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

Christopher J. Holland msnews at microsoft.com
Thu Jul 31 11:24:21 UTC 2003

```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)                    |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
|                    Transmit Timestamp (64)                    |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+