[ntp:questions] Re: Question about RFC-2030 SNTP Version4

David J Taylor david-taylor at blueyonder.co.uk
Sun Aug 3 08:30:21 UTC 2003


> Then T4 is the time at which the packet is received from the Server.

T4 is the formula, yes.  It is not in the packet.

> Actually, I noticed that Cyberkit keeps track of the Packet Times.
> Round Trip is calculated by the Client  (00:00:00:13:429 -
00:00:00:14:639)
> = 201 mS.
>
> Since, I know the Originating TimeStamp, I can just add the Round Trip
to
> get T4?
> T4 = T1 + 201mS
> T4 = 14039630149786221412 + 201000
> T4 = ???
> (Not sure if I should use the Fractional part, or the whole 64 bits in
my
> calculations?)

If you are handling the packet back from the server, you would note T4
when the packet arrived back with you, and use it to compute the round
trip.  It sounds as if some other software is doing that for you.  You
seem to be working backwards.  I would assume that you need the whole 64
bits for an accurate calculation.

> Once I am able to calculate d and t,
> Does the actual Time = T1(Originate Time) + Reference Clock Error +
Local
> Clock Offset?

What actual time?  There are four separate events in sending and receiving
a packet.  Which one are you trying to measure?

Cheers,
David





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