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Hardware Support for Clock Synchronization in Distributed Systems. Martin Horauer University of Technology Vienna Department of Computer Technology. LANs (hardware). precision, accuracy. NTP. LANs (software). 1ms. LANs (hardware). 1 s. GPS. PLL. 1ns. 10m. 1 km. distance. 100m.
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Hardware Support for Clock Synchronization in Distributed Systems Martin Horauer University of Technology Vienna Department of Computer Technology
LANs (hardware) precision, accuracy NTP LANs (software) 1ms LANs (hardware) 1s GPS PLL 1ns 10m 1 km distance 100m Objectives InternalClock Synchronization: | Cp(t) - Cq(t) | External Clock Synchronization: | Cp(t) - t |
OCXO or XO + Rate Synchronization Hardware Support Clock ASIC UTCSU Requirements • Hardware Clock • small oscillator drift • good stability • fine grained • rate and state adjustable • Access to an external time reference • Timestamp Messages • tight coupling of timestamp mechanisms to the network medium
Software Timestamping Cq(t) - Cp(t) TR – TS - [ - ] = max - min
Timestamping with HardwareSupport Cq(t) - Cp(t) TR – TS - [ - ] = max - min
Transmit TS FCS Transmit TS FCS Transmit Timestamping: Preamble User Data FCS SFD Dest. Addr. Src. Addr. TF = Receive CRC check: FCS User Data Dest. Addr. Src. Addr. TF Transmit TS FCS Receive TS Receive Timestamping: FCS Preamble User Data SFD Dest. Addr. Src. Addr. TF Transmit TS Receive TS FCS Clock Synchronization Packet Timestamping