[ntp:questions] is USB inherently evil, or only if something else is on the bus?
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Wed Aug 8 22:50:48 UTC 2012
Rick Jones wrote:
> wondering about some of the previous discussion about USB
> and how it is perhaps not "evil" but considered quite
> sub-par for serving-up the PPS signal.
> Is that unsuitability inherent in USB, so it matters not
> whether there is anything else on the USB, or is it more
> a case of being "bad" generally only when other things
> are on the same USB? I'm still looking to go serial,
> but was wondering.
Just, higher 7 less deterministic latency than a real serial port.
> If I happen to have say four servers in a location which
> might loose its connectivity to the outside world I
> probably don't want those servers to fall-back on
> LOCAL(0) right? Would configuring each to have the other
> three as "peer" entities be the way to go?
> Pointers to the fine manual for any of the above would be welcome.
When you have a group of computers on a LAN configured for
orphan mode, and they lose contact with remote servers,
the LAN client/servers will follow each other around.
Then when the remote servers can be contacted again,
the remote servers are selected.
e.g. I use something similar to this on all PCs / Devices
# ALL (Clients and/or Servers)
tos cohort 1 orphan 11
restrict default limited kod nomodify notrap
restrict source nomodify
keys "/etc/ntp.keys" # e.g. contains: 123 M YOUR_MD5_KEY
manycastclient 188.8.131.52 key 123 preempt
multicastclient 184.108.40.206 key 123 preempt
.... and add Server, Pool, Peer and RefClock lines
to your Primary Server (& Secondary if you have one).
e.g. peer clepsydra.dec.com iburst # Corp HP Western Research Laboratory, Palo Alto, CA
server ntp-cup.external.hp.com iburst prefer # Corp Cupertino CA (SF Bay area)
server clock.via.net iburst # Local to Palo Alto, CA
server clock.isc.org iburst # Local to Palo Alto, CA
server 220.127.116.11 iburst # AS71 peer 7018
server sl-crs1-ria-0-3-3-0.sprintlink.net iburst # AS71 peer 1239
server tardy.usa.hp.com iburst # LAN
pool 0.hp.pool.ntp.org iburst preempt # HP doesn't actually appear to have a vendor pool?
pool 0.dec.pool.ntp.org iburst preempt # DEC doesn't actually appear to have a vendor pool?
pool us.pool.ntp.org iburst preempt # Regional pool in lieu of a vendor pool?
You might want to contact for advice:
"timer at cup.hp.com" & "ntp-admin at wrl-mail.hpl.hp.com"
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