TY - GEN
T1 - Taming asymmetric network delays for clock synchronization using power grid voltage
AU - Rabadi, Dima
AU - Tan, Rui
AU - Yau, David K.Y.
AU - Viswanathan, Sreejaya
N1 - Publisher Copyright:
© 2017 ACM.
PY - 2017/4/2
Y1 - 2017/4/2
N2 - Many clock synchronization protocols based on message pass- ing, e.g., the Network Time Protocol (NTP), assume sym- metric network delays to estimate the one-way packet trans- mission time as half of the round-trip time. As a result, asymmetric network delays caused by either network con- gestion or malicious packet delays can cause significant syn-chronization errors. This paper exploits sinusoidal voltage signals of an alternating current (ac) power grid to tame the asymmetric network delays for robust and resilient clock synchronization. Our extensive measurements show that the voltage signals at geographically distributed locations in a city are highly synchronized. Leveraging calibrated voltage phases, we develop a new clock synchronization protocol, which we call Grid Time Protocol (GTP), that allows di- rect measurement of one-way packet transmission times be- tween its slave and master nodes, under an analytic condi- tion that can be easily verified in practice. The direct mea- surements render GTP resilient against asymmetric network delays under this condition. A prototype implementation of GTP, based on readily available ac/ac transformers and PC- grade sound cards as voltage signal sampling devices, main- tains sub-ms synchronization accuracy for two nodes 30 km apart, in the presence of malicious packet delays. We believe that GTP is suitable for grid-connected distributed systems that are currently served by NTP but desire higher resilience against network dynamics and packet delay attacks.
AB - Many clock synchronization protocols based on message pass- ing, e.g., the Network Time Protocol (NTP), assume sym- metric network delays to estimate the one-way packet trans- mission time as half of the round-trip time. As a result, asymmetric network delays caused by either network con- gestion or malicious packet delays can cause significant syn-chronization errors. This paper exploits sinusoidal voltage signals of an alternating current (ac) power grid to tame the asymmetric network delays for robust and resilient clock synchronization. Our extensive measurements show that the voltage signals at geographically distributed locations in a city are highly synchronized. Leveraging calibrated voltage phases, we develop a new clock synchronization protocol, which we call Grid Time Protocol (GTP), that allows di- rect measurement of one-way packet transmission times be- tween its slave and master nodes, under an analytic condi- tion that can be easily verified in practice. The direct mea- surements render GTP resilient against asymmetric network delays under this condition. A prototype implementation of GTP, based on readily available ac/ac transformers and PC- grade sound cards as voltage signal sampling devices, main- tains sub-ms synchronization accuracy for two nodes 30 km apart, in the presence of malicious packet delays. We believe that GTP is suitable for grid-connected distributed systems that are currently served by NTP but desire higher resilience against network dynamics and packet delay attacks.
UR - https://www.scopus.com/pages/publications/85022085308
UR - https://www.scopus.com/pages/publications/85022085308#tab=citedBy
U2 - 10.1145/3052973.3053020
DO - 10.1145/3052973.3053020
M3 - Conference contribution
AN - SCOPUS:85022085308
T3 - ASIA CCS 2017 - Proceedings of the 2017 ACM Asia Conference on Computer and Communications Security
SP - 874
EP - 886
BT - ASIA CCS 2017 - Proceedings of the 2017 ACM Asia Conference on Computer and Communications Security
PB - Association for Computing Machinery, Inc
T2 - 2017 ACM Asia Conference on Computer and Communications Security, ASIA CCS 2017
Y2 - 2 April 2017 through 6 April 2017
ER -