[ntp:questions] Compensating for asymmetric delay on a per-peer/server basis?

Terje Mathisen terje.mathisen at tmsw.no
Fri Sep 12 09:58:05 UTC 2014


Rob wrote:
> Martin Burnicki <martin.burnicki at meinberg.de> wrote:
>> Rob wrote:
>>> Martin Burnicki <martin.burnicki at meinberg.de> wrote:
>>> When you serve thousands of clients, this tends to overflow the NAT
>>> table or stress the lookup code so much that it overloads the CPU.
>>
>> Haven't had such case, yet since my home NTP server doesn't serv 1000s
>> of clients, but sounds reasonable and should be kept in mind.
>
> It is sometimes a problem when you become member of the NTP pool.
>
I'm in that situation, but my ntp server is only announced on IPv6 where 
I do have a static/personal network range, and the server is also my 
gateway machine, i.e. it gets all port 123 packets forwarded without any 
NAT type source port rewriting.

I also have a nicely symmetric 50/50 fiber connection so I've stopped 
worrying about asymmetric delays. :-)

The best ipv6 link I've seen has been to a peer in South Africa, where 
we had many (100?) milliseconds of path delay, but our (gps-based) local 
times agreed within 100 us, i.e. a completely symmetric link all the 
way. :-)

Terje

-- 
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"



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