a single clock domain suited for interfacing with an HDLC processor (13) through a synchronous pseudo-TDM interface (14) in which the HDLC channels are multiplexed in time and vice versa in the opposite direction. In one direction the algorithm is based on the writing of the HDLC channels in a dedicated buffer (17) and in reading these buffers with a common synchronous clock just above the expected maximum HDLC rate. The under-run condition is avoided by inserting neutral information between the end byte and the start byte of the HDLC packets when this is suggested by the buffer fill monitoring function. A simple function to locate the first and last bytes of each HDLC packet read by the buffer is hence used in combination with the buffer fill monitoring function.

Abstract: A node for a communications network has a converter for digitizing at a receiver clock rate a received optical signal received over an optical link from an optical transmitter at a source node, a framer for detecting frames and a forward error correction part for correcting errors in the payload of the frame. An error rate in the received payload part is monitored and a processor sends, according to the monitored error rate, a request to the optical transmitter to adapt a length of the transmitted forward error correction part and to adapt a clock rate of the transmission of the frame if FEC length is reduced or FEC is disabled. This can enable power saving, when less FEC information is being sent.

Abstract: A method and system of distributing clock synchronization information within an optical communications network including a plurality of network elements, in which a first network element receives an ingress clock synchronization message, the ingress clock synchronization message including a clock synchronisation message identifier and a correction field. The first network element inserts the clock synchronisation message identifier into an optical channel frame overhead and inserts the ingress clock synchronisation message into an optical channel frame payload. The first network element transmits the optical channel frame overhead and the optical channel frame payload to a second network element, and determines a transit time of the clock synchronisation message identifier across each of the network elements. The second network element updates the correction field of the ingress clock synchronisation message with said transit times to form an egress clock synchronisation message.

Abstract: The invention relates to data networks, and in particular relates to a method and apparatus for forming and processing data units to enable the transfer of clock quality information in data networks. A method of forming a higher order data unit, comprising payload data and overhead data, from a plurality of lower order data units, is disclosed. The payload of the higher order data unit is formed by combining the plurality of lower order data units. The overhead data of the higher order data unit includes clock quality information relating to clocks associated with the plurality of lower order data units. Embodiments provide a way of transporting clock quality information relating to clocks associated with a number of lower order data units within a single higher order data unit, and enables intermediate networks easily to access the clock quality information.

Abstract: Configuring a node (410) of a synchronization network involves identifying (10) possible alternative time synchronization trails arranged to carry time synchronization information for time synchronization at the node, and possible alternative frequency trails, arranged to carry frequency synchronization information for frequency synchronization at the node. Using information about the sources (20), a comparison of the trails (30) is biased to increase a likelihood of choosing time synchronization and frequency trails which share the same source, over a likelihood of choosing trails with different sources. This can help avoid divergence and consequent bit errors arising from phase errors, resulting from trails having different sources. It can encompass for example changing both to a new common source, or changing one or both trails while still using the old common source.

Abstract: There is provided a method of optimizing timing packet transport in a network node, the method comprising using a locally available stable frequency reference at the network node to provide a pre-determined network node transit time for timing packets in at least one direction into or out of the network node. There is also provided a network node comprising a locally available stable frequency reference and circuitry adapted to apply a pre-determined network node transit time, L, to all timing packets transiting the network node in at least one direction into or out of a network node dependent on the locally available stable frequency reference.

Abstract: An optical transport network signal (OTM) comprising at least one optical channel is received at a first network equipment. The optical transport network signal (OTM) is processed to extract optical data units (ODUk) for each optical channel (OCh). There is detection for defects during the processing. The optical data units are retransmitted within optical transport units (OTUk) towards a second network equipment. When a defect has been detected, the retransmitting comprises inserting an optical channel transport unit alarm indication signal (OTUk-AIS) in an optical channel transport unit (OTUk) containing optical channel data units (ODUk) that are affected by the detected defect.

Abstract: A method of clock recovery of Time Division Multiplex signal in a packet network, wherein a first Provider Edge receives a timing message from a second Provider Edge and upon reception of said timing message a counter of said first Provider Edge is increased. The first Provider Edge sends to the second Provider Edge encapsulated Time Division Multiplex packet traffic and each packet sent to the second Provider Edge causes the counter to decrease. The first Provider Edge compares value of the counter with an Upper Threshold value and with a Low Threshold value and increases a rate of generation of the encapsulation packets if the counter is above said Upper Threshold or reduces the rate of generation of the encapsulation packets if the counter is below said Low Threshold.

Abstract: A method of routing data through a router in a communications network, the method comprising receiving one or more data packets, each packet having a respective destination address and applying a lookup algorithm to each packet, said lookup algorithm being arranged to determine a respective route along which each packet is to be transmitted towards its destination address by searching an associated hierarchical data structure containing routing information for each packet. The method comprising forwarding each packet for transmission to its respective destination address, wherein said lookup algorithm comprises an adaptive learning component that is configured to dynamically identify an optimum starting position for searching within said hierarchical data structure, for each of the data packets, based on the results of one or more earlier searches.

Abstract: The invention relates to a protection mechanism for a communications network. A node, a method, a computer program product and a communications network to provide protection for an optical communications network are disclosed. Communications traffic is selecting from a working path in the optical network. A first fault condition is determining on the working path. The communications traffic is selected from a protection path in the optical network in response to clearing of the first fault and determining a second fault condition on the working path within a first predetermined time period of determining the first fault condition.

Abstract: A method for protection of STM-n/OC-n clear channel connections calls for a protection diagram allowing protection of STM-n/OC-n clear channel signals transmitted from a source point to a destination point. This protection allows overcoming a fall along the path between source point and destination point. It can be used in different types of network structure, for example “ring” or “mesh”. The method calls for duplication of STM-n/OC-n signals at the transmitting end of the subnetwork and transmission over two different routes which can be defined as work and protection paths. To ensure success of the protection diagram the work and protection channels follow different routes. At the receiving end, the signal is selected from the work path or the protection path depending on the quality of the received signals, the protection state and the external commands.

Abstract: Network node comprising input equipment, switching equipment and output equipment, the input equipment is arranged to be capable of packetising time division multiplexed (TDM) traffic flows, the switching equipment is arranged to be capable of routing the packetised data from the input equipment to the output equipment, and the output equipment is arranged to be capable of reassembling the flows into time division multiplexed format, wherein the input equipment is also arranged to be capable of causing the data frequency of the packetized data sent to the switching equipment to be substantially equal to a predetermined data frequency.

Abstract: A method for adapting the rates of a certain number of asynchronous HDLC channels (15) to a single clock domain suited for interfacing with an HDLC processor (13) through a synchronous pseudo-TDM interface (14) in which the HDLC channels are multiplexed in time and vice versa in the opposite direction. In one direction the algorithm is based on the writing of the HDLC channels in a dedicated buffer (17) and in reading these buffers with a common synchronous clock just above the expected maximum HDLC rate. The under-run condition is avoided by inserting neutral information between the end byte and the start byte of the HDLC packets when this is suggested by the buffer fill monitoring function. A simple function to locate the first and last bytes of each HDLC packet read by the buffer is hence used in combination with the buffer fill monitoring function.

Abstract: A method for adapting the rates of a certain number of asynchronous HDLC channels (15) to a single clock domain suited for interfacing with an HDLC processor (13) through a synchronous pseudo-TDM interface (14) in which the HDLC channels are multiplexed in time and vice versa in the opposite direction. In one direction the algorithm is based on the writing of the HDLC channels in a dedicated buffer (17) and in reading these buffers with a common synchronous clock just above the expected maximum HDLC rate. The under-run condition is avoided by inserting neutral information between the end byte and the start byte of the HDLC packets when this is suggested by the buffer fill monitoring function. A simple function to locate the first and last bytes of each HDLC packet read by the buffer is hence used in combination with the buffer fill monitoring function.

Abstract: A method of clock recovery of Time Division Multiplex signal in a packet network, wherein a first Provider Edge receives a timing message from a second Provider Edge and upon reception of said timing message a counter of said first Provider Edge is increased. The first Provider Edge sends to the second Provider Edge encapsulated Time Division Multiplex packet traffic and each packet sent to the second Provider Edge causes the counter to decrease. The first Provider Edge compares value of the counter with an Upper Threshold value and with a Low Threshold value and increases a rate of generation of the encapsulation packets if the counter is above said Upper Threshold or reduces the rate of generation of the encapsulation packets if the counter is below said Low Threshold.

Abstract: The present invention consists of an information structure conceived for the transport of data in digital form from a transmitting element to a receiver. This structure calls for fields for transport of the data and heading information fields termed “overhead” which improve transmission reliability. This structure enables support of digital interconnections in an element of a transport network capable of switching various traffic types such as CBRx (for example STM-N e OC-N), VC-N, STS-N or ODUk. The structure also enables identification of the frame beginning, verification of the integrity and correctness of the switching, support of protection switching, and transport of quality and timing information associated with the switched entities.

Abstract: A method for generation of a clock synchronized with time reference signals derived from input signals in an apparatus of a telecommunications network comprising an input part receiving the input signals and a treatment part for treatment of the input signals. In the input part the method comprises the steps of deriving the time reference signals from the input signals, reading an edge of the reference signals, establishing the position of this edge relative to the internal data frame, inserting in the frame heading a pointer representing the established position of the edge relative to the frame and sending the frame to the treatment part. In the treatment part the method comprises the steps of receiving the frame, extracting the pointer, generating the time reference clock and synchronizing it with the position in the frame indicated by the pointer. An apparatus applying this method is also proposed.

Abstract: A method for adapting the rates of a certain number of asynchronous HDLC channels (15) to a single clock domain suited for interfacing with an HDLC processor (13) through a synchronous pseudo-TDM interface (14) in which the HDLC channels are multiplexed in time and vice versa in the opposite direction. In one direction the algorithm is based on the writing of the HDLC channels in a dedicated buffer (17) and in reading these buffers with a common synchronous clock just above the expected maximum HDLC rate. The under-run condition is avoided by inserting neutral information between the end byte and the start byte of the HDLC packets when this is suggested by the buffer fill monitoring function. A simple function to locate the first and last bytes of each HDLC packet read by the buffer is hence used in combination with the buffer fill monitoring function.

Abstract: The present invention consists of an information structure conceived for the transport of data in digital form from a transmitting element to a receiver. This structure calls for fields for transport of the data and heading information fields termed “overhead” which improve transmission reliability. This structure enables support of digital interconnections in an element of a transport network capable of switching various traffic types such as CBRx (for example STM-N e OC-N), VC-N, STS-N or ODUk. The structure also enables identification of the frame beginning, verification of the integrity and correctness of the switching, support of protection switching, and transport of quality and timing information associated with the switched entities.