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NPLTime® Services FAQs

Supporting industry, enabling innovation and delivering confidence

Frequently asked questions

What is the role of the service nodes in the NPLTime® infrastructure

The two NPL service nodes in Telehouse and Daisy, Reading are currently the only locations where users can access the fibre-based UTC(NPL) signal by subscribing to the NPLTime Access® service. The nodes also enable the NPLTime Certified® resellers to access the signal and deliver it using their own infrastructure to their end-point devices across various data centre locations in the London area. Users can then subscribe to the NPLTime Certified® service via our resellers. 

Can I connect to the NPLTime® services directly from the time source?  

No. Access to the UTC(NPL) signal is only available from the NPL service nodes in Telehouse and Daisy, Reading as part of the NPLTime Access® service or from the data centres where the NPLTime Certified® resellers have a certified end point device. These data centres are: Equinix LD4, Interxion, Basildon and Telehouse, Docklands. ​

Where can I sign up to NPLTime®? 

To subscribe to the NPLTime® services, please contact us.

Which locations is NPLTime® available from?

NPLTime Access® service is available from NPL’s service nodes at the following data centres: Telehouse North and Daisy in Reading. NPLTime Certified® service is available at Equinix LD4, Interxion, Basildon and Telehouse, Docklands.

What is the time source infrastructure for NPLTime® services?   

Both NPLTime Access® and NPLTime Certified® are referenced to the UK national timescale, UTC(NPL), at NPL in Teddington. From there they are distributed via Precision Time Protocol (PTP) over dark fibre to the NPL service nodes at Telehouse North, Docklands and Daisy, Reading.  

Is GNSS part of the NPLTime® infrastructure? 

No. NPLTime® infrastructure is completely independent of GNSS signals. The time source for the service is the UK’s national time scale and the signal is disseminated over dark fibre links to the NPL service nodes in Telehouse and Daisy, Reading.  

What happens if there is an incident on the network links between Teddington and Telehouse or Daisy? 

The NPLTime® service is monitored continuously from NPL, to ensure any service-affecting faults are detected in a timely manner. In addition, each service node is provided with a local caesium clock that is continuously steered to UTC(NPL) which can provide up to 30 days holdover in the event of total loss of PTP signal from NPL. 

How is resilience achieved for the NPLTime® services? 

Resilience at NPL and the service nodes is provided via two independent PTP feeds, referenced to two separate hydrogen masers at NPL. In addition, each service node is provided with a local caesium clock that is continuously steered to UTC(NPL) which can provide up to 30 days holdover in the event of total loss of PTP signal from NPL. 

Does the NPLTime® signal get affected by GNSS jamming or spoofing attempts?  

No. The NPLTime® infrastructure is completely independent of GNSS signals and as such is not susceptible to jamming or spoofing. 

Is NPL monitoring my end point devices?

NPL is monitoring the timing devices at the NPL service nodes as well as the NPLTime Certified® reseller end point devices. Most monitoring for the NPLTime Certified® service is done using SNMP requests, and for this purpose resellers are required to provide read-only SNMP access to their endpoints. It is also expected that resellers will monitor their own equipment and network links and notify NPL of any service-affecting events that may occur on their network. 

Does NPL offer a service certification?   

As part of the NPLTime Certified® service, NPL will calibrate the reseller timing devices against UTC(NPL) and apply the required PTP offset to align it to within 1μs accuracy to UTC(NPL). NPL then issues a certificate which remains valid unless any changes occur on the reseller network which may cause the device offset to change significantly. In that instance, a re-calibration is required. 

Is NPLTime Access® traceable to UTC(NPL)? 

Yes. NPLTime Access® is traceable to UTC(NPL) at the service nodes in Telehouse and Daisy, Reading. It is the responsibility of the user to maintain and prove traceability to UTC(NPL) beyond the service nodes​. 

Is NPLTime® traceable to UTC(NPL) at the reseller timing devices? 

Yes. NPLTime Certified® service is traceable to UTC(NPL) at the end points. Traceability is achieved at the calibration phase of the devices and maintained because of the monitoring of the link by NPL. Traceability is guaranteed with the issuing of a service certificate by NPL. 

In which locations is the 1μs to UTC(NPL) accuracy guaranteed? 

The SLA of 1μs accuracy to UTC(NPL) is guaranteed at the reseller timing devices as well as the NPL service nodes. 

NPLTime Certified®: 1μs at the reseller end point 

NPLTime Access®: 1μs at the NPL service nodes 

Is NPLTime® protected by high availability? 

The availability SLA for both the NPLTime Access® and the NPLTime Certified® services is 99.9% at the service nodes and the reseller end point devices, respectively.​

Is roof access required to subscribe to the NPLTime® services? 

No roof access is required. The NPLTime Access® and NPLTime Certified® services are not reliant on GNSS time signals. 

What are the NPL service nodes? 

The NPL service nodes are locations that provide access and traceability to UTC(NPL). In the future, these nodes could provide access to different types of signals and levels of assurance and security. At the moment, the service nodes in Telehouse and Daisy, Reading offer users access to UTC(NPL) over a fibre link. 

What type of connection do I need to access NPLTime Access® from the service nodes? 

Connection to the NPLTime Access® service is normally provisioned as a 1Gbit/s single-mode optical connection, LC connector, however alternative arrangements can be made with prior agreement. 

NPLTime Access®

Providing all UK industry sectors access to a secure resilient timing signal independent of GNSS.

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NPLTime Certified®

An assured service with certification that provides end users in the finance sector with a timing capability that underpins traceable time-stamping, latency monitoring and synchronisation.

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