RFC 956 (rfc956) - Page 1 of 26


Algorithms for synchronizing network clocks



Alternative Format: Original Text Document



Network Working Group                                         D.L. Mills
Request for Comments: 956                               M/A-COM Linkabit
                                                          September 1985

              Algorithms for Synchronizing Network Clocks


Status of this Memo

   This RFC discussed clock synchronization algorithms for the
   ARPA-Internet community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Table of Contents

   1.      Introduction
   2.      Majority-Subset Algorithms
   3.      Clustering Algorithms
   4.      Application to Time-Synchronization Data
   5.      Summary and Conclusions
   6.      References
   Appendix
   A.      Experimental Determination of Internet Host Clock Accuracies
   A1.     UDP Time Protocol Experiment
   A2.     ICMP Timestamp Message Experiment
   A3.     Comparison of UDP and ICMP Time

List of Tables

   Table 1.  C(n,k) for n from 2 to 20
   Table 2.  Majority Subsets for n = 3,4,5
   Table 3.  Clustering Algorithm using UDP Time Protocol Data
   Table 4.  Clustering Algorithm using ICMP Timestamp Data
   Table 5.  ISI-MCON-GW Majority-Subset Algorithm
   Table 6.  ISI-MCON-GW Clustering Algorithm
   Table 7.  LL-GW (a) Majority-Subset Algorithm
   Table 8.  LL-GW (a) Clustering Algorithm
   Table 9.  LL-GW (b) Majority-Subset Algorithm
   Table 10. LL-GW (b) Clustering Algorithm
   Table A1. UDP Host Clock Offsets for Various Internet Hosts
   Table A2. UDP Offset Distribution