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Synchronous Ethernet. Synchronous Ethernet, also referred as SyncE, is an ITU-T standard for computer networking that facilitates the transference of clock signals over the Ethernet physical layer.

Synchronous Ethernet

This signal can then be made traceable to an external clock. Overview[edit] Mobile Networks require a kind of synchronization The aim of Synchronous Ethernet is to provide a synchronization signal to those network resources that may eventually require such a type of signal. The Synchronous Ethernet signal transmitted over the Ethernet physical layer should be traceable to an external clock, ideally a master and unique clock for the whole network. Unlike time-division multiplexing networks, the Ethernet family of computer networks do not carry clock synchronization information. SyncE was standardized by the ITU-T, in cooperation with IEEE, as three recommendations: ITU-T Rec.

Architecture[edit] Synchronization network model for Synchronous Ethernet, SONET and SDH Clocks[edit] Presentism (philosophy of time) Saint Augustine proposed that the present is analogous to a knife edge placed exactly between the perceived past and the imaginary future and does not include the concept of time.

Presentism (philosophy of time)

This should be self evident because, if the present is extended, it must have separate parts–but these must be simultaneous if they are truly a part of the present. According to early philosophers, time cannot be simultaneously past and present, and hence not extended. Contrary to Saint Augustine, some philosophers proposed that conscious experience is extended in time. For instance, William James said that time is "the short duration of which we are immediately and incessantly sensible".[1] Other early presenter philosophers include the Indian Buddhist tradition. Fyodor Shcherbatskoy, a leading scholar from the modern era on Buddhist philosophy, has written extensively on Buddhist presentism: "Everything past is unreal, everything future is unreal, everything imagined, absent, mental... is unreal. Unix time. Unix time passed 1,000,000,000 seconds in 2001-09-09T01:46:40Z.

It was celebrated in Copenhagen, Denmark at a party held by DKUUG (at 03:46:40 local time). Unix time (aka POSIX time or Epoch time), is a system for describing instants in time, defined as the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970,[note 1] not counting leap seconds. [note 2] It is used widely in Unix-like and many other operating systems and file formats. Due to its handling of leap seconds, it is neither a linear representation of time nor a true representation of UTC. [note 3] Unix time may be checked on most Unix systems by typing date +%s on the command line. Definition[edit] Two layers of encoding make up Unix time. As is standard with UTC, this article labels days using the Gregorian calendar, and counts times within each day in hours, minutes, and seconds. Vertical interval timecode. Vertical Interval Timecode (VITC, pronounced "vitsee" or "vits") is a form of SMPTE timecode embedded as a pair of black-and-white bars in a video signal.

Vertical interval timecode

These lines are typically inserted into the vertical blanking interval of the video signal. There can be more than one VITC pair in a single frame of video: this can be used to encode extra data that will not fit in a standard timecode frame. VITC contains the same payload as SMPTE linear timecode frame embedded in a new frame structure with extra synchronization bits and an error-detection checksum. The VITC code is always repeated on two adjacent video lines, one in each field. This internal redundancy is exploited by VITC readers, in addition to the standard timecode "flywheel" algorithm. A video frame may contain more than one VITC code if necessary, recorded on different line-pairs. As a practical matter, VITC can be more 'frame-accurate' than Linear timecode (LTC), particularly at very slow tape speeds on analog formats.

Network Time Protocol. NTP is intended to synchronize all participating computers to within a few milliseconds of Coordinated Universal Time (UTC).[1]:3 It uses a modified version of Marzullo's algorithm to select accurate time servers and is designed to mitigate the effects of variable network latency.

Network Time Protocol

NTP can usually maintain time to within tens of milliseconds over the public Internet, and can achieve better than one millisecond accuracy in local area networks under ideal conditions. Asymmetric routes and network congestion can cause errors of 100 ms or more.[2][3] The current protocol is version 4 (NTPv4), which is a proposed standard as documented in RFC 5905. It is backward compatible with version 3, specified in RFC 1305.

HTML5 Frame accuracy

White Rabbit. Memento: Adding Time to the Web. PRECISION TIME PROTOCOL. Microsystemes Timing & Synchronization solutions.