GPS Synchronization

Question

Hi All,
I am curious whether any routers or network devices synchronize with each other using GPS precise timing.  I know certain wireless cell phone networks utilize GPS for synchronization, but I am wondering if the same applies to wired networks (both ethernet and fiber). I say synchronization am referring to the router's internal clock/oscillator, not time-of-day.  All information is appreciated!
-Marc

Answer 1

Hi All,
I am curious
whether any routers or network devices synchronize with each other using
GPS precise timing.  I know certain wireless cell phone networks
utilize GPS for synchronization, but I am wondering if the same applies
to wired networks (both ethernet and fiber). I say synchronization am
referring to the router's internal clock/oscillator, not time-of-day. 
All information is appreciated!-Marc
Hi Marc,
As of today, two main solutions for real time clock synchronization:
– Router synchronized with a server using Network Time Protocol (NTP).
– Router synchronized directly with an external reference clock.
Before you buy a GPS clock for your router, make sure that Cisco supports the GPS product and that your router has the capability to obtain timing information from it?only certain routers support this feature. If your router does not support this feature, you need some other device to use as a master time reference. Most UNIX and Windows server products support external GPS devices.
If you have the Trimble GPS clock and are attaching it to the auxiliary port of a 7200 router, you need to configure the following on your router:
Router(config)# line aux 0
Router(config-line)# ntp refclock trimble pps none stratum 1
The ntp refclock command tells the 7200 that it has a Trimble GPS clock attached. The pps parameter indicates the type of pulse-per-second reference support: In the case of Trimble, this is set to none. Because this is probably the root time source for your network, you define the time source as a stratum service level of 1.
Hope to Help !!
Ganesh.H
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