Subject: [ipfix-info] draft-ietf-ipfix-info-01 issue: 32-bit timestamp type

From: Simon Leinen <[email-masked]>
Date: Wed, 27 Aug 2003 22:04:55 +0200

The current -ipfix-info- draft specifies three types to represent
"specific instant[s] of time", namely dateTime, ipdr:dateTimeMsec, and
ipdr:dateTimeUsec, with second, millisecond, and microsecond
resolution, respectively.  DateTime can be represented in 32 bits, the
other two in 64 bits each.

I don't see a pressing need to have "dateTime".  It is nice to have a
timestamp type that can fit into 32 bits, but the resolution will be
insufficient for many applications.  If we want such a compact
timestamp type, I'd propose to define one that has better resolution,
at the cost of a smaller range: 32 bits can accomodate 136 years at
1-second resolution, almost 50 days at millisecond resolution, or 1
hour 19 minutes at microsecond resolution.  The last combination would
be perfectly adequate for commonly flow timeouts today.

Suggested text changes:

4.14 (dateTime) should be replaced with

    4.14 timeStampUsec

    The "timeStampUsec" type represents a specific instant of time.
    It is further restricted from the basic XML dateTime type to
    having a precision of microseconds.

    It is represented as the number of microseconds between 0:00:00 on
    January 1, 1970 (UTC) and the time in question, modulo 2^32.

    Note that timestamps of this type can only be unambiguously
    interpreted in a context where the range of feasible times is
    limited to 4294.9673 seconds or around 1 hour 19 minutes.
-- 
Simon.

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