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Does anyone out there use a hardware appliance clock instead of the Internet?
Taking time direct from a stratum 1 server offends against several of NTP's design principles.
1. Accuracy: You have no way of evaluating the time signals you receive. Every clock goes wrong occasionally, and even if the clock is accurate, you are vulnerable to network delays. For this reason the official reference implementation (http://www.ntp.org) is designed to compare several servers and synchronise with the most reliable at any given time.
2. Stratification: There's a limited number of stratum 1 servers and they are likely to be heavily loaded. In general you shouldn't link to one unless you are operating at least three secondary servers offering time synchronisation to a large population. Most, including time-nw.nist.gov, have a restricted access policy and expect prior arrangement, or at least notification, before a regular connection is made. There are plenty of stratum 2 servers with open access policies (see list here: http://ntp.isc.org/bin/view/Servers/StratumTwoTimeServers), and many ISPs run one or more for their users. For obvious reasons it's better to link mainly to servers close to you in network topology.
3. Resilience: You are lost if the chosen server falls over, loses connectivity, or even moves to a different IP address.
Everyone's optimum solution will be different, but if you can run the ntp daemon on one or (preferably) several of your own machines, linking to each other and a selection of stratum 2 or stratum 3 servers, at least you have a reliable time source that's under your control. It will even run free for quite a time if you lose your internet connection.
1. Accuracy: You have no way of evaluating the time signals you receive. Every clock goes wrong occasionally, and even if the clock is accurate, you are vulnerable to network delays. For this reason the official reference implementation (http://www.ntp.org) is designed to compare several servers and synchronise with the most reliable at any given time.
2. Stratification: There's a limited number of stratum 1 servers and they are likely to be heavily loaded. In general you shouldn't link to one unless you are operating at least three secondary servers offering time synchronisation to a large population. Most, including time-nw.nist.gov, have a restricted access policy and expect prior arrangement, or at least notification, before a regular connection is made. There are plenty of stratum 2 servers with open access policies (see list here: http://ntp.isc.org/bin/view/Servers/StratumTwoTimeServers), and many ISPs run one or more for their users. For obvious reasons it's better to link mainly to servers close to you in network topology.
3. Resilience: You are lost if the chosen server falls over, loses connectivity, or even moves to a different IP address.
Everyone's optimum solution will be different, but if you can run the ntp daemon on one or (preferably) several of your own machines, linking to each other and a selection of stratum 2 or stratum 3 servers, at least you have a reliable time source that's under your control. It will even run free for quite a time if you lose your internet connection.
Styopa,
Those are good points & I appreciate the helpful links. It sounds like you are very knowledgeable about NTP. I appreciate your contribution!
Thanks for reading TechRepublic!
Sincerely,
David
Those are good points & I appreciate the helpful links. It sounds like you are very knowledgeable about NTP. I appreciate your contribution!
Thanks for reading TechRepublic!
Sincerely,
David
Don't forget to set time zone gentlemen!
router(config)# clock time-zone ZONE -h
http://www.cisco.com/en/US/docs/ios/12_3/configfun/command/reference/cfr_1g01.html#wp1033494
This link will also shows how we can configure DAYLIGHT if you are picky!
router(config)# clock time-zone ZONE -h
http://www.cisco.com/en/US/docs/ios/12_3/configfun/command/reference/cfr_1g01.html#wp1033494
This link will also shows how we can configure DAYLIGHT if you are picky!
thanks for this information
How much time Cisco router take to syn with NTP server in second
problem with me
when i power off my router and power it again
router can't syn with NTP server
i must reconfigure NTP server every time i reload my router to syn with NTP server
How much time Cisco router take to syn with NTP server in second
problem with me
when i power off my router and power it again
router can't syn with NTP server
i must reconfigure NTP server every time i reload my router to syn with NTP server
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