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

David L. Mills mills at udel.edu
Fri Aug 1 14:40:36 UTC 2003

```Christopher,

How did you come to the conclusion the destination timestamp is zero?
That would require your onboard clock to be zero as well.

Dave

Christopher J. Holland wrote:
> Hi,
>
> Ok, then this is the correct way.
> Originate Timestamp T1 = (Packet) Originate Timestamp
> Transmit Timestamp T3 = (Packet) Transmit Timestamp
> Destination Timestamp T4 =  The destination timestamp is scarfed by the
> making the total of four timestamps.
>
> So, does scarfed  mean that the Destination TimeStamp is 0?
>
>
> TIA,
> "David L. Mills" <mills at udel.edu> wrote in message
> news:bgd0ed\$qhc\$1 at dewey.udel.edu...
>
>>Christopher,
>>
>>that packet, making the total of four timestamps. You may wish to light
>>up the architecture briefing at the NTP project page linked from
>>www.ntp.org.
>>
>>Dave
>>
>>Christopher J. Holland wrote:
>>
>>
>>>Hi,
>>>
>>>Thanks, but that isn't what I was asking. You already pointed it out.
>>>I was just lucky to join the list when you did post it.
>>>
>>>I am trying to relate T1,T2,T3 & T4 to the Packet Structure.
>>>
>>>***** Is this the correct way? *******************************
>>>Originate Timestamp T1 = (Packet) Reference Timestamp
>>>Receive Timestamp T2 = (Packet) Originate Timestamp
>>>Transmit Timestamp T3 = (Packet) Receive Timestamp
>>>Destination Timestamp T4 = (Packet) Transmit Timestamp
>>>
>>> ***** Is this the correct way? *******************************
>>>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
>>>>>
>>>>>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>     |                                                               |
>>>>>     |                   Reference Timestamp (64)                    |
>>>>>     |                                                               |
>>>>>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>     |                                                               |
>>>>>     |                   Originate Timestamp (64)                    |
>>>>>     |                                                               |
>>>>>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>     |                                                               |
>>>>>     |                    Receive Timestamp (64)                     |
>>>>>     |                                                               |
>>>>>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>     |                                                               |
>>>>>     |                    Transmit Timestamp (64)                    |
>>>>>     |                                                               |
>>>>>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>
>>>TIA,
>>>Thanks,
>>>"David L. Mills" <mills at udel.edu> wrote in message
>>>news:bgbbil\$be4\$1 at dewey.udel.edu...
>>>
>>>
>>>>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)                    |
>>>>>     |                                                               |
>>>>>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>>