Abstract: A synchronization system node may comprise one or more processors and a synchronization database. The synchronization database may comprise a subscriber list of a plurality of subscribers, a first buffer including a plurality of attributes in a first state, and a second buffer including the plurality of attributes in a second state. The node may be configured to receive updates for one or more of the plurality of attributes and store, to the first buffer, the updates for the one or more of the plurality of attributes to update the plurality of attributes of the first buffer to an updated first state. While receiving the updates from the publisher, the nod may publish, from the second buffer to a first subscriber of the plurality of subscribers, one or more of the plurality of attributes in the second state.

Abstract: A system and method for managing a system topology of a distributed computing system comprising: providing a network of clusters with at least a first cluster and a second cluster; configuring the first cluster with an external gateway configuration of the second cluster; distributing the external gateway configuration across at least a subset of nodes of the first cluster; establishing a connection between all clusters from the network of clusters, which for the first and second cluster comprises: for each node of the first cluster, establishing a single outbound connection to a select node of the second cluster; and managing communication over the system topology comprising: at a receiver node of the second cluster, propagating a subscription interest, and at an origin node of the first cluster, transmitting communications over the connection according to the subscription interest.

Abstract: A communication device in a communication network includes at least one processor. The at least one processor is configured to at least one processor configured to search a spectrum of the communication network using a Long Term Evolution Primary Synchronization/Secondary Synchronization Signals (LTE PSS/SSS), estimate the LTE interference using cell specific reference signals for Down Link (DL) when the LTE PSS/SSS signal is detected, and utilize LTE cell specific reference signals (CRS) and feed the equalized signal to a Data Over Cable Service Interface Specification (DOCSIS) Physical Layer (PHY) engine.

Abstract: A system for controlling accesses to network enabled devices includes a network interface over which a hub communicates with network enabled devices, a processor, and a multilayer access control layer. The access control layer includes instructions that, when executed by the processor, cause the processor to detect, at the hub, a request representing an attempt by an application executing on a remote host device to access a network enabled device communicatively coupled to the hub, characterize the request according to a user of the remote host device, the application making the attempt, and the network enabled device, and determine whether to allow or deny the request based upon the characterization and a plurality of rules. The rules may include definitions of access rights, with respect to the network enabled device, for users, applications, commands or queries made by applications, remote host devices, and network domains.

Abstract: A system and method for managing a system topology of a distributed computing system comprising: providing a network of clusters with at least a first cluster and a second cluster; configuring the first cluster with an external gateway configuration of the second cluster; distributing the external gateway configuration across at least a subset of nodes of the first cluster; establishing a connection between all clusters from the network of clusters, which for the first and second cluster comprises: for each node of the first cluster, establishing a single outbound connection to a select node of the second cluster; and managing communication over the system topology comprising: at a receiver node of the second cluster, propagating a subscription interest, and at an origin node of the first cluster, transmitting communications over the connection according to the subscription interest.

Abstract: A tool listening device including a transceiver is configured to listen on a radio channel selected from a discovery channel hopping sequence. The tool listening device is configured to identify a preamble, indicating a start of a packet. The tool listening device continues to listen until a packet header is received. The tool listener extracts, from the packet header, a source address, a destination address and a frame type. The tool listening device adds the source address, the destination address, and the frame type to a data structure, and transmits the data structure to an external device, where the data may be visualized. The tool listening device is further configured to select another radio channel from the discovery channel hopping sequence.

Abstract: Coordinated timing networks are dynamically merged into a single coordinated timing network. This merge occurs without taking down any of the servers. Each server of the merged coordinated timing network has the same coordinated timing network identifier (CTN ID), and the merged coordinated timing network has one selected primary time server. Optionally, the merged coordinated timing network may include a backup time server and an arbiter.

Abstract: A Node-B sends a polling message to a wireless transmit/receive unit (WTRU). The WTRU sends an uplink synchronization burst in response to the polling message without contention. The Node-B estimates an uplink timing shift based on the synchronization burst and sends an uplink timing adjustment command to the WTRU. The WTRU then adjusts uplink timing based on the uplink timing adjustment command. Alternatively, the Node-B may send a scheduling message for uplink synchronization to the WTRU. The WTRU may send a synchronization burst based on the scheduling message. Alternatively, the WTRU may perform contention-based uplink synchronization after receiving a synchronization request from the Node-B. The WTRU may enter an idle state instead of performing a handover to a new cell when the WTRU moves to the new cell. A discontinuous reception (DRX) interval for the WTRU may be set based on activity of the WTRU.

Abstract: Provided is a fraudulent message detection device that detects a fraudulent message in a bus network and includes: a resynchronization detector that detects an edge of a signal on a bus in the bus network and determines whether to perform resynchronization, so as to adjust a sampling point in a one-bit period; a transmission and receiving control unit that obtains a first logical value and a second logical value in a one-bit period after the resynchronization detector determines to perform the resynchronization, the first logical value being a logical value at a sampling point used before the edge is detected, the second logical value being a logical value at a sampling point after the resynchronization is performed; a comparator that compares the first and second logical values; and a fraud detection processing unit that executes post-fraud-detection processing, when the first and second logical values do not coincide.

Abstract: A system for controlling accesses to network enabled devices includes a network interface over which a hub communicates with network enabled devices, a processor, and a multilayer access control layer. The access control layer includes instructions that, when executed by the processor, cause the processor to detect, at the hub, a request representing an attempt by an application executing on a remote host device to access a network enabled device communicatively coupled to the hub, characterize the request according to a user of the remote host device, the application making the attempt, and the network enabled device, and determine whether to allow or deny the request based upon the characterization and a plurality of rules. The rules may include definitions of access rights, with respect to the network enabled device, for users, applications, commands or queries made by applications, remote host devices, and network domains.

Abstract: A system for use with an OFDM-receiver. The system comprising a frequency-offset-correction-block; and a sub-band-demapping-block. The sub-band-demapping-block is configured to receive an input-signal and determine within the input signal: one or more allocated-frequency-sub-bands allocated to convey an information-signal; and one or more unallocated-frequency-sub-bands. The sub-band-demapping-block can then provide the allocated-frequency-sub-bands and the unallocated-frequency-sub-bands to the frequency-offset-correction-block.

Abstract: A method conducting financial transactions over a computerized network, where a plurality of client computers and servers, which are connected to one another, over a network, solve for a set of transaction vectors that change a routing of capital between any transaction participants in a manner that deviates from the original intended transaction vectors between any original sending participant or any original receiving participant; and wherein movement of the capital between transaction participants is optimized for efficiency.

Abstract: According to some embodiments, a method in a wireless device operating in dual connectivity comprises determining a synchronization type associated with a dual connectivity operation; determining a maximum timing advance value based on the determined synchronization type; receiving a timing advance value from a network node; determining an adapted timing advance value using the received timing advance value and the determined maximum timing advance value; and transmitting an uplink radio signal using the adapted timing advance value.

Abstract: A method of transmitting data between an electronic transmitter device and an electronic receiver device connected together by a data link, the method comprising the steps of: sending the data in the form of at least three identical frames sent in succession and each associated with respective checkdata calculated on the frame in question; and the electronic receiver device verifying the validity of the received frames as they are being received and making the first valid frame available for processing while ignoring the others.

Abstract: A method of transmitting data between network devices over a non-deterministic network with a multiple channel access method, wherein it is not possible to determine, whether a network device can access the non-deterministic network, wherein the non-deterministic network comprises a plurality of network devices. The method includes the steps of: synchronising clocks of individual network devices of the plurality of network devices with each other, dividing time available for transmitting the data into timeslots, designating respective pairs of consecutive timeslots to the individual network devices of the plurality of network devices, wherein an individual network device transfers data only during the respective pairs of timeslots designated to it and evaluating, whether a network device of the plurality of network devices shall retransmit data, which it has already transmitted during a first timeslot of a pair timeslot, within the second timeslot of the pair of timeslots.

Abstract: A latest status record of an object in a local storage node is obtained as a local status record of the object. The status record includes a name of an operation changing the object, a timestamp of the operation changing the object, a first status flag, and a second status flag. The first status flag indicates whether a synchronization of the object from current object storage node to another object storage node is executed. The second status flag indicates whether a synchronization of the object from another object storage node to the current object storage node is executed. The latest status record of the object is obtained of the object in from a remote object storage node as a remote status record of the object. A synchronization of the object is executed based on the local status record and the remote status record.

Abstract: Data Block Transmission with Variable Retransmission Feedback Time For communicating data between a transmitter (10) and a receiver (14), wireless transmission of data blocks is implemented on the basis a retransmission protocol with variable value of a feedback time. The feedback time defines a time interval between transmission of one of the data blocks (22) and transmission of a feedback message (23) indicating whether the data block (22) was successfully received. The transmitter (10) or the receiver (14) determines the value of the feedback time. Depending on the determined value of the feedback time, the transmitter (10) controls transmission of the data block (22) to the receiver and/or the receiver (14) controls reception of the data block (22) at the receiver (14). The transmitter (10) may for example be a base station of a mobile network, and the receiver (14) may be a terminal device connected to the mobile network.

Abstract: A Node-B sends a polling message to a wireless transmit/receive unit (WTRU). The WTRU sends an uplink synchronization burst in response to the polling message without contention. The Node-B estimates an uplink timing shift based on the synchronization burst and sends an uplink timing adjustment command to the WTRU. The WTRU then adjusts uplink timing based on the uplink timing adjustment command. Alternatively, the Node-B may send a scheduling message for uplink synchronization to the WTRU. The WTRU may send a synchronization burst based on the scheduling message. Alternatively, the WTRU may perform contention-based uplink synchronization after receiving a synchronization request from the Node-B. The WTRU may enter an idle state instead of performing a handover to a new cell when the WTRU moves to the new cell. A discontinuous reception (DRX) interval for the WTRU may be set based on activity of the WTRU.

Abstract: A wave pipeline includes a plurality of data paths, a clock signal path, and a return clock signal path. Each data path includes an input node, an output node, and a data stage between the input node and the output node. Each data path has a different delay between the input node and the output node. A first data path of the plurality of data paths has a first delay and each of the other data paths of the plurality of data paths have a delay less than the first delay. The clock signal path provides a clock signal to the data stage of each data path. The return clock signal path provides a return clock signal from the data stage of the first data path. The return clock signal triggers data out of the data stage of each data path of the plurality of data paths.

Abstract: A method is disclosed for use by a network element comprising a plurality of ports for communicating a common clock signal with one or more neighboring network elements. The method comprises, for at least one port of the plurality of ports, determining, while the port is in a predefined listening mode, whether the port is connected with a neighboring network element; and calculating, when the port is connected, a respective clock phase delay value between the network element and the neighboring network element. The method further comprises, based on a role assigned to the network element from a plurality of predefined roles, assigning a clock signal synchronization role to the port. The network element is configured to communicate the common clock signal using the clock phase delay value and using the clock signal synchronization role.

Abstract: In one embodiment, a method comprises receiving, by a network device, one or more advertisement messages comprising timing information describing a quality of a network clock that is originated by a master clock device at a root of a directed acyclic graph (DAG); the network device executing an objective function for the DAG providing an optimized loopless time topology for the network clock, synchronized to the master clock device, based on the timing information; and the network device attaching to a parent device in the DAG based on the objective function, for optimized generation of the network clock by the network device.

Abstract: A method for communication includes receiving in a network interface controller (NIC) from a host processor, which has a local host memory and is connected to the NIC by a local bus, a remote direct memory access (RDMA) compress-and-write command, specifying a source memory buffer in the local host memory and a target memory address. In response to the command, data are read from the specified buffer into the NIC, compressed in the NIC, and conveyed from the NIC to the target memory address.

Abstract: A circuit generates a number of oscillations. The circuit includes a first branch with at least one delay line introducing symmetrical delays on rising edges and on falling edges and at least one asymmetrical delay element introducing different delays on rising edges and on falling edges. The circuit further includes a second branch looped back on the first branch and including at least one delay line introducing symmetrical delays on rising edges and on falling edges.

Abstract: A method to provide a cyber attack resistant and fault tolerant precision clocking scheme for wide area critical infrastructure networks through what is called Distributed Time Source Validation, DTSV, is provided, which is a distributed algorithm and signaling mechanism for a network to detect a compromised time source or sources in a multiple master clock system. The method includes providing a local clock signal, receiving in a node R1 an external clock signal from an external source, C or S1, estimating based on the local clock signal and the external clock signal timing parameters associated with the first node and the external source, comparing the timing parameters to detect any Mutual Clock Discrepancy (MCD) between the first node and the external source, and distributing any detected MCD in the network.

Abstract: Fault tolerant and redundant grand master clock scheme may reduce or eliminate precision time transition caused by a network link or device failure. A primary synchronization message may be sent by a primary grandmaster clock and one or more backup synchronization message may be sent by respective backup grandmaster clocks. The primary and backup grandmaster clocks may be concurrently operated. The primary and backup synchronization messages may be sent to an end station over a network. The end station may derive a local clock based on one, some, or all of the received messages. The end station may or may not distinguish between the messages based on the clock source. The end station may validate messages received from a particular clock source.

Abstract: Methods, computer systems, and computer program products for configuring ports of interconnected communications equipment include, defining configuration parameters for at least one port of a plurality of ports of a plurality of interconnected communications devices; defining a group of the at least one port of the plurality of ports of the plurality of interconnected communications devices into a configuration group; and creating an explicit link mirroring the defined configuration parameters of the at least one port of the plurality of ports of the plurality of interconnected communications devices to the defined configuration group of at least one port of the plurality of ports of the plurality of interconnected communications devices, such that changes made to the defined configuration parameters are replicated and synced to the defined configuration group.

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 technique for facilitating clock recovery in a node of a packet-based network is disclosed. The node is synchronized with other nodes based on a master-slave clock mechanism. A list of backup master clock node is maintained for the node, which includes at least one backup master clock node for the node, and in response to occurrence of a synchronization related event, a master clock node of the node is switched from the current master clock node to a backup master clock node selected from the list. A master clock node reselection message is generated and transmitted to the switched backup master clock node for the switched backup master clock node to reselect its master clock node.

Abstract: A method for synchronizing clocks, including: receiving at least two clock signals, where the at least two clock signals are sent by a bidirectional clock tracking link respectively corresponding thereto; setting two or more clock signals coming from a same network element into a same clock source group; selecting one clock signal in a same clock source group as a currently tracked clock signal; and if the currently tracked clock signal belongs to the clock source group, respectively sending a standby clock signal carrying quality-level do not use information by using the bidirectional clock tracking link respectively corresponding to each of the clock signals in the clock source group. The present invention achieves the effect that in the scenario where there are two or more bidirectional clock tracking links between two network elements, a clock tracking loop will not be generated.

Abstract: There is provided an information processing apparatus including a virtual clock controller configured to update a first virtual clock on the basis of a system clock, and a synchronization part configured to perform given data synchronization processing with another information processing apparatus on the basis of the first virtual clock and a second virtual clock that is updated by the another information processing apparatus.

Abstract: According to an embodiment, a wireless communication unit includes a media access control (MAC) unit. The MAC unit includes a clock unit, an acquisition unit and a calculation unit. The clock unit includes a register which stores periodically counted-up first time information. The acquisition unit acquires a statistic for reception quality information on the received packet. The calculation unit normalizes the second time information, weights the normalized second time information using a time weight based on the statistic, and calculates a time correction value for correcting the first time information, using the weighted and normalized second time information. The time weight increases with increasing link stability indicated by the statistic.

Abstract: A method of configuring communications management on board an aircraft comprising the implementation of a mechanism for electing a master equipment item in a network of computer equipment items in charge of aircraft-ground communications of the aircraft and of configuring communication management according to the master equipment item. The method enables the applications in charge of the aircraft-ground communications to be distributed between the networked computer equipment items.

Abstract: A system includes a plurality of sensing devices, a first multiplexer, a plurality of local return clock signal paths, a second multiplexer, and a data latch. Each sensing device outputs data onto a respective local data path in response to a clock signal on a clock signal path. The first multiplexor passes data from a selected local data path to a global data path. Each local return clock signal path is coupled to the clock signal path at a respective sensing device such that each local return clock signal path is routed along with a respective local data path. The second multiplexor passes a return clock signal from a selected local return clock signal path corresponding to the selected local data path to a global return clock signal path. The data latch latches the data on the global data path into the data latch in response to the return clock signal on the global return clock signal path.

Abstract: When transmitting data from a data relay apparatus to a mobile station through a plurality of base stations, the plurality of base stations add sequence numbers to the data and transmits the data with the sequence number. The data relay apparatus transfers a first data and second data to the mobile station through different base stations among the plurality of base stations, in which the data relay apparatus transfers the first data received before the second data to one base station and transfers the second data while adding thereto information indicating the reception order of the first and second data. Each of the plurality of base stations, when the data transferred from the data relay apparatus contains the information added thereto, adds the sequence number to the data based on the information and transmits the data with the sequence numbers to the mobile station.

Abstract: The present invention provides a time setting system and method thereof that are capable of correctly setting time if a delay occurs in the transmission of time information. In the system for setting a master time outputted from a master apparatus to a slave time of a slave apparatus that counts time independently of the master apparatus, the slave apparatus has transmission section for transmitting master time request information to the master apparatus via a network and the master apparatus has an allowable range information acquisition section for acquiring allowable range information indicative of an allowable time in which the master time may be set to the slave time of the slave apparatus and transmission section for transmitting the master time and allowable range information to the slave apparatus.

Abstract: A method of operating a mobile station in a packet transfer mode includes receiving a distribution timing advance message on a control channel from a base station. The distribution timing advance message contains a plurality of mobile station identifiers and associated timing advance values. One of the mobile station identifiers is identified as corresponding to the mobile station. The timing advance value associated with the identified one of the mobile station identifiers is determined. The timing of an uplink transmission to the base station is then adjusted responsive to the timing advance value. Related mobile stations, methods of operating a base station subsystem to communicate timing advance values to a plurality of mobile stations, base station subsystems, and methods of operating a serving GPRS support node to control communication of timing advance values by a base station subsystem are also disclosed.

Abstract: Methods, devices, and computer program products for synchronization of wireless devices in a peer-to-peer network are described herein. In one aspect, a method for synchronizing a wireless communication apparatus is provided. The method includes receiving, at the wireless communication apparatus, one or more messages including one or more received time values. The method further includes updating a time value of a clock signal of the wireless communication apparatus to a value derived from the received time values in response to determining that a magnitude of a difference between the time value and the derived time value is greater than a threshold.

Abstract: The present disclosure is directed at a method and apparatus for generating a metric for use in any one or more of lock detection, SNR estimation, and modulation classification. To generate the metric, an input angle in the form of a symbol phase or a difference in symbol phases is used to evaluate a base function. The base function relates possible metrics to possible input angles using a triangle wave having its maxima or minima at ideal input angles, and the other of its maxima or minima at angles midway the ideal input angles. Described are embodiments that are one or more of non-data aided; that may be implemented relatively efficiently in hardware; that can function using one sample/symbol; that can achieve relatively good detection certainty using relatively few estimates; and that can be used to implement modulation classifiers, lock detectors, and SNR estimators that are resilient to imperfections in automatic gain control.

Abstract: Transfer of differential timing over a packet network is provided. A transmitting service interface receives a service clock and is coupled to a receiving service interface through a network backplane. A primary reference clock is provided to time the network backplane. The primary reference clock and the service clock are used to synthesize a copy of the service clock connected to the transmitting service interface. A first control word containing an error differential between the service clock and the synthesized copy of the service clock is generated and transmitted through the network backplane via a packet. The first control word, together with the primary reference clock, is used to recreate the service clock for timing the receiving service interface.

Abstract: The exemplary embodiment of the present invention provides a method of synchronizing a femtocell base station securing time synchronization of a femtocell base station by allowing the femtocell base station to transmit a symbol to a terminal belonging to the femtocell by performing the time synchronization with a preamble signal when the femtocell base station receives the preamble signal from the macrocell base station in an orthogonal frequency division multiple access (OFDMA) communication system in which a femtocell is present in a macrocell.

Abstract: A method for determining data enabling a plurality of secondary base stations to time their transmissions to a mobile station within a timing range. The mobile station obtains time delays of transmissions from each of the secondary base stations in reaching the mobile station, and determines time delay differences between the time delays and a reference time delay associated with a primary base station. The mobile station transmits the time delay differences to the plurality of secondary base stations. Each secondary base station receives the difference between its own transmission time delay and the reference time delay, compares the difference with a time range, and corrects the timing of its transmissions if the difference is outside of the time range.

Abstract: Systems and methods for mapping an iterative time-based data acquisition (DAQ) operation to an isochronous data transfer channel of a network. A time-sensitive buffer (TSB) associated with the isochronous data transfer channel of the network may be configured. A data rate clock may and a local buffer may be configured. A functional unit may be configured to initiate continuous performance of the iterative time-based DAQ operation, transfer data to the local buffer, initiate transfer of the data between the local buffer and the TSB at a configured start time, and repeat the transferring and initiating transfer in an iterative manner, thereby transferring data between the local buffer and the TSB. The TSB may be configured to communicate data over the isochronous data transfer channel of the network, thereby mapping the iterative time-based DAQ operation to the isochronous data transfer channel of the network.

Abstract: Certain aspects of a method and system for speed negotiation for twisted pair links in fiber channel systems are disclosed. Aspects of a method may include communicating data between fiber channel host devices communicatively coupled via a twisted pair link based on a common speed negotiated between the fiber channel host devices. At least one available speed may be determined for the communication of data between the fiber channel host devices over the twisted pair link. The determined available speeds for each of the fiber channel host devices may be exchanged via at least one fast link pulse signal. The common speed negotiated may be a highest available speed for the communication of data between the fiber channel host devices.

Abstract: A method of synchronizing a local estimation of global network time of a receiving node on a network to a global network time reference is provided. The free running nodes receive precise time protocol synchronization messages and determine a ratio and an offset based on time data extracted from the messages.

Abstract: Techniques are described to provide a device and network of devices that collect distributed coordinated timestamps from distributed time counters in a multi-module or multi-integrated circuit system. The interconnect between the modules can be a single-wire or a two-wire interconnect. The modules communicatively coupled to the interconnect can use a collision-avoidance protocol for triggering the broadcasting of timestamps among the modules as well for allowing all modules to transmit their timestamps. Timestamps from multiple clocks can be transmitted by all modules and then collected and compared to produce correction factors to clock signals of each module to potentially achieve distributed clock synchronization in multiple independent modules or integrated circuits.

Abstract: A method and a system for controlling a compressed mode in a macro-diversity state are provided by the disclosure, wherein the method comprises that a terminal and a serving node B determine a compressed mode, wherein the compressed mode comprises: transmission gap pattern sequence information; the terminal and the serving node B start or stop the compressed mode, the terminal or the serving node B indicates a current compressed mode state to a related node B, and the related node B performs compressed mode operation according to the current compressed mode state. According to the disclosure, the problem that the execution state of the compressed mode of the terminal and a network side cannot be synchronized is solved, normal operation of the compressed mode of the terminal is guaranteed, and the service quality of the terminal and the performance of the system are improved.

Abstract: A method for synchronizing a plurality of clocks arranged within a plurality of nodes of a packet-switching network comprises comparing parameters that relate to the plurality of clocks in order to determine master-slave relationships between the plurality of clocks, and exchanging time-stamped messages over the packet-switching network each time between a master clock and an associated slave clock to make the associated slave clock subservient to the master clock. A node of the packet-switching network comprises a frequency source controlled by a synchronous physical layer technology. The parameters that relate to a clock of the node comprise a parameter that relates to the frequency source to determine the master slave relationships based on one property of the frequency source.

Abstract: A system for synchronizing nodes in a wireless network comprises a first node and a second node. The first node comprising a transmitter, a receiver, and a first time keeper. The second node comprising a transmitter, a receiver, a second time keeper, a timing error measurer for making a timing error measurement between the first time keeper and the second time keeper. The second timekeeper is adjusted to target minimizing the timing error measurement.

Abstract: The present invention is a system and method for enabling multicast synchronization of initially unicasted content. Multiple unicast streams are synchronized in order to convert the unicast streams into a multicast stream. Each unicast stream may be accelerated or slowed down in relation to a reference stream to a common point within each stream upon which the unicast streams are replaced by a multicast stream of the same content.

Abstract: The embodiments herein relate to a method in a communications network comprising a communications link connecting a first device to a second device. The communications link comprises an upper layer having a variable delay and a lower layer having a constant delay. The first device comprises a first clock and the second device comprises a second clock. The communications network synchronizes the first clock via the lower layer of the communications link with the second clock. The communications network determines, at the second device, a residence time for a first message when transmitted from the first device to the second device via the upper layer of the communications link.