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

David L. Mills mills at udel.edu
Thu Jul 31 15:11:15 UTC 2003

```Christopher,

Please take a number. You are somewhere in the list of thirty-odd folks
who have found and reported that typo

d = (T4 - T1) - (T3 - T2)     t = ((T2 - T1) + (T3 - T4)) / 2.
(Correct Formula)

The correction is on file at the IETF. A draft update to RFC-2030 with
this correction and much new material is in review.

Dave

Christopher J. Holland wrote:

> Hi,
>
> I managed to decipher the 32 Bit Time to YYYY/MM/DD/HH//MM/SS format.
> Is there an RFC to tell you how to do that?
> Now, I am trying to figure out how to calculate Round Trip delay and Offset.
> I'm not sure which fields are which?
> Good thing I popped on this list at this time. I still had the old
> conversion formula!
>
>
> Does
> Originate Timestamp T1 = (Packet) Reference Timestamp
> Receive Timestamp T2 = (Packet) Originate Timestamp
> Transmit Timestamp T3 = (Packet) Receive Timestamp
> Destination Timestamp T4 = (Packet) Transmit Timestamp
>
> or does
> Originate Timestamp T1 = (Packet) Originate Timestamp
> Transmit Timestamp T3 = (Packet) Transmit Timestamp
> Destination Timestamp T4 = (Then where do I get this value? is it the
> Reference Timestamp?)
>
>
>       Timestamp Name          ID   When Generated
>       ------------------------------------------------------------
>       Originate Timestamp     T1   time request sent by client
>       Transmit Timestamp      T3   time reply sent by server
>
>    The roundtrip delay d and local clock offset t are defined as
>
>       d = (T4 - T1) - (T2 - T3)     t = ((T2 - T1) + (T3 - T4)) / 2. (Wrong
> Formula)
>       d = (T4 - T1) - (T3 - T2)     t = ((T2 - T1) + (T3 - T4)) / 2.
> (Correct Formula)
>
>       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>       |                                                               |
>       |                   Reference Timestamp (64)                    |
>       |                                                               |
>       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>       |                                                               |
>       |                   Originate Timestamp (64)                    |
>       |                                                               |
>       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>       |                                                               |
>       |                    Receive Timestamp (64)                     |
>       |                                                               |
>       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>       |                                                               |
>       |                    Transmit Timestamp (64)                    |
>       |                                                               |
>       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>