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Internet Security and Firewall Policies
Published in Steven F. Blanding, Enterprise Operations Management, 2020
In addition to those protocols previously discussed are the following: Serial Line Internet Protocol. The serial line Internet protocol (SLIP) is used to exchange IP traffic with a device, usually a workstation, that is running the proper protocols but without a separate address. It is used to connect workstations to hosts or to Internet service providers through the dial-switched network. It is analogous to an extension cord or a remote.Point-to-Point Protocol. The point-to-point protocol (PPP) is similar to Serial Line Internet Protocol, but is associated with leased lines. It is usually used to connect a single system to a boundary or “edge” node.Network Time Protocol. The network time protocol (NTP) is used to set and synchronize the system clocks of Internet nodes. It is able to synchronize all systems in a network to within milliseconds of each other, i.e., to within the accuracy and precision of the system clocks themselves.Secure Protocols. Recently, secure versions of these protocols have been specified, and reference implementations of these protocols are available for Unix systems.
Smart Grid Technologies
Published in Stuart Borlase, Smart Grids, 2017
Time synchronization over communications networks is mainly achieved through NTP/SNTP (Network Time Protocol, Simple Network Time Protocol) or IEEE 1588 also called PTP (Precision Time Protocol). While NTP was defined back in 1985, IEEE 1588 is more recent and was first published in 2002 and revised in 2008. Besides the technical differences of the two protocols, their main differentiator is the accuracy they can provide: SNTP can provide an accuracy of tens of milliseconds across a WAN, while PTP can provide submicrosecond accuracy on an LAN. SNTP is mainly intended to run over a WAN but can also be run on an LAN in which case the accuracy can improve to a couple of hundreds of microseconds under ideal conditions. Conversely, PTP is restricted to an LAN and requires some specific hardware to achieve high accuracy. From a smart grid point of view, SNTP is mainly used for control and monitoring applications, while PTP is mostly used for protection applications.
Communications Systems
Published in Stuart Borlase, Smart Grids, 2018
Mehrdad Mesbah, Sharon S. Allan, Donivon D. Hettich, Harry Forbes, James P. Hanley, Régis Hourdouillie, Marco C. Janssen, Henry Jones, Art Maria, Mehrdad Mesbah, Rita Mix, Jean-Charles Tournier, Eric Woychik, Alex Zheng
Time synchronization over communications networks is mainly achieved through NTP/SNTP (Network Time Protocol, Simple Network Time Protocol), or the IEEE 1588 standard, also called PTP (Precision Time Protocol). While NTP was defined back in 1985, IEEE 1588 is more recent and was first published in 2002 and revised in 2008. Besides the technical differences of the two protocols, their main differentiator is the accuracy they can provide: SNTP can provide an accuracy of tens of milliseconds across a WAN down to a couple of hundreds of microseconds in a LAN, while PTP can provide sub-microsecond accuracy. From a smart grid point of view, SNTP is mainly used for control and monitoring applications, while PTP is mostly used for protection applications.
Timing Synchronization System on RF-Driven Neutral Beam Injection System
Published in Fusion Science and Technology, 2022
Y. Li, C. D. Hu, Y. Z. Zhao, Q. L. Cui, X. L. Shu, Y. H. Xie, W. Liu
Network time synchronization refers to synchronizing the clock of each node to a stable and high-precision time source through the network so that the whole system can achieve clock consistency. At present, the network clock synchronization system generally uses the Network Time Protocol (NTP); the synchronization accuracy can reach only millisecond level. NTP is a protocol based on TCP/IP and User Data Protocol (UDP) network transmission and adopts the method of application layer synchronization for network time synchronization. The synchronization protocol is mainly defined by RFC 1305, “Network Time Protocol (Version 3) Specification, Implementation and Analysis.” It can solve the time synchronization problem between devices on complex network topologies. For some systems with low time synchronization accuracy requirements, using NTP for time synchronization is more economical and practical, and the implementation method is relatively simple.
The Reach and Impact of the Remote Frequency and Time Calibration Services at NIST
Published in NCSLI Measure, 2018
Some NIST customers, especially those in the financial sector, require the highly accurate time they receive from NIST to be distributed to computers within their organization or network, so that transactions and files can be accurately time stamped. These customers utilize the NISTDC, which typically keeps time within 10 ns of the UTC(NIST) time scale, as the reference for the Time Code Output service (76104C). This service can distribute time codes to the customer’s server or client computers via either the Network Time Protocol (NTP) or Precision Time Protocol (PTP).