Abstract: A computing system (500) is configured to detect a Transmission Control Protocol (TCP) session hijacking attack on a TCP session. In particular, the computing system monitors for nonsequential packets of the TCP session. The nonsequential packets each comprise a sequence number (220) that is different from a next expected sequence number of the TCP session. The computing system (500) calculates, for each of a plurality of time intervals, a variation metric representing an extent to which the sequence numbers (220) of the nonsequential packets received in the time interval differ from the next expected sequence number. The computing system determines a variation baseline representing a trend of the variation metrics over time, and detects the TCP session hijacking attack on the TCP session based on the variation metric in a given time interval being different from the variation baseline by less than a threshold.

Abstract: A method (600) for operating a constrained device is disclosed, the constrained device being operable to communicate with an entity over a network. The method, performed by the constrained device, comprises generating a message for transmission to the entity (602), encrypting the generated message by applying a Pseudo Random Binary Sequence (PRBS) to the generated message (604), and transmitting the encrypted message to the entity (606). Also disclosed is a method (700) for operating an entity comprising receiving an encrypted message from a constrained device (702) and decrypting the encrypted message by applying a PRBS to the encrypted message. In some examples of the present disclosure, a constrained device and entity may dynamically renew the PRBS used for encryption and decryption of exchanged messages.

Abstract: A boundary node for interworking between a first network and a second network comprises first equipment for interfacing with the first network and second equipment for interfacing with the second network. The first equipment comprises a switch fabric. A first interworking interface and a second interworking interface are provided for carrying traffic between the second equipment and the first equipment. Each of the interworking interfaces is for interfacing with a respective traffic-carrying path of the second network. For traffic flow in a direction from the second network to the first network, a method comprises determining that recovery switching is required for traffic on one of the traffic-carrying paths of the second network and performs a recovery switch, using the switch fabric in the first equipment, to switch between the interworking interfaces to achieve a recovery switch between the traffic-carrying paths of the second network.

Abstract: A method distributes clock synchronization information within an optical communications network that includes a plurality of network elements. The method receives an ingress clock synchronization message at a first network element. The ingress clock synchronization message includes a clock synchronization message identifier and a correction field. The clock synchronization message identifier is inserted into an optical channel frame overhead and the ingress clock synchronization message is inserted into an optical channel frame payload. The optical channel frame overhead and the optical channel frame payload are transmitted across the first network element, across the network to a second network element, and across the second network element. A transit time of the clock synchronization message identifier is determined across each of the network elements.

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: A method distributes clock synchronization information within an optical communications network comprising a plurality of network elements. The method receives an ingress clock synchronization message at a first said network element. The ingress clock synchronization message includes a clock synchronization message identifier and a correction field. The clock synchronization message identifier is inserted into an optical channel frame overhead and the ingress clock synchronization message is inserted into an optical channel frame payload. The optical channel frame overhead and the optical channel frame payload are transmitted across the first network element, across the network to a second said network element, and across the second network element. A transit time of the clock synchronization message identifier is determined across each of the network elements.

Abstract: A method distributes clock synchronization information within an optical communications network having a plurality of network elements. The method receives an ingress clock synchronization message at a first network element. The ingress clock synchronization message includes a clock synchronization message identifier and a correction field. The clock synchronization message identifier is inserted into an optical channel frame overhead and the ingress clock synchronization message is inserted into an optical channel frame payload. The optical channel frame overhead and the optical channel frame payload are transmitted across the first network element, across the network to a second network element, and across the second network element. A transit time of the clock synchronization message identifier is determined across each of the network elements.

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 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 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: 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: A boundary node for interworking between a first network and a second network comprises first equipment for interfacing with the first network and second equipment for interfacing with the second network. The first equipment comprises a switch fabric. A first interworking interface and a second interworking interface are provided for carrying traffic between the second equipment and the first equipment. Each of the interworking interfaces is for interfacing with a respective traffic-carrying path of the second network. For traffic flow in a direction from the second network to the first network, a method comprises determining that recovery switching is required for traffic on one of the traffic-carrying paths of the second network and performs a recovery switch, using the switch fabric in the first equipment, to switch between the interworking interfaces to achieve a recovery switch between the traffic-carrying paths of the second network.

Abstract: A method distributes clock synchronization information within an optical communications network having a plurality of network elements. The method receives an ingress clock synchronization message at a first said network element. The ingress clock synchronization message includes a clock synchronisation message identifier and a correction field. The clock synchronisation message identifier is inserted into an optical channel frame overhead and the ingress clock synchronisation message is inserted into an optical channel frame payload. The optical channel frame overhead and the optical channel frame payload are transmitted across the first network element, across the network to a second said network element, and across the second network element. A transit time of the clock synchronisation message identifier is determined across each of the network elements.

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: 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: 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: Network node comprising input equipment, switching equipment and output equipment, the input equipment is arranged to be capable of packetizing time division multiplexed (TDM) traffic flows, the switching equipment is arranged to be capable of routing the packetized 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 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 synchronization message identifier and a correction field. The first network element inserts the clock synchronization message identifier into an optical channel frame overhead and inserts the ingress clock synchronization 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 synchronization message identifier across each of the network elements. The second network element updates the correction field of the ingress clock synchronization message with said transit times to form an egress clock synchronization message.

Abstract: An optical transport network comprises a first node and a second node adapted to communicate one or more lower order optical channel data unit (LO-ODU) traffic signals via a higher order optical channel data unit (HO-ODU) traffic signal. An adaptation function between a lower order optical channel data unit traffic signal and a higher order optical channel data unit traffic signal is modified to enable protocol information for bidirectional protection switching to be conveyed in one or more lower order optical channel data unit traffic signals that are conveyed between the first node and the second node using the higher order optical channel data unit traffic signal. This enables the protocol information to be used at a higher order optical channel data unit entity to perform bidirectional protection switching.

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.