Abstract: With the advent of internet-of-things (IoT)-based home automation systems, time synchronization techniques for low power sensor modules are in high demand. The constrained application protocol (CoAP) was recently standardized for sensor networks by IETF and is becoming widely adopted for home automation systems by ETSI, OMA, and oneM2M. The network time protocol (NTP) is not applicable to home automation systems due to its limited computing resources. This paper proposes a lightweight time synchronization algorithm for CoAP-based home automation system networks. The CoAP option field and a shim header are used to include time-stamps in the home automation system. The proposed scheme can thus be applied to both IP-based and non-IP-based home automation systems. In experiments with several household devices having non-IP communication interfaces, experimental results show that the proposed technique gives an average error of 1 ms and a network overhead reduction of 17% when compared to the ideal NTP service.

Abstract: This document describes Network Time Security (NTS), a collection of measures that enable secure time synchronization with time servers using protocols like the Network Time Protocol (NTP) or the Precision Time Protocol (PTP). Its design considers the special requirements of precise timekeeping which are described in Security Requirements of Time Protocols in Packet Switched Networks [RFC7384].

Abstract: Communication networks rely on time synchronization information generated by base station equipment (either the Global Navigation Satellite System receiver or rubidium atomic clock) to enable wireless networking and communications. Meanwhile, the time synchronization among base stations depends on the Network Time Protocol. With the development of mobile communication systems, the corresponding time synchronization accuracy has increased as well. In this case, the use of sparsely distributed-high-precision synchronization points to synchronize time for an entire network with high precision is a key problem and is the foundation of the enhanced network communication. The current receiver equipment for China’s digital synchronous network typically includes dedicated multi-channel GPS receivers for communication; however, with the development of GPS by the USA, network security has been destabilized and reliability is low. Nonetheless, network time synchronization based on Beidou satellite navigation system timing devices is an inevitable development trend for China’s digital communications network with the establishment of the independently developed BDS, especially the implementation and improvement of the Beidou foundation enhancement system.

Abstract: The Network Time Protocol version 4 (NTPv4) defines the optional usage of extension fields. An extension field, as defined in RFC 5905, is an optional field that resides at the end of the NTP header and that can be used to add optional capabilities or additional information that is not conveyed in the standard NTP header. This document updates RFC 5905 by clarifying some points regarding NTP extension fields and their usage with Message Authentication Codes (MACs).

Abstract: Denial of Service (DoS) attacks are a type of interruption (malicious and/or unintended) that restrict or completely deny services meant for legitimate users. One of the most relevant DoS attacks is Distributed Denial of Service (DDoS) attack which is a variant of DoS, but on a larger scale using previously compromised, malware infected computers known as “bots” or “zombies”. DDoS attack occurs by generating large amounts of traffic towards an intended victim. This paper focuses on analyzing a variant of DDoS attacks known as Network Time Protocol (NTP) Distributed Reflective Denial of Service (DRDoS) attack. The impact of the attack will be measured in the utilization of processor, memory, network and ping of most relevant devices. Further focus is on the host and network based layered “defense in-depth” of NTP DRDoS attack mitigation techniques.

Abstract: In the recent past, the development of applications and protocols for the Internet of Things (IoT) made a big leap forward. New approaches have emerged to adopt IoT technologies in the realm of industrial automation. This development is also referred to as Industrial Internet of Things (IIoT) or Industry 4.0. It is predicted for the number of smart interconnected devices participating in automation systems to grow significantly in the future. However, the industrial domain introduces new requirements for IoT technologies regarding the timeliness of interactions. Current IoT protocols, like the Constrained Application Protocol (CoAP), do not yet provide real-time behavior for the inter-device communication. In our previous work, we have already proposed a real-time extension for CoAP that enables deterministic network behavior through a TDMA-based approach. We have shown that the proposed mechanisms for time synchronization, time slot management, and access control can be realized purely software-based. However, a central instance is needed as a time server. This introduces a Single Point of Failure (SPoF) to the system, limiting the robustness and scalability of the approach. In this paper, we introduce a concept for a distributed time server for CoAP. The proposed concept includes a refined time synchronization mechanism as well as strategies to select multiple time servers and share information between them. Furthermore, the described amendments to the real-time extension are integrated into the lightweight platform-independent jCoAP communication stack and evaluated in a multi-device real-world test bed.

Abstract: This document describes a convention for using the Cryptographic Message Syntax (CMS) to protect the messages in the Network Time Security (NTS) protocol. NTS provides authentication of time servers as well as integrity protection of time synchronization messages using Network Time Protocol (NTP) or Precision Time Protocol (PTP).

Abstract: This document describes how to reach the objectives described in the Network Time Security (NTS) specification when securing time synchronization with servers using the Network Time Protocol (NTP).

Abstract: The invention relates to the technical field of space-time consistency of all simulation real objects in a network, and discloses a high-precision network time unifying device and method. The device employed by the method comprises a time server and a client. The time server is connected with the client through the network, and the time server is formed by the connection of a PCI interface and a PCI time unifying demodulation card. A radio frequency input end of the PCI time unifying demodulation card is connected with a GPS/BD dual-mode antenna through a signal line. A data input end of the PCI time unifying demodulation card is connected with an IRIG-B time code signal source through a signal line. The high-precision network time setting and network frequency modulation enables the time bias of each network client to be less than or equal to 1ms. The device can provide in-network overall consistent natural time or simulation time for a plurality of application progresses or users, and can achieve the accelerating or slowing of the in-network overall simulation time. The device is low in cost, and is small in network bandwidth occupation and computer resource occupation.

Abstract: Now a day’s Wireless Sensor Network are used in various applications where full or partial time synchronization plays a vital role. Basic aim of Time synchronization is to achieve equalization of local time between all the nodes within the network. This paper proposes a new framework for time synchronization problem of wireless sensor network. Time synchronization protocols are very popular and widely used in WSN now days. An analysis has been performed utilizing the proposed frame work, which leads to a conclusion that it consumes less energy than the traditional time synchronization protocols: Reference Broadcast Time Synchronization and Time-Sync Protocol for Sensor Network. It has been observed that the proposed frame work do not require a Global Positioning System or any other external system to coordinate with time, as a typical Network Time Protocol for wireless sensor system uses. The proposed time synchronization protocol is categorized as peer to peer, clock-correcting sender- receiver network-wide synchronization protocol depending upon the characteristics of WSN. The maximum probability theory is used in order to analyze the clock offset. It was observed that resynchronization interval is required to achieve a specific level of synchronization correctness. Results are obtained by simulating the WSN on NS2 to demonstrate the energy efficient feature of the proposed protocol.

Abstract: A method is provided for synchronizing clocks on a plurality of audio playback devices. The method includes receiving a broadcast/multicast acknowledgement packet from a synchronization agent at a first audio playback device of the plurality of audio playback devices. A first timestamp representing a time when the acknowledgement packet was received by the first audio playback device is recorded. A broadcast/multicast timestamp packet is received from a time server at the first audio playback device. The timestamp packet includes a second timestamp representing a time when the time server received the acknowledgement packet from the synchronization agent. A local clock time on the first audio playback device is updated based on the first timestamp and the second timestamp. The method enables clock synchronization among the plurality of audio playback devices for synchronized playback of streamed audio via the plurality of audio playback devices.

Abstract: Using a testbed with reference timestamping, we collected timing data from public Stratum-1 NTP servers during the leap second event of end-June 2015. We found a wide variety of anomalous server-side behaviors, both at the NTP protocol level and in the server clocks themselves, which can last days or even weeks after the event. Out of 176 servers, only 61% had no erroneous behavior related to the leap second event that we could detect.

Abstract: This project describes hardware design and implementation of low-cost smart alarm clock based on Arduino platform, which uses passive infrared sensor (PIR) to detect sleep states of users. Sleep is not just a passive process. People can achieve different states during the night, which are known as Hypnagogia (state from wakefulness to sleep), NREM (non-rapid eye movement), REM (rapid eye movement), Hypnexagogium (awakening state) and dreaming. The main goal for this developed smart alarm clock is to detect these states and adjust alarm time to the best possible moment, when people are in awaking state or in light sleep. Awaking in these states is quite better and people feel much more refreshed. Hardware of this developed alarm clock is composed from LCD LED display, real-time (RTC) clock unit, temperature and humidity sensor, photosensitive module for detection of daytime, touch sensor and WiFi module for time synchronization from NTP (Network Time Protocol) servers. This Smart alarm clock could be used for better and more effective awakening for users.

Abstract: In this work, we present an initial step towards enabling TT scheduling on a real COTS multicore platform P4080. It takes into account inter-core interferences in the on-chip network and the memory sub-system. We propose an approach comprising a runtime mechanism and an offline phase. For the runtime mechanism, we propose two servers running on each core-processing time server and memory access server implemented using built-in hardware monitors. Jointly, the two servers on each core, enforce slot-level offline computed server budget reservations, thereby limiting the maximum inter-core interferences introduced and experienced by each task considering different inter-core interference latencies. In the offline phase, we propose a procedure that can be used by any offline scheduler to compute the bound on variability in execution time of each task while allowing different slot-level memory access server budget reservations. We also did a preliminary bare-metal implementation of our proposed runtime mechanism on a real COTS multicore platform P4080. Overall, our proposed method facilitates integration of COTS multicore platforms in TT systems, while maintaining features of TT architecture like slot-level determinism, clock synchronization, etc.

Abstract: Clock synchronization protocols are very widely used in IP-based networks. The Network Time Protocol (NTP) has been commonly deployed for many years, and the last few years have seen an increasingly rapid deployment of the Precision Time Protocol (PTP). As time- sensitive applications evolve, clock accuracy requirements are becoming increasingly stringent, requiring the time synchronization protocols to provide high accuracy. This memo describes a multi-path approach to PTP and NTP over IP networks, allowing the protocols to run concurrently over multiple communication paths between the master and slave clocks, without modifying these protocols. The multi-path approach can significantly contribute to clock accuracy, security and fault tolerance. The multi-path approach that is presented in this document enables backward compatibility with nodes that do not support the multi-path functionality.

Abstract: The invention discloses an OpenStack network traffic monitoring method. An OpenStack network environment comprises an open-source virtual switch, an Internet protocol flow information export (IPFIX) module, a network time protocol module and a plurality of switches, wherein the open-source virtual switch is taken as an L2 agent; the network time protocol module is used for synchronizing time of the open-source virtual switch and the plurality of switches in a network; the plurality of switches ToR are required to support functions of the IPFIX module based on data streams and support functions of the network time protocol module; OpenStack virtual and physical network traffic forwarding conditions are monitored through the IPFIX module; and information collected by the IPFIX module is converted into various pieces of forwarding information of an OpenStack network. Through adoption of the method, a visualization degree of the OpenStack network is increased, and an OpenStack network management difficulty and a network fault locating difficulty are lowered.

Abstract: The invention discloses a time synchronization method among wireless devices The procedures of the method comprise: determining a wireless device as a time server in a wireless local area network, taking other wireless devices in the wireless local area network as time customers; sending first data packets comprising current first time points to the time server by the time customers, after the time server receives the first data packets, sending second data packets to the time customers by the time server, wherein the second data packets comprise first time points, second time points at which the time server receives the first data packets and third time points at which the time server sends the second data packets; when the time customers receive the second data packets, obtaining fourth time points at which the second data packets are received; calculating the time difference between the time customers and the time server by the time customers according to the time data The invention also discloses a time synchronization system among wireless devices According to the invention, the problem that the multiple wireless devices play non-synchronously is solved

Abstract: The invention relates to an IMA processor system clock synchronization method. The method includes the following steps that: 1) after powering on, physical timer signals are selected as initial reference time, and satellite clock signals and data link clock signals are selected as corrected reference clock signals in the work process of time servers, and one kind of signals selected from the satellite clock signals and the data link clock signals are adopted as timekeeping circuit reference clock; 2) the time servers carry out timekeeping, generates time information required by a system, and distributes the time to various subsystems and functional modules through an FC network; 3) human-computer interface input is carried out; 4) FC network time synchronization is carried out: the FC network time synchronization is realized through FC network time synchronization primitive; and the IOM module time servers complete time services between an IMA processing system functional module and the other system equipment through the FC switching network; and 5) 1553B bus clock synchronization is carried out. The IMA processor system clock synchronization method provided by the invention meets the requirements of high time synchronization accuracy, small synchronization time delay and high time synchronization reliability, and is suitable for the clock synchronization of a new-generation aircraft high performance task system.

Abstract: In order to collect the corona current in multiple locations of HVDC transmission lines, a distributed synchronous data acquisition system is designed and implemented. The system comprises a time server and a plurality of subsystems, the time server and the client computers in subsystems form a local area network through a switch. The distributed synchronous data acquisition system is designed based on NTP(Network Time Protocol), the Client/Server work mode is used in the system. At regular intervals, the time synchronization between clients and server is executed, the server sends collection command to each subsystem. The synchronization scheme of the corona current measurement system is realized by the software programming of the server and the client, and the synchronization precision can reach 1.725ms, which provides a solution for the large-scale distributed synchronous data acquisition.

Abstract: The invention provides a cluster time synchronization method, a cluster and a time synchronization system. The method comprises the step of selecting at least one node in a cluster as a server node, configuring the other nodes as client nodes, and configuring time synchronization addresses for the client nodes according to the address of each server node. The method also comprises the step of sending a first synchronization request to an external time server by the server node and receiving standard time sent by the time server; carrying out synchronization on own clock by the server node according to the standard time; sending second synchronization requests to the server node by the client nodes according to the configured time synchronization addresses; feeding back current time corresponding to own clock to the corresponding client nodes by the server node according to the received second synchronization requests; and carrying out time synchronization by the client nodes according to the current time fed back by the server node. According to the scheme, the time synchronization efficiency can be improved.

Abstract: A trusted time service is provided that can detect resets of a real-time clock and re-initialize the real-time clock with the correct time. The trusted time service provides a secure communication channel from an application requesting a timestamp to the real-time clock, so that malicious code (such as a compromised operating system) cannot intercept a timestamp as it is communicated from the real-time clock to the application. The trusted time service synchronizes wall-clock time with a trusted time server, as well as protects against replay attacks, where a valid data transmission (such as transmission of a valid timestamp) is maliciously or fraudulently repeated or delayed.

Abstract: A system and method for setting time and date in a device (e.g., a set top box (614), or similar client device) through a network connection when a network time standard server (606, 620) (e.g., a NTP server) is unavailable (e.g., blocked or blacklisted) are provided. The system and method of the present disclosure involves sending (404) a request over a network from a device for information from an Internet address (618), receiving (406) a packet (500) from the Internet address (618) in response to the request, extracting (408) time and date information from a header (502) in the packet (500), and using the extracted time and date information to set (416) the current time and date for the device.

Abstract: In recent years, downtime and information loss problems of server computers have become more critical. Even if a server has antivirus and CPU overload checking programs, it may occasionally be broken or slowed down. Hypothetically, there are possible indications of the problems under specific external situations such as high temperature, low fan speed, and extreme main board vibration. In order to recognize the correlation between external conditions and the overloaded problems, a monitoring computer collects data from external sensors. By using an accelerometer, an anemometer, and a temperature sensor, the monitoring algorithm is able to predict the target computer's status. A web application has been developed to help server managers to remotely know how server computers are operating. This paper proposes a monitoring algorithm to diagnose server overload for a target computer, based on the Fast Fourier Transform, multivariate linear regression, and learning algorithms. As a result, this paper suggests that a monitoring algorithm can be implemented with an artificial neural network that warns of possible malfunction cases.

Abstract: The invention provides a network time protocol (NTP) message security authentication method and an NTP message security authentication device. The method comprises the following steps: when there is a need to send a first NTP authentication message, determining an authentication serial number corresponding to the first NTP authentication message, wherein the authentication serial number is an increasing serial number; and carrying the authentication serial number in the first NTP authentication message and sending the first NTP authentication message to opposite-end equipment, wherein the authentication serial number is used for the opposite-end equipment to judge whether the received NTP authentication message is a legitimate message. By implementing the embodiments of the invention, the security of NTP message interaction is improved, and message replay attack is avoided.

Abstract: Network Time Protocol(NTP) is one of the oldest popular networking protocol for packet switched data networkto synchronize the time effectively. This paper represents interface of NTP for an embedded system to serve as client. Practical testing has been performed on electrical protection relay as an example embedded power protection device considering a client. Here, we exploit protection relay which need accurate time stamps for real time operation. These kinds of relay or power grid do not have Internet connectivity due to there is an issue for synchronizing clock in them that is why NTP is adopted for highly accurate time synchronization in protection relay. Lightweight implementation of NTP in user space which efficiently work as original NTPdaemon.

Abstract: The invention provides a synchronization method and a synchronization system for a standard time and a fighting time of cross-platform terminals of multiple types. The synchronization method comprises the steps that: a network topology structure of a time server and a plurality of terminal devices is established; the plurality of terminal devices extracts standard time information and adjust the standard time of the plurality of terminal devices according to the standard time information; the time server sets fighting time information according to an exercise process and pushes the fighting time information to the terminal devices; and the plurality of terminal devices receive the fighting time information and adjust the fighting time of the plurality of terminal devices according to the fighting time information. The system comprises the time server and the plurality of terminal devices, and each terminal device comprises a plurality of fixed terminals and a plurality of mobile terminals. The time synchronization method provided by the invention is used for calibrating and synchronizing the standard times and the fighting times of the terminals in military actions or experiences and guaranteeing the time uniformity in the military actions.

Abstract: The invention discloses a method and a system for timing each vehicle-mounted system of a subway based on a vehicle-mounted information service network. The method comprises steps: S1, a ground timing wireless network system and the vehicle-mounted information service network are built; S2, the vehicle-mounted information service network builds a communication link with the ground timing wireless network system to acquire the time of the ground timing wireless network system; and S3, the vehicle-mounted information service network uses the acquired time to time all vehicle-mounted systems of the subway in a unified mode. The time of a subway vehicle is acquired by the vehicle-mounted information service network from the time server in the ground timing wireless network system via a wireless, the acquired time is not influenced by the environment, the subway vehicle timing precision is high, the time unity of each vehicle-mounted system of the subway is good, and the timing speed is quick.

Abstract: The application provides a data correction method and an electronic device. The method comprises: when detecting that a virtual machine is paused in operation due to the execution of a backup operation, reading and storing first current time of a plurality of to-be-selected time sources; and when the virtual machine performs a recovery operation on backup content of the backup operation, selecting a target time source from the to-be-selected time sources according to a first preset rule, reading second current time of the target time source, and comparing the second current time with the first current time to obtain a target time difference value, namely, a virtual machine pause time, of a process from the backup operation to the recovery operation, wherein at the moment, no matter how long the virtual machine pause time is, an NTP server is constructed in a current virtual environment. According to the method, system time of the virtual machine is accurately corrected by utilizing the target time difference value to solve the time shift problem caused in the backup and recovery operations and ensure accurate and reliable output time.

Abstract: A system for transmitting low latency, synchronised audio includes an audio source, a processor, a controller and a sink zone with a DAC. The processor selectively resamples the audio source in order to output a data packet for transmission to the sink zone that has a maximised payload size while packet frequency remains a whole number. In an embodiment the audio source is a CD player and the audio is upsampled from 44.1 kHz to 48 kHz. The resulting data packet has 128 frames, a payload size of 594 bytes, a packet frequency of 375Hz, and is smaller than the maximum transmission unit (MTU) (see table 2 on page 7). The audio output is transmitted using the Internet Protocol (IP) and is based on UDP Multicast and point-to-point UDP and TCP. A common time clock is implemented across the DACs of sink zones using Network Time Protocol (NTP) or Precision Time Protocol (PTP), and each packet carries a presentation time (fig. 3).