[ntp:questions] Clarification on the org, rec, xmt header fields

Danny Mayer mayer at ntp.org
Thu May 21 13:38:00 UTC 2009

Hal Murray wrote:
>>> If you assume a client-server model, from the client's view
>>> there are 4 time stamps:
>>>   when the request leaves the client
>>>   when the request arrives at the server
>>>   when the response leaves the server
>>>   when the response arrives at the client
>> This model makes complete sense.  What I'm curious about is that I
>> would imagine that mode = 3, the only timestamp that is struck is the
>> 'request leaves' (org) but what I see is request arrives (rec) and the
>> response leaves (xmt) in the client packet.  What else is odd is that
>> the (org) is 10 milliseconds after the (rec) and the (xmt) is 8
>> minutes in the future! 
> One thing I wasn't clear on...  The code that adds the time stamps doesn't 
> know if it's client or server.

That's not true. If it is responding to a request then it's a server. If
it's initiating the request it's a client, unless it's a
broadcast/multicast server in which case it uses mode 5 packets. In
addition, a client sends mode 3 (client) packets and a server sends mode
4 (server) packets.


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