From Newsgroup: comp.protocols.time.ntp
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On Wed, 3 Apr 2024 at 09:26, Sameera Unnisa <
shaiksameer.sam90@gmail.com> wrote:
I have my ntp.conf as below
"pool -4 server1 true minpoll 6 maxpoll 10 iburst"
"pool -6 server1 true minpoll 6 maxpoll 10 iburst"
I could see after 3rd request the very next 4th request is happening
earlier than minpoll interval i.e 2^6 sec.
I see two distinct issues that may explain what you're seeing, but note
it's not entirely clear what you're seeing. You don't mention how you're seeing the requests. Are you looking at a packet capture? Does the early request occur on both IPv4 and IPv6?
1. The "pool" directive, as opposed to "server", instructs ntpd to attempt
to spin up as many associations for each hostname as possible, up until
ntpd has maxclock associations. With the above two lines being the
entirety of ntp.conf, I'd expect "tos maxclock 10" to be the default. If server1 resolves to more than one A (IPv4) or AAAA (IPv6) record, ntpd will solicit each in turn until 8 more associations are started. The "POOL" associations, as seen in `ntpq -p` output, count for 2 of the 10. At the
risk of wandering into the weeds a bit, the initial solicitation request appears just like a normal NTP client request, but the response is not processed for time. Instead, it results in starting an association with
the responding IP address and scheduling the next solicitation, if any.
2. "iburst" instructs ntpd to initially send a sequence of 6 requests at
least 2 seconds apart, assuming a response is received for each, to speed initial synchronization. If the association has become unreachable for
some time, iburst is activated again when responses are once again
received. Wandering in weeds again, stay away from "burst", which is
intended for synchronization occurring over an intermittent connection,
such over a dialup modem connection, where very high minpoll is used to
keep down costs by polling as infrequently as every 36 hours. It causes
the burst behavior on every query, rather than only initially.
If you continue to have problems, consider providing the output of `ntpq
-crv -w -clpeers` redacted of any names or addresses you wish.
Cheers,
Dave Hart
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<div dir=3D"ltr"><div dir=3D"ltr"><div class=3D"gmail_default" = style=3D"font-family:"trebuchet ms",sans-serif;font-size:s= mall"><span style=3D"font-family:Arial,Helvetica,sans-serif">On =
Wed, 3 Apr 2024 at 09:26, Sameera Unnisa <<a href=3D"mailto:shaik=
sameer.sam90@gmail.com">
shaiksameer.sam90@gmail.com</a>> = wrote:</span><br></div></div><div class=3D"gmail_quote"><blockquote = class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:=
1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"auto"><div = style=3D"font-size:12.8px" dir=3D"auto"><div style=3D"width:394.314p= x;margin:15px 0px"><div dir=3D"auto"><div dir=3D"auto">I =
have my ntp.conf as below</div><div dir=3D"auto"><br></div><div = dir=3D"auto">"pool -4 server1 true minpoll 6 maxpoll =
10 iburst"</div><div dir=3D"auto">"pool -6 server1 =
true minpoll 6 maxpoll 10 iburst"<br></div><div dir=3D"auto"><b= r></div><div dir=3D"auto">I could see after 3rd request =
the very next 4th request is happening earlier than minpoll =
interval i.e 2^6 sec.</div></div></div></div></div></blockquote><div=
class=3D"gmail_default" style=3D"font-family:"trebuchet = ms",sans-serif;font-size:small">I see two distinct =
issues that may explain what you're seeing, but note =
it's not entirely clear what you're seeing.=C2=A0 =
You don't mention how you're seeing the requests.=C2=A0 =
Are you looking at a packet capture?=C2=A0 Does the early =
request occur on both IPv4 and IPv6?</div><div class=3D"gmail_defaul=
t" style=3D"font-family:"trebuchet ms",sans-serif;font-siz= e:small"><br></div><div class=3D"gmail_default" style=3D"font-family= :"trebuchet ms",sans-serif;font-size:small">1.=C2=A0 =
The "pool" directive, as opposed to "server", =
instructs ntpd to attempt to spin up as many associations =
for each hostname as possible, up until ntpd has maxclock=C2=A0assoc= iations.=C2=A0 With the above two lines being the entirety =
of ntp.conf, I'd expect "tos maxclock 10" =
to be the default.=C2=A0 If server1 resolves to more than =
one A (IPv4) or AAAA (IPv6) record, ntpd will solicit each =
in turn until 8 more associations are started.=C2=A0 The =
"POOL" associations, as seen in `ntpq -p` output, =
count for 2 of the 10.=C2=A0 At the risk of wandering into =
the weeds a bit, the initial solicitation request appears =
just like a normal NTP client request, but the response =
is not processed for time.=C2=A0 Instead, it results in =
starting an association with the responding IP address and =
scheduling the next solicitation, if any.</div><div class=3D"gmail_d=
efault" style=3D"font-family:"trebuchet ms",sans-serif;fon= t-size:small"><br></div><div class=3D"gmail_default" style=3D"font-f= amily:"trebuchet ms",sans-serif;font-size:small">2.=C2=A0 = "iburst" instructs ntpd to initially send a sequence =
of 6 requests at least 2 seconds apart, assuming a response =
is received for each, to speed initial synchronization.=C2=A0 =
If the association has become unreachable for some time, =
iburst is activated again when responses are once again =
received.=C2=A0 Wandering in weeds again, stay away from =
"burst", which is intended for synchronization =
occurring over an intermittent connection, such over a dialup =
modem connection, where very high minpoll is used to keep =
down costs by polling as infrequently as every 36 hours.=C2=A0 =
It causes the burst behavior on every query, rather than =
only initially.</div><div class=3D"gmail_default" style=3D"font-fami= ly:"trebuchet ms",sans-serif;font-size:small"><br></div><d=
iv class=3D"gmail_default" style=3D"font-family:"trebuchet = ms",sans-serif;font-size:small">If you continue to =
have problems, consider providing the output of `ntpq -crv =
-w -clpeers` redacted of any names or addresses you wish.</div><div = class=3D"gmail_default" style=3D"font-family:"trebuchet = ms",sans-serif;font-size:small"><br></div><div class=3D"gmail_d=
efault" style=3D"font-family:"trebuchet ms",sans-serif;fon= t-size:small">Cheers,</div><div class=3D"gmail_default" = style=3D"font-family:"trebuchet ms",sans-serif;font-size:s= mall">Dave Hart</div></div></div>
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