Principles
The CESTime network is built as a network parallel to the Internet, i.e. it runs over separate optical channels. At the same time, it is designed so that we provide no services on it other than time protocols.
Unlike the Internet, it is built as a "one-way" network, i.e. the signal propagates in one direction from CESNET's atomic clocks, which are traceable to the Czech national time standard. Because the signal propagates in one direction, the status map shows arrows (indicating the direction of propagation) and dashed interconnecting lines (which are in standby mode).
Optical Network
The optical network contains 13 main nodes, with more nodes in some areas (the Prague metropolitan area and Brno). They are interconnected by 26 links organized into four rings to maintain redundancy. In total, the network spans 3,785 km (the value reported by measurements).
The network has an interconnection to Slovakia and a planned interconnection to Vienna, which are used to compare the time of the national time standards of the respective institutions.
Time Layer
The switches synchronize their time using the White Rabbit protocol (a protocol developed by CERN) based on PTP/IEEE 1588.
Quality Parameters
The network is currently in pilot operation, which provides full services to users, but during which we are verifying the designed processes and the planned values of the network. We are not aware of any network of similar scale in the world, so we consider it necessary to verify all processes and parameters against reality.
Planned Network Parameters (so far confirmed by operation)
Deviation from UTC(TP): ±20 ns
Our reference is not UTC but the national time scale UTC(TP), because our clocks are traceable to it and we neither need nor want to deal with the deviation of UTC(TP) from UTC (you can find it in the Circular T document published by the BIPM: https://www.bipm.org/en/time-ftp/circular-t).
Deviation between nodes / PoPs: ±5 ns
Estimated deviation at the client:
-- WR (with our monitoring): 3 ns relative to the PoP
-- PTP with hardware support along the path: approx. 1 µs