[EMAIL PROTECTED] wrote:
The ntp server is not synchorinizing with remote internet servers, it
is relying only on the local clock, so I do not think "clock-hopping"
is the problem.
We measure the 60ms delay as follows. A node sends a UDP packet from
the server A to the client B. At the MAC layer on A, we put the
timestamp of A in the packet. At the MAC layer at B, we put the time
stamp at B. Finally at the application layer at B, we receive the
packet and print the time stamps. These timestamps show a gap of almost
60ms, while NTP claims an offset of 4us. This is what confuses me.
See RFC 1305 p. 100 for an explanation of how offset and round trip
delay are calculated.
Let T1 be the client timestamp in the request,
T2 be the server's receive timestamp,
T3 be the server's transmit timestamp, and
T4 be the clien'ts receive timestamp.
Then:
Offset = ((T2-T1) + (T3-T4))/2
Delay = (T4-T1) - (T3-T2)
The above is taken from RFC 1305. The RFC has a diagram and greek
letters to further clarify the subject.
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