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The Accuracy of the Clock Synchronization Achieved by TEMPO in Berkeley UNIX 4.3BSD
July 1989 (vol. 15 no. 7)
pp. 847-853

The authors discuss the upper and lower bounds on the accuracy of the time synchronization achieved by the algorithm implemented in TEMPO, the distributed service that synchronizes the clocks of the University of California, Berkeley, UNIX 4.3BSD systems. The accuracy is shown to be a function of the network transmission latency; it depends linearly upon the drift rate of the clocks and the interval between synchronizations. TEMPO keeps the clocks of the VAX computers in a local area network synchronized with an accuracy comparable to the resolution of single-machine clocks. Comparison with other clock synchronization algorithms shows that TEMPO, in an environment with no Byzantine faults, can achieve better synchronization at a lower cost.

[1] "Adjtime System Call,"UNIX Programmer's Manual (Section 2), 4th Berkeley UNIX Distribution Release 3, Feb. 1985.
[2] F. Cristian, H. Aghili, and R. Strong, "Clock synchronization in the presence of omission and performance faults, and processors joins," inProc. 16th Anna. Symp. Fault-Tolerant Computing Systems, Vienna, July 1986, pp. 218-223.
[3] R. Gusella and S. Zatti, "TEMPO-A network time controller for a distributed Berkeley UNIX system."IEEE Distributed Processing Tech. Comm. Newslett., vol. 6, no. S1-2, pp. 7-15, June 1984.
[4] R. Gusella and S. Zatti, "The Berkeley UNIX 4.3BSD time synchronization protocol specification," Univ. California, Berkeley, Rep. UCB/CSD 85/250, June 1985.
[5] R. Gusella and S. Zatti, "An election algorithm for a distributed clock synchronization program," inProc. IEEE 6th Int. Conf. Distributed Computing Systems, Boston, MA, May 1986. pp. 364-371.
[6] J.Y. Halpern et al., "Fault-Tolerant Clock Synchronization,"Proc. Third Ann. ACM Symp. Principles of Distributed Computing, ACM, New York, 1984, pp. 89-102.
[7] L. Lamport and P. Melliar-Smith, "Byzantine clock synchronization," inACM 3rd PODC Conf. Proc., 1984, PP. 10-16.
[8] L. Lamport and P.M. Melliar-Smith, "Synchronizing Clocks in the Presence of Faults,"J. ACM, Vol. 32, No. 1, Jan. 1985, pp. 52-78.
[9] B. Lampson, "Hints for computer system design." inProc. 9th SOSP. Operating System Review, ACM, vol. 17, Oct. 1983, pp. 33-48.
[10] J. Lundelius and N. Lynch, "A new fault-tolerant algorithm for clock synchronization," inProc. Principles Distributed. Comput., June 1984, pp. 75-88.
[11] J. Postel, Ed., "Internet control message protocol--DARPA Internet program protocol specification," USC/Inform. Sci. Inst., Rep. RFC 792, Sept. 1981.
[12] T.K. Srikanth and S. Toueg, "Optimal Clock Synchronization,"J. ACM, Vol. 34, No. 3, July 1987, pp. 626-645.

Index Terms:
upper bounds; clock synchronization; TEMPO; Berkeley UNIX 4.3BSD; lower bounds; distributed service; network transmission latency; VAX computers; local area network; fault tolerant computing; local area networks; synchronisation; Unix
R. Gusella, S. Zatti, "The Accuracy of the Clock Synchronization Achieved by TEMPO in Berkeley UNIX 4.3BSD," IEEE Transactions on Software Engineering, vol. 15, no. 7, pp. 847-853, July 1989, doi:10.1109/32.29484
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