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Old 26th October 2015
pawkolor pawkolor is offline
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Hi I would ask about ntpd .As I'm rookie I do not understand why ntpd are listen on a lot of server .This server for my are strange .Why 4 but not 1 .
Code:
# fstat|grep ':123'
_ntp     ntpd        6942    6* internet dgram udp 37.8.230.0:17590 <-> 62.148.67.62:123
_ntp     ntpd        6942    8* internet dgram udp 37.8.230.0:3559 <-> 149.156.44.126:123
_ntp     ntpd        6942    9* internet dgram udp 37.8.230.0:11883 <-> 188.165.17.91:123
_ntp     ntpd        6942   10* internet dgram udp 37.8.230.0:38657 <-> 149.156.70.5:123

Last edited by ocicat; 26th October 2015 at 03:56 PM. Reason: Please use [code] & [/code] tags when posting command output.
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Old 26th October 2015
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jggimi jggimi is offline
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The protocol is designed to poll multiple servers, in order to account for network congestions and delays. The typical client will poll 3 or more servers. The OpenBSD default client configuration will use all IP addresses resolved by pool.ntp.org

See: https://en.wikipedia.org/wiki/Network_Time_Protocol

Last edited by jggimi; 26th October 2015 at 03:43 PM. Reason: added pool
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Old 26th October 2015
TronDD TronDD is offline
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The default configuration uses the pool.ntp.org servers. There are mutliple IPs returned from DNS with that domain name and using the 'servers' directive in the config, it will use all of them.

If you only want to use one, use the 'server' directive and whatever time server you want. Though, I usually use at least 2 servers so as not to have to completely trust one.

Tim.
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Old 26th October 2015
ocicat ocicat is offline
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Quote:
Originally Posted by TronDD View Post
Though, I usually use at least 2 servers so as not to have to completely trust one.
Just to add to TronDD's comments, accessing a pool or multiple servers helps ensure that local synchronization continues since if the active connection dies, another time source is known, configured, & readily accessed.

Multiple connections helps ensure reliability of the service provided by the protocol.

Last edited by ocicat; 26th October 2015 at 04:01 PM. Reason: clarify "reliability"
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Old 26th October 2015
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jggimi jggimi is offline
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Quote:
Originally Posted by ocicat View Post
Multiple connections helps ensure reliability...
...and accuracy. Multiple servers are polled and a "Selection and Clustering" algorithm is used. See Section 11.2 of RFC 5905.
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