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Browse Prior Art Database

Synchronization of Real Time Clocks

IP.com Disclosure Number: IPCOM000110018D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Roper, MI: AUTHOR [+2]

Abstract

Disclosed is a method which enables two computer systems engaged in a cooperative activity that requires the system to have a common time reference, to establish such a reference to an accuracy within one half of the difference between the inter-machine propagation delays.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 57% of the total text.

Synchronization of Real Time Clocks

       Disclosed is a method which enables two computer systems
engaged in a cooperative activity that requires the system to have a
common time reference, to establish such a reference to an accuracy
within one half of the difference between the inter-machine
propagation delays.

      Existing methods of synchronizing clocks rely on low
propagation delay between the computers, and low processing time on
each computer.  The scheme described below does not rely on these
assumptions, operates over low speed links and eliminates the
processing time delay exhibited by the computers, thereby providing
more accurate synchronization than existing techniques.  The
following references are suggested (1,2).

      Two computer systems may be engaged in a cooperative activity
requiring that both systems have a common time reference.  If the
systems are linked on some form of communications channel with an
unknown and possibly variable time delay, then it is impossible to
exactly synchronize the two clocks.  This is because of the time
taken to propagate any form of synchronization signal from one system
to another.  It is, however, possible to achieve a high degree of
synchronization, even when the systems themselves exhibit unknown and
variable delays in processing the synchronization signal.

      The proposed method for doing this is that one system sends the
other a timestamp (tA), and the receiving system then sets its c...