[ntp:questions] NTP request retry?

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Mon Jan 27 02:09:34 UTC 2014


On 2014-01-26 12:08, Rob wrote:
> On a very quiet network, I observe that ntpd sometimes has a very
> high loss rate: reach is 6, for example.
>
> When using "ping" or any other protocol, no packet loss at all is
> observed.
>
> My hypothesis is that the ARP entry for the NTP server has timed out,
> and when ARP has to resolve an entry in some implementations the first
> packet is always lost (it is not cached pending a reply).
> When the cycle is 1024 seconds, the ARP entry has again timed out the
> next poll cycle and the issue is the same.
>
> Is there a way, short of switching to burst mode, to make ntpd retry
> a request when no reply is received e.g. within a second?
> It should only retry when there is no reply, and not more than e.g.
> 3 times (when still no reply it should simply wait for the next poll
> cycle)

You don't specify which system and devices you are using,
so here are a couple of articles about changing ARP timeouts:
http://www.embeddedsystemtesting.com/2013/01/arp-timeout-value-for-linux-windows.html
http://support.microsoft.com/kb/949589

-- 
Take care. Thanks, Brian Inglis


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