nanog mailing list archives
Re: NIST NTP servers
From: Eric Kuhnke <eric.kuhnke () gmail com>
Date: Wed, 11 May 2016 13:15:48 -0700
Cellular carriers also use GPS timing for many reasons that are not readily apparent at the layer 3 router/IP/BGP network level. One big need is RF related, back-to-back sector antenna frequency re-use with GPS synced timing on the remote radio heads, such as an ABAB configuration on a tower or rooftop site. The same with some much less costly near consumer grade WISP radio platforms and PTP radio systems nowadays. In such a configuration the GPS timing signal from the local GPS receiver (small cone shaped or puck antennas at the site) is actually the primary, and whatever NTP-based GPS signal the network node might have access to is secondary. On Wed, May 11, 2016 at 12:10 PM, Mel Beckman <mel () beckman org> wrote:
No, many cell carriers run their own completely independent timing networks. I support some head-ends where they have rubidium clocks and a T1-delivered time source. They do reference GPS, and many cell sites have GPS as a backup clock (you can see their conical antennas on the very top of the tower). But most cellular providers are very protective of their time sources. They’re also typically clocking SONET networks too, which requires BITS. -mel JAshworth said:CDMA and GSM are false diversity: both network types nodes *get theirtime*from GPS, so far as I know.On May 11, 2016, at 10:54 AM, Valdis.Kletnieks () vt edu wrote: On Wed, 11 May 2016 15:36:34 -0000, "Jay R. Ashworth" said:CDMA and GSM are false diversity: both network types nodes *get theirtime*from GPS, so far as I know.I'll make the fairly reasonable assumption that most readers of thislist havenetworks that span multiple buildings. If somebody is managing to figure out that you have a GPS in Building37, and aGPS-based CDMA up on the corner of Building 3, and the *other* 4 clocksatother locations and getting close enough to all of them at the same timetoconduct a successful spoofing attack, all just to move your time source a few seconds off.... ... then the fact that GPS is spoofable is probably *NOT* your biggest security problem.
Current thread:
- Re: NIST NTP servers, (continued)
- Re: NIST NTP servers Jared Mauch (May 10)
- RE: NIST NTP servers Chuck Church (May 10)
- Re: NIST NTP servers Gary E. Miller (May 10)
- Re: NIST NTP servers Mel Beckman (May 10)
- Re: NIST NTP servers Leo Bicknell (May 11)
- Re: NIST NTP servers Josh Reynolds (May 11)
- Re: NIST NTP servers Mel Beckman (May 11)
- Re: NIST NTP servers Jay R. Ashworth (May 11)
- Re: NIST NTP servers Valdis . Kletnieks (May 11)
- Re: NIST NTP servers Mel Beckman (May 11)
- Re: NIST NTP servers Eric Kuhnke (May 11)
- Re: NIST NTP servers Jean-Francois Mezei (May 12)
- Re: NIST NTP servers Mel Beckman (May 12)
- Re: NIST NTP servers Leo Bicknell (May 11)
- Re: NIST NTP servers Brandon Vincent (May 11)
- Re: NIST NTP servers Jon Meek (May 11)
- Re: NIST NTP servers Josh Reynolds (May 11)
- Re: NIST NTP servers Lamar Owen (May 13)
- Re: NIST NTP servers Mel Beckman (May 13)
- Re: NIST NTP servers Lamar Owen (May 13)
- Re: NIST NTP servers Mel Beckman (May 13)