JohnAllen <johnbenal...@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 Remove .spam.sux to reply. _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
