[ntp:questions] UK report on GPS vulnerabilities seems to overlook NTP

jimp at specsol.spam.sux.com jimp at specsol.spam.sux.com
Tue Mar 8 18:11:37 UTC 2011

JohnAllen <johnbenallen at gmail.com> wrote:
> Maybe I read this too quickly, but the report published today by the
> UK Royal Academy of Engineering (see
> http://www.raeng.org.uk/news/publications/list/reports/RAoE_Global_Navigation_Systems_Report.pdf
> and also the BBC coverage at http://www.bbc.co.uk/news/science-environment-12668230)
> seems to be saying that many organisations are vulnerable to GPS
> failures because their IT systems rely on GPS for precise time.
> Can this be true? I would have thought that most systems are using
> NTP, and synchronising with diverse enough time sources that
> unavailable or incorrect GPS time would not cause short-term problems.
> The relevant part of the report is on pages 13-14, where it says:
> "GNSS timing is important for telecommunications applications.
> Synchronous
> technologies are much more efficient than asynchronous technologies
> but require a
> time source with appropriate accuracy, stability and reliability to
> operate effectively
> or at all, and GNSS can provide this. While ground-based clocks are
> accurate enough
> for this purpose (especially with the availability of chip scale
> atomic clocks (CSAC)),
> the synchronisation of many such clocks is problematic. GPS allows the
> derivation of
> synchronised UTC through resolving the signals from a number of
> satellites at a
> known position. Only a ‘good guess’ of the current time is required
> and quartz clocks
> have therefore been adequate for this process making synchronous time
> keeping
> significantly more cost effective.
> The use of time can be split into three clear and separate aspects:
> frequency
> control, time of day and common epoch (usually UTC) time slot
> alignment (also
> known as ‘Phase’).
> Stability of radio communications transmission, constant digital traic
> low, time
> slot alignment and traditional services over next generation Ethernet
> based
> infrastructure are some of the features that good time and timing
> bring to
> communications networks.
> Financial systems increasingly need precise time stamping to
> prioritise trades and
> to provide an audit trail."
> NTP is not mentioned anywhere in the report.

Nor would I expect it to be.

There is a big difference between keeping a computer's time of day clock
set to the current time (NTP) and maintaining timing or frequency control
in a telecom system.

Jim Pennino

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