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Is there have any difference between this two terms, 'Clock Synchronization' and 'Time Synchronization' in a network? I understand that when clock frequency has corrected to run in same pace is called 'Syntonization'. And Synchronization + Syntonization = Network Synchronization.

I noticed that 'Clock Synchronization' and 'Time Synchronization' has been synchronously used. But I was wonder, if there have any technical differences?

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  • The clock pulses on a network link actually have nothing to do with time, but timing. A clock pulse on a network link is really for both sides to know what is a bit on the wire. That has nothing to do with what time it is. – Ron Maupin♦ Jan 12 '17 at 15:18
  • I presume, the terms 'clock synchronization' and 'clock pulse' is not same. Therefore, the explanation regarding pulse is not satisfying my asking. But yes, the pulse is something that you have said. – Fida Hasan Jan 13 '17 at 0:57
  • The interfaces need clock synchronization so that the pulses are interpreted correctly. The timing of the clock pulses on the link must be the same on both ends. That is clock synchronization, and it has nothing to do with the time. There are many clocks involved in computing that have nothing to do with the time. For instance, a CPU has a clock for pacing of the instructions, and its timing must match that of other parts, e.g. memory, but that has nothing to do with the time. – Ron Maupin♦ Jan 13 '17 at 1:01
  • Now it make sense! Yes, I do agree. However, my question was something like that, whether 'clock sync' and 'time sync' can synonymously be used? In academia, in almost every cases i found them to use as synonym. Apart from this two there are some other term, for example, <br/> Frequency Sync: when the leading edge of the pulses are at same pace, but not at the identical moment. (sounds like what you wanted to say. It is also known as rate synch. <br/> – Fida Hasan Jan 13 '17 at 1:34
  • Phase Sync: when the leading edge of the pulses are at identical moment. <br/> time sync: Leading edge of the pulses are at the identical moment and identical time. <br/> Network Syc: rate correction + offset correction. <br/> But there are no differences I have found very explicitly outlined between time and clock sync rather they always comes as a synonym. If you can send me any link of academic paper would help. Regards. – Fida Hasan Jan 13 '17 at 1:34
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At least in the context of network devices clock synchronization tends to refer to synchronous circuits where a constant time signal has to be maintained so that two devices can know the precise rate at which data is being transmitted and received. If the respective clocks of two devices are skewed then the integrity of the circuit will suffer. As such it's fairly typical for one device to derive its clock from a neighbor which, in turn, either works from an internal oscillator or an external source.

Time synchronization is generally referring to maintaining accurate time/data values on a number of devices. An example of this would be through the use of the Network Time Protocol (NTP) which allows for synchronization of time/date to global standards with at least a fair degree of precision. Keeping accurate time is incredibly important for logging/forensic purposes but also crucial for certain cryptographic and security processes (among other things).

So - you can think of clock synchronization as being akin to making sure the second hand on two clocks are ticking at the same rate while time synchronization is making sure that the absolute second, minute and hour hands of the two clocks keep reading the same. As such it's possible for two devices to have clock synchronization but be set to different times and, within some definition, two unsynchronized devices to have very closely synced time/dates (or calendars as they're sometimes known).

As an aside - it's possible to get high-resolution timing devices that can both act as an accurate source of time/date information as well as providing high-resolution reference clocking but these functions can also potentially be had independently.

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  • That's why I have added the other term, Syntonization in reference of Network Synchronization. Your explanation of 'clock synchronization' is in line with the definition of 'syntonization'. In academia, I found that both clock and time synchronization have used synonymous. Write up starts with time synchronization in its title suddenly switched to clock synchronization and vice versa. – Fida Hasan Jan 12 '17 at 6:16
  • Yes - keeping the timing of two sides of a synchronous circuit is syntonization. The part of the assertion in your question that isn't quite right is the idea that network synchronization is synchronization and syntonization when, in fact, they're often effectively independent. Protocols like NTP exist precisely because maintaining syntonization at Internet scale is practically intractable and that periodically updating (read: correcting) non-syntonized clocks ends up being a baseline requirement. – rnxrx Jan 12 '17 at 6:28
  • I appreciate your contribution and view of explanation. Actually while I just surfing net and gone through several academic articles, I found that they switched from Time to Clock and Clock to Time frequently without any notice. This link distinguishes some part of the terminology (first figure, frequency, phase, time) where 'clock synchronization' term is absent. So, I can assume that 'time' is replaceable. > aventasinc.com/whitepapers/WP-Timing-Sync-LTE-SEC.pdf – Fida Hasan Jan 12 '17 at 6:47
  • Yes - I would agree that the terms are incorrectly used interchangeably in a lot of industry literature. The LTE world is kind of a different animal in some ways as there is a much more centralized topology of devices that necessarily need to operate in a tightly coupled synchronous manner. This is quite different than most of the world of Ethernet/IP networking and general compute. There is a very entertaining subculture of time geeks focused on PTP, NTP and various implementations. They usually come front and center with leap seconds and such. – rnxrx Jan 12 '17 at 7:03

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