nanog mailing list archives
Re: Interesting stratum 1 NTP clock
From: Jerry Scharf <scharf () vix com>
Date: Wed, 24 Jun 1998 11:08:11 -0700
Would a GPS hooked to the serial port of a Linux box do the same? Dirk On Mon, Jun 22, 1998 at 10:43:48PM -0700, Tony Li wrote:Folks who run NTP in their nets might wanna check out: http://www.coetanian.com/tss/tss100.htm This is a reasonably affordable, NTP-ready, GPS based stratum 1 chimer, complete with 10BaseT interface. It's also getting close to being plug-n-play. I've been beta testing one for a couple of weeks and it seems to chime reasonably well. Tony p.s. I have no finanical interest in this product or this company whatsoever. I'm just a time geek...
Any clock hooked up to a NTP server will make the server a stratum 1 server. It makes no statements about accuracy, just NTP hopwise closeness to truth. To NTP stratum, there is no difference between the thing Tony mentioned and a modem calling ACTS. Your accuracy of time will be much lower in the later cases, with what you proposed usually having errors in the single digit milliseconds. (rant #2) Lots of people say 'Why should I care about accurate time?' I have used NTP synchronized clock with both tcpdump and Cisco logging to chase problems. Sometimes I'm after big things, but other times I'm trying to figure out whether two things that are happening are the same or different. Being able to have time accurate to the few packet range is a real in separating these out. It's really hard to get there when you're talking about OC48s, but even fast ethernets have packets lasting in the 10s of microseconds. The nastiest problem I ever traced this way was a ethernet card on a bsd unix box that would occasionally drop interrupts when the system was under load. Being able to have two machines looking on the wires while the problem machine was acting as a router was the only way I found it. The events rarely lasted more than a couple milliseconds, so 10+ms timing just wouldn't have been good enough. Someone might have been able to guess the problem other ways, but with this I had tools to see the problem. So usually you don't need it, and if you don't have it you won't even believe you need it, but I have used it and always want it available. Not many (maybe none) customers are going to care below the 10s on milliseconds, but as a network engineers it could save you. (end or rant) jerry
Current thread:
- Interesting stratum 1 NTP clock Tony Li (Jun 23)
- Re: Interesting stratum 1 NTP clock Jerry Scharf (Jun 23)
- Re: Interesting stratum 1 NTP clock dirk (Jun 24)
- Re: Interesting stratum 1 NTP clock Jay R. Ashworth (Jun 24)
- Re: Interesting stratum 1 NTP clock Jerry Scharf (Jun 24)
- Re: Interesting stratum 1 NTP clock Tim Pozar (Jun 25)
- Humour Re: Interesting stratum 1 NTP clock Paul Mansfield (Jun 25)
- Re: Interesting stratum 1 NTP clock Robert E. Seastrom (Jun 25)
- Re: Interesting stratum 1 NTP clock Jerry Scharf (Jun 25)
- Message not available
- Re: Interesting stratum 1 NTP clock Tony Li (Jun 25)
- Re: Interesting stratum 1 NTP clock Stan Hanks (Jun 25)
- <Possible follow-ups>
- RE: Interesting stratum 1 NTP clock S.J.Brannon (Jun 24)
- RE: Interesting stratum 1 NTP clock David Newman (Jun 25)