Technical Standard DCE 1.1: Time Services NICAL H S C T A E N T D A R D [This page intentionally left blank] X/Open CAE Specification X/Open DCE: Time Services X/Open Company Ltd. October 1994, X/Open Company Limited All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owners. Published by X/Open Company Limited under license from the Open Software Foundation (OSF). Portions of this document include text excerpted and/or derived from the Open Software Foundation Application Environment Specification for Distributed Computing (AES/DC) with the permission of OSF. However, the text appearing herein does not represent the official OSF version of the AES/DC, which is copyright 1992, 1993 Open Software Foundation, Inc. This document and the software to which it relates are derived in part from materials which are copyright 1990, 1991 Digital Equipment Corporation and copyright 1990, 1991 Hewlett-Packard Company. X/Open CAE Specification X/Open DCE: Time Services ISBN: 1-85912-067-9 X/Open Document Number: C310 Published by X/Open Company Ltd., U.K. Any comments relating to the material contained in this document may be submitted to X/Open at: X/Open Company Limited Apex Plaza Forbury Road Reading Berkshire, RG1 1AX United Kingdom or by Electronic Mail to: [email protected] ii X/Open CAE Specification (1994) Contents Part 1 Time Services and Protocols ...................................................... 1 Chapter 1 Introduction............................................................................................... 3 1.1 Time in Distributed Systems .................................................................... 3 1.2 Time and Clocks.......................................................................................... 4 1.2.1 Time............................................................................................................ 4 1.2.2 Clocks......................................................................................................... 4 1.2.3 Correct Time ............................................................................................. 5 1.3 Time Service Rationale .............................................................................. 6 1.4 Architectural Overview............................................................................. 7 1.5 Conformance Requirements..................................................................... 8 Chapter 2 Time Service Functional Overview ............................................ 9 2.1 Obtaining a Time Value From a Server .................................................. 9 2.2 Obtaining Time Values from Time Providers....................................... 12 2.3 Computing a Correct Time....................................................................... 13 2.4 Adjusting the Clock.................................................................................... 16 2.5 Determining the Inaccuracy ..................................................................... 17 2.6 Leap Seconds ............................................................................................... 19 2.6.1 Leap Seconds and Inaccuracy ............................................................... 19 2.6.2 Leap Seconds and Obtaining Time ...................................................... 22 2.7 Time Zones................................................................................................... 23 2.8 Local Faults .................................................................................................. 23 2.9 Primitive Procedures.................................................................................. 24 2.9.1 The EstimateServerTime Procedure..................................................... 25 2.9.2 The ComputedTimeMinimum Procedure.......................................... 26 2.9.3 The AdjustClock Procedure................................................................... 28 2.9.4 The AdjustClkEnd Procedure ............................................................... 30 2.9.5 The SetClock Procedure ......................................................................... 31 2.9.6 The CalcInaccuracy Procedure ............................................................. 32 Chapter 3 Time Service Configuration............................................................. 33 3.1 Configuration............................................................................................... 34 3.2 Local Set Import and Export..................................................................... 35 3.3 Global Set Import and Export .................................................................. 36 3.4 Couriers......................................................................................................... 37 Chapter 4 Time Service Clerk Specification ................................................. 39 4.1 Initialising the System Clock.................................................................... 39 4.2 Synchronisation........................................................................................... 40 4.3 Determining the Next Synchronisation ................................................. 42 4.4 Maintaining the Server Lists..................................................................... 43 X/Open DCE: Time Services iii Contents Chapter 5 Time Service Server Specification ............................................... 45 5.1 Initialisation ................................................................................................. 45 5.2 Epochs ........................................................................................................... 46 5.3 Synchronisation........................................................................................... 47 5.3.1 Synchronising with a TP ........................................................................ 47 5.3.2 Synchronising with Other Servers ....................................................... 47 5.4 Determining the Next Synchronisation ................................................. 49 5.5 Checking For Faulty Servers..................................................................... 49 5.6 Maintaining the Server Lists..................................................................... 50 Chapter 6 Time Service IDL Declarations ..................................................... 51 6.1 Data Types and Ranges ............................................................................. 51 6.1.1 The utc Structure...................................................................................... 51 6.1.2 Parameter Ranges .................................................................................... 51 6.2 Local Set Time Service Interface.............................................................. 52 6.2.1 ClerkRequestTime................................................................................... 52 6.2.2 ServerRequestTime ................................................................................. 53 6.3 Global Set Time Service Interface............................................................ 54 6.3.1 ClerkRequestGlobalTime....................................................................... 54 6.3.2 ServerRequestGlobalTime..................................................................... 55 6.4 Time Provider Interface............................................................................. 56 6.4.1 Data Types................................................................................................. 57 6.4.2 ContactProvider....................................................................................... 58 6.4.3 ServerRequestProviderTime.................................................................. 58 Part 2 Time API.................................................................................................... 59 Chapter 7 Time API...................................................................................................... 61 7.1 Timestamps.................................................................................................. 62 7.1.1 The utc_t Type .......................................................................................... 62 7.2 Non-opaque Time Representations ........................................................ 63 7.2.1 Character Representations of Time...................................................... 63 7.2.2 Character-relative Time Type................................................................ 64 7.2.3 The tm Structure ...................................................................................... 65 7.2.4 The timespec Structure........................................................................... 65 7.2.5 The reltimespec Structure ...................................................................... 65 7.2.6 Conversion Rules..................................................................................... 66 7.3 Time Service API Taxonomy .................................................................... 67 7.3.1 Time Conversions.................................................................................... 68 Chapter 8 Time API Manual Pages..................................................................... 71 utc_abstime( ) ..................................................................................................