Juergen Schoenwaelder Internet-Draft TU Braunschweig Expires May 1999 18 November 1998 DateAndTime Extension for the MIB-2 system Group Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress.'' To view the entire list of current Internet-Drafts, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). Distribution of this document is unlimited. Please send comments to the SNMP Version 3 Working Group, . Abstract This memo defines an extension of the Management Information Base (MIB) for Version 2 of the Simple Network Management Protocol (SNMPv2) as published in RFC 1907. In particular, it defines an object which allows to read and modify the notion of wall clock time accessible by an SNMP agent. The addition of this object allows to use the DateAndTime textual convention as defined in RFC 1903 even on devices that do not have a real-time clock. J. Schoenwaelder [Page 1] Internet-Draft System MIB Extensions November 1998 Table of Contents 1 Introduction ................................................. 2 2 Problem ...................................................... 2 3 Solution ..................................................... 3 4 Definitions .................................................. 4 5 Acknowledgments .............................................. 4 6 Authors' Address ............................................. 5 1. Introduction This memo defines an extension of the Management Information Base (MIB) for Version 2 of the Simple Network Management Protocol (SNMPv2) as published in RFC 1907. In particular, it defines an object which allows to read and modify the notion of wall clock time accessible by an SNMP agent. The addition of this object allows to use the DateAndTime textual convention as defined in RFC 1903 even on devices that do not have a real-time clock. 2. Problem Many MIBs require to time-stamp events. This is usually accomplished by using either the TimeStamp or the DateAndTime textual convention defined in RFC 1903. Both approaches have strength and weaknesses: TimeStamp: + One advantage of a TimeStamp is that sysUpTime is always locally available, even on devices that have no notion of wall clock time. + Further, sysUpTime is supported by the AgentX sub-agent protocol defined in RFC 2257 since it is exchanged in master/sub-agent message exchanges. - A TimeStamp time-stamp is based on sysUpTime and becomes ambiguous after some time. - A TimeStamp has itself no meaning - a manager must also retrieve the current value of sysUpTime and do calculations against its local notion of date and time in order to calculate when an event happened. J. Schoenwaelder [Page 2] Internet-Draft System MIB Extensions November 1998 - A TimeStamp can not be used to time-stamp events that have occurred prior to the initialization of the network management of the system was last re-initialized. - TimeStamps reported by sub-agents can be ambiguous if the master agent has been restarted. Resetting or recalculating time stamps on such an event can be expensive. DateAndTime: + DateAndTime time-stamps report the time an event occurred in the local notion of date and time. A DateAndTime time-stamp is therefore self-contained. + DateAndTime time-stamps are globally unambiguous if they contain the offset from UTC. DateAndTime time-stamps are still locally unambiguous if they miss the offset from UTC. + DateAndTime time-stamps can describe events that have occurred prior to the initialization of the network management subsystem. + DateAndTime time-stamps do not require any special attention in a sub-agent environment when the master agent restarts. - A DateAndTime time-stamp is slightly longer than a TimeStamp time-stamp. - DateAndTime time-stamps requires that the agent has a notion of wall clock time. This is generally not supported on devices without a battery powered clock or devices that do not support time protocols such as NTP. A MIB which records a time-stamp as a DateAndTime value can thus not me implemented on such a device. - The AgentX sub-agent protocol does not allow to share the notion of DateAndTime between sub-agents. The notion of DateAndTime must therefore be exchanged with other local mechanisms. (This is typically a service of the underlying operating system). 3. Solution The sysDateAndTime object defined below solves the main problem with DateAndTime time-stamps by providing a mechanism which allows to configure the date and time with an SNMP set operations. This enables devices without a battery powered clock and without time protocols to have a notion of wall clock time. J. Schoenwaelder [Page 3] Internet-Draft System MIB Extensions November 1998 In addition, the sysDateAndTime object allows a manager to read the remote notion of the current date and time in order to detect clock screw or mis-configurations. This can be of great help when interpreting DateAndTime time-stamp values from devices that have mis-configured clocks. Objects that record a time-stamp can now be written similar to the following example: smRunStartTime OBJECT-TYPE SYNTAX DateAndTime MAX-ACCESS read-only STATUS current DESCRIPTION "The date and time when the execution started. The value '0000000000000000'H is returned if the script has not started yet or if the current date and time is not (yet) known by the agent." DEFVAL { '0000000000000000'H } ::= { smRunEntry 3 } 4. Definitions SNMPv2-MIB-EXT-01 DEFINITIONS ::= BEGIN IMPORTS MODULE-IDENTITY, OBJECT-TYPE, FROM SNMPv2-SMI system FROM SNMPv2-MIB; -- This module is not valid SMIv2. The author left out all the -- administrative stuff in order to keep it small. sysDateAndTime OBJECT-TYPE SYNTAX DateAndTime MAX-ACCESS read-write STATUS current DESCRIPTION "The locally known date and time. The value '0000000000000000'H is returned on systems without a local clock until the local date and time is learned, either from a network time protocol such as NTP or a management set operations on this object." ::= { system 9 } END J. Schoenwaelder [Page 4] Internet-Draft System MIB Extensions November 1998 5. Acknowledgments The definition of the sysDateAndTime object was inspired by a remark Eamonn McManus about implementing DateAndTime objects of the Script MIB in an embedded system without a hardware clock. The comparison of the advantages and disadvantages of the frequently used TimeStamp mechanisms was inspired by discussions about the TimeStamp textual convention in the SMI design team and on the SNMPv3 mailing list. 6. Authors' Address Juergen Schoenwaelder Email: schoenw@ibr.cs.tu-bs.de TU Braunschweig Tel: +49 531 391-3283 Bueltenweg 74/75 38106 Braunschweig Germany J. Schoenwaelder [Page 5]