Below the Sky: Presentations#

Chairs: Raimena Veisllari (Sikt), Domenico (Dom) Vicinanza (GÉANT), Guy Roberts (GÉANT); talks from GÉANT, RENATER, and Sikt/Nordic partners

• Why: The engineering follow-through to the CESNET talk — a BoF on building terrestrial, GNSS-independent time networks across Europe, grounded in the GÉANT C-TFN Incubator report (Zenodo).
• What: Substantiated results, not just a roadmap: a 498 km Prague–Vienna field-installed loop using five bidirectional amplifiers achieved ±100 ps time-transfer stability — well inside the 1 ns target — with 1 Gbps WR signals sharing fiber with 400G coherent channels at no measurable BER impact given a suitable guard-band. The report compares three regeneration architectures with performance data and an interactive cost calculator: 1R bidirectional amps (best timing, fixed wavelength per span), 2R OEO (good cost-performance trade-off), 3R WR switches (full flexibility, more jitter in cascade). Plus spectrum planning guidance (L-band is amplifiable but typically unused for data — an attractive WR home; placing WR at the C-band edge halves guard-band cost) and operational design requirements (dual PSUs, SNMP traps, OSC channel, support model) — including the candid gap that SNMP management of open-source WR switches is still being defined by the consortium.
• How: White Rabbit over long-haul DWDM with careful calibration (any Tx/Rx asymmetry measured and compensated, recalibration after every fiber repair); roundtables organized by deployment challenge (optical layer vs. economics/OAM).
• Where applicable: European NREN context and DWDM-platform-dependent (built-in L-band filters help), but the whitepaper's comparison data and cost model are directly consumable by any operator considering sovereign terrestrial time.