[ntp:questions] 2xGPS and 4x peers setup - disturbed by 5th and 6th peer

ardi peter.knezel at gmail.com
Fri Oct 31 09:22:27 UTC 2014


ardi wrote:
> having 2 GPS sources and 4 peers to each other (see below the setup),
> When turning on 5th and 6th peers, they disturb my setup.

> root at local.a2:~# ntpq -pn
>      remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> *local.xx   .GPS.               1 u    1   16  377    0.344   -0.037   0.046
> +remote.yy    .GPS.             1 u    -   16  377   34.258   -0.074   0.273
> -local.a1   xx.xx.xx.a1         2 u   12   16  377    0.286    0.043   0.015
> +remote.b1  yy.yy.yy.b1         2 u    3   16  377   33.555   -0.016   0.055
> -remote.b2  yy.yy.yy.b2         2 u    7   16  377   33.700    0.049   0.281
> +local-annoying.c1  yy.yy.yy.c1 2 u   12   16  377    0.216    0.043   0.044 <--why? how to get rid of it?
> +local-annoying.c2  yy.yy.yy.c2 2 u   12   16  377    0.326    0.043   0.03  <--why? how to get rid of it?

I'm missing why you find those two indicated so disturbing,

 They both have lower latency than remote.yy, remote.b1, remote.b2
 They both have lower jitter than remote.yy and remote.b2
 Their offset is in line with local.a1, and less than remote.b2 and remote.yy

Ardi: 
===ardi_start
let's skip this part - i can come back to this later.
===ardi_end
> Is it possible to restrict to those 4 peers only

If you really don't want them, just comment them out in your conf?

Ardi: 
===ardi_start
it is not question of commenting them - i can do it easily.
imagine a hypothetical situation, when somebody defines on network these extra 2 servers on purpose to "inflict" the existing setup.
I would like to avoid it by correct setup on those 2 GPS sources and 4 peers.
what i would like to achieve is that 4 peers getting time only from GPS sources
and from each other and all stratum3 servers and below can have the possibility to get time only from any of those 4 peers.
===ardi_end

> send time to stratums lower than 2 as well

Nothing prevents sending time to lower stratums;
-----------------^^^^^^^
 and at the client "by default, servers of all strata are acceptable".

  However "a stratum filter selects just those servers with stratum considered useful"

   tos cohort 1    will cause it to not "avoid servers operating at the same stratum as the client"

Ardi:
===ardi_start
i need to read a bit more about this option
===ardi_end

   peering a server will might make it more likely to be included
   prefering a server will also make it more likely to be included

Ardi:
===ardi_start
preferring a server is already included:
server xx.xx.xx.a2 minpoll 4 maxpoll 4 prefer
server xx.xx.xx.a1

===ardi_end
> xx.xx.xx.a2 .INIT. 16 u - 16 0 0.000 0.000 0.000 <---------does not get time from xx.xx.xx.a2!!!!

(Shrug), looks like it is not getting packets back from a2.
 If you get and decode the association information,
  you might find out more; e.g.
ntpq -crv -clpe -clas -c "rv &1" (or whichever association index number is relevant)

Ardi: 

===ardi_start
this is the output on xx.xx.xx.t1 (stratum3)

xx.xx.xx.t1 # ntpq -crv -clpe -clas -c "rv &1"
associd=0 status=0615 leap_none, sync_ntp, 1 event, clock_sync,
version="ntpd 4.2.6p2 at 1.2194-o Sun Oct 17 13:35:13 UTC 2010 (1)",
processor="x86_64", system="Linux/2.6.32-5-amd64", leap=00, stratum=3,
precision=-22, rootdelay=3.731, rootdisp=45.673, refid=xx.xx.xx.a1,
reftime=d7fdc99c.3e3638ca  Fri, Oct 31 2014  9:41:00.243,
clock=d7fdcbbd.e46ee56a  Fri, Oct 31 2014  9:50:05.892, peer=64477,
tc=10, mintc=3, offset=1.619, frequency=5.247, sys_jitter=1.649,
clk_jitter=1.024, clk_wander=0.071
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 xx.xx.xx.a2 .INIT.          16 u    -   16    0    0.000    0.000   0.000
*xx.xx.xx.a1 xx.xx.xx.xx    2 u  545 1024  377    3.243    1.619   1.649

ind assid status  conf reach auth condition  last_event cnt
===========================================================
  1 64476  8011   yes    no  none    reject    mobilize  1
  2 64477  963a   yes   yes  none  sys.peer    sys_peer  3
associd=64476 status=8011 conf, sel_reject, 1 event, mobilize,
srcadr=xx.xx.xx.a2, srcport=123, dstadr=xx.xx.xx.t1,
dstport=123, leap=11, stratum=16, precision=-22, rootdelay=0.000,
rootdisp=0.000, refid=INIT,
reftime=00000000.00000000  Mon, Jan  1 1900  1:00:00.000,
rec=00000000.00000000  Mon, Jan  1 1900  1:00:00.000, reach=000,
unreach=9616, hmode=3, pmode=0, hpoll=4, ppoll=4, headway=2,
flash=1600 peer_stratum, peer_dist, peer_unreach, keyid=0, offset=0.000,
delay=0.000, dispersion=15937.500, jitter=0.000, xleave=0.020,
filtdelay=     0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00,
filtoffset=    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00,
filtdisp=   16000.0 16000.0 16000.0 16000.0 16000.0 16000.0 16000.0 16000.0
xx.xx.xx.t1 #

it can be seen that it does not accept time from xx.xx.xx.a2
why should i need to define peer in its config?
===ardi_end

{My wild guess would be lack of trust by t1
  perhaps missing or mismatched keys.}

Ardi: 
===ardi_start
why should i need keys toward stratum3? in case a-case used, it works
      without keys ...
===ardi_end



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