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

Christopher J. Holland msnews at microsoft.com
Sun Aug 3 01:33:31 UTC 2003


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

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

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

Thanks for your help,
"David J Taylor" <david-taylor at blueyonder.co.uk> wrote in message
news:cDJWa.481$Xq7.5875887 at news-text.cableinet.net...
> > There is no "Destination Timestamp" in the receive Packet, Just the
> > Reference TimeStamp.
> > So, what is meant by Destination Timestamp. I am not sure.
> > Perhaps T4 it is the Reference Timestamp,  but that aint working.
> > If you can plug in the values and come up with a correct answer.
> > Congratulations.
> > It is beyond my scope for the time being.
> >
> > Thanks for trying,
> Christopher, you are almost there - don't give up!
> If you think about it, there is no way in which the packet from server to
> client can know when it will be received by the client, so the packet on
> the wire cannot carry the T4 value!  The contents of the packet are made
> up at the server in the ways described, and the packet is then put on the
> wire.  At some point later, the packet is received by your client, and one
> of the first things your client should to do is to note the time of
> reception.  This will be the T4 value used in the formula.  The client
> will also have already noted the time of sending (T1) to allow it to make
> up the packet in the first place.  It will put that sending time in the
> Originate field of the packet, and that field should not be altered by the
> server.  The values for T2 and T3 for the formula come from the Receive
> and Transmit fields of the received packet, as filled in by the server.
> Cheers,
> David

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