Hello,
I filled in table 8 and added some text to section 3.8 of
draft-rodrigues-lindqvist-tictoc-req-02.txt
Vladimir
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Vladimir Smotlacha CESNET z.s.p.o
E-Mail: [email protected] Zikova 4
Phone: +420 2 24352915 160 00 Prague 6
Fax: +420 2 24313211 Czech Republic
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This document contains edited chapter 3.8 of TICTOC Requirement
draft-rodrigues-lindqvist-tictoc-req-02.txt
3.8. Metrology
Metrology for time and frequency is today mostly using tailored
equipment and cabling for time/frequency transfer when doing
laboratory work. However, in the future, using IP over existing
networks in the laboratories would allow for greater flexibility and
reuse of existing infrastructure rather than building out more
special purpose infrastructure.
3.8.1. Metrology Requirements
We should distinguish between "primary" metrology of time and frequency
performed in national metrology laboratories and some other timing
centers (which deals with highly accurate and stable frequency standards,
typically cesium standards and hydrogen masers and which ensures
synchronization with a nanosecond accuracy) and applied metrology that
mainly calibrates oscillators and clocks used as "secondary" standards in
research organizations and industry. The use of time and frequency
transfer in packet networks is limited in "primary" metrology, as it
operates with frequency accuracy and stability in the order of 1e-14 and
better and time accuracy in nanoseconds (1 ns represents 1 foot of the
light path in vacuum). In turn, time and frequency transfer through
packet networks is quite challenging for applied metrology - it can
profit from any improvement of transfer accuracy, therefore the values in
table 8 should be considered as minimum target values. Whenever
possible, accuracy of distributed time should be better then time
accuracy provided by a GPS receiver. Short distance application (over
LAN) usually require better accuracy than long distance application using
WAN.
Note: some applications might belong into both metrology and
measurement application groups.
The requirements for the Metrology is summarized in the table 8.
Metrology Requirements
+-----------------------------+-----------------------------+
| Requirements | Metrology |
+-----------------------------+-----------------------------+
| Synchronization type (e.g. | Time and frequency |
| time, frequency or phase) | |
| --------------------------- | --------------------------- |
| Frequency stability | 1 ppb, lowest possible |
| | phase noise |
| --------------------------- | --------------------------- |
| Frequency accuracy | 1 ppb |
| --------------------------- | --------------------------- |
| Uncalibrated time/time | Lowest possible phase noise |
| stability | |
| --------------------------- | --------------------------- |
| Uncalibrated time/time | 1 us |
| accuracy | |
| --------------------------- | --------------------------- |
| Stabilization time | Not important, 1 hour is |
| | acceptable |
| --------------------------- | --------------------------- |
| Jitter on recovered timing | 1 us |
| signal | |
| --------------------------- | --------------------------- |
| Wander on recovered timing | 1 us |
| signal | |
| --------------------------- | --------------------------- |
| What expected network | Any that can offer |
| characteristics (WAN, LAN, | required parameters |
| MAN, private, public, etc)? | |
| --------------------------- | --------------------------- |
| Does the application | Authentication is required |
| requires security? (if so, | when public networks |
| which one: authentication, | are used |
| encryption,traceability, | |
| others) | |
| --------------------------- | --------------------------- |
| Reliability requirements | Low fault tolerance, user |
| (e.g. fault tolerance) | should know whether expected|
| | parameters were assured |
| | or not |
| --------------------------- | --------------------------- |
| Traceability to a specific | Very important |
| clock, clock quality, path, | |
| time | |
| --------------------------- | --------------------------- |
| Holdover requirement | |
| --------------------------- | --------------------------- |
| Cost (consumer, enterprise, | Cost should correspond |
| carrier) | with provided pamaters |
| --------------------------- | --------------------------- |
| Auto-configuration (plug | Important at client side |
| and play) | |
| --------------------------- | --------------------------- |
| Manageability (how much | Both provider and customer |
| effort the operator needs | should accept network |
| to put in to manage this | related configuration, |
| application?) - In-band or | long distribution path |
| out-of-band of protocol | might require calibration |
| (MIBs?) | |
| --------------------------- | --------------------------- |
| Scale and scalability | Scalability is not |
| | important, only a few |
| | transfers will be active |
| | from one source at the same |
| | time |
+-----------------------------+-----------------------------+
Table 8
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