[ntp:questions] NTP client basic

mills at udel.edu mills at udel.edu
Tue Mar 6 15:39:10 UTC 2007


Harlan,

SNTP doesn't do anything of the kind. It assumes only a single packet 
exchange resulting in four timestamps to determine the time and optional 
offset and roundtrip delay. As described in both RFC 1305 and the NTP4 
draft specification, the timestamps and certain state variables resist 
old duplicates and bogus packets. It is completely nonproductive to send 
a speculative number of packets and believe only the first one. If 
necessary, send a packet and wait a window turn, then send another one 
if lost.

Dave

Harlan Stenn wrote:

> Also,
> 
> As I recall SNTP may send out a bunch of requests but then it believes the
> first answer it gets.  Any other answers should just be dropped.
> 
> You should also be able to compare your transmit time to the transmit time
> in the return answers and throw away ones that don't match.
> 
> The spec should have a much better list of "how to handle packets".
> 
> H




More information about the questions mailing list