Re: [nm-wg] standard timestamp format

[Dan Gunter <dkgunter@lbl.gov>]

Good point! Where were you 3 years ago :)

To make sure I understand exactly what you mean, I could revise my 
earlier list of timestamp formats like this:

1. Global timestamps
  (a) NTP seconds
  (b) ISO8601 YYYY-MM-DDThh:mm:ss.ff..fZ
2. Single-source timestamps
  (a) 64-bit counter (?)

Then you are suggesting that a #2 timestamp could be optionally included 
wherever we allow a #1 timestamp.

Don't know about everybody else, but this seems very reasonable to me.

-Dan

Adrian Cockcroft wrote:
> There are two distinct uses for timestamps, which have  
> different/conflicting solutions.
>
> a) universal time to allow correlation of events, especially  
> correlation between endpoints of a link
> If a network goes down, you may get an event from each end of the link,  
> and it needs to be synchronized
> well enough to resolve this as one failure rather than a series of  
> failures.
>
> b) linearly and monotonically increasing time to allow accurate  
> summarization of data from a single
> source, i.e. differencing of timestamps to obtain rates and response  
> times.
>
> An operating system such as Solaris uses two separate timing sources, a  
> global universal time that
> can be synchronized by NTP and set by the user. It can speed up, slow  
> down and make forward and backward
> large jumps. A second "hi-resolution" timer runs off the CPU/System  
> clock crystal and is monotonic and
> linear with better than microsecond resolution. This is used by all the  
> performance metrics, for calculating
> disk service time and CPU microstate accounting. See gethrtime(3C).
>
> The discussion here is centered on the global/universal time format,  
> but if it is to be used to do differencing
> within a system, then it may be worth embedding a local hires timestamp  
> in the format as well, which is only
> valid when differencing times from the same source.
>
> Adrian
>
> On Jun 14, 2004, at 1:55 PM, Dan Gunter wrote:
>
> > I'm not sure that a _single_ standard timestamp format is required;  
> > what I would like to see is a minimal set of timestamp formats that  
> > will satisfy everyone, with rules for converting between them  
> > explicitly documented somewhere. I'm not sure *GGF* is the right 
> > place  for this, ultimately, but I don't see any harm in proposing 
> > something  in this context even if it just ends up becoming input into 
> > another  standards body down the line.
> >
> > I don't want to sidetrack NM-WG, but given that we need to exchange  
> > timestamps and we've already had discussions on this, it looks like  
> > we're already sidetracked, and waiting for another WG to form and  
> > finish just to document this would be a real bump in the road. Not  
> > documenting what decisions we make seems like a waste of a 
> > potentially  more broadly useful set of discussions and decisions.
> >
> > Therefore, I would propose that a few people interested in this get  
> > together enough spare time to write a short-and-sweet document about  
> > the timestamp formats we can agree on. AFAIK, these are currently:
> >
> > - NTP seconds (16 bytes, encoded either "raw", or for XML as hex or  
> > decimal numbers)
> > - ISO8601 (restricted to YYYY-MM-DDThh:mm:ss.ff..fZ variation)
> >
> > [ Note: I would propose that accuracy and resolution representation 
> > be  treated as optional extensions to be specified at some later date. 
> > As  much as I'd like to include these in any documentation we 
> > produce,  they tend to be controversial, and specifying these in a 
> > standard way  is not crucial to moving forward. ]
> >
> > Once this document is done, it could be reviewed by the group as a  
> > whole and, if found satisfactory, thrown into the abyss of GGF  
> > document approval. Whether or not final approval is given, our Web  
> > Services will have some concrete, documented, agreement to go on for  
> > the timestamp at least.
> >
> > The documents cited below could provide background material, but I  
> > think what we need is much simpler, smaller, and easier to agree on.
> >
> > -Dan
> >
> > Brian Tierney wrote:
> >
> > > Hi all:
> > > Richard mentioned that the issue of a standard timestamp has come up  
> > > in  Mark/Paul's implementation work.
> > > There were a couple of documents on this a few years ago:
> > > http://www-didc.lbl.gov/GGF-PERF/GMA-WG/papers/GWD-GP-10-1.pdf
> > > and
> > > http://www.cs.tcd.ie/coghlan/meta/datagrid/PDPTAv7_2.pdf
> > > I asked Steve Tueke what the WS-RF solution to timestamps is, and 
> > > he   said that they have not yet found a critical need for a 
> > > standard   timestamp.
> > > Im not sure of the NM-WG is the right place for this, but I'd like 
> > > to   see the above document
> > > standardized. Other thoughts on this?
> > > ---------------------------------------------------------------------- 
> > > -- -------------------
> > >   Brian L. Tierney,   Lawrence Berkeley National Laboratory (LBNL)
> > >   1 Cyclotron Rd.  MS: 50B-2239,  Berkeley, CA  94720
> > >   tel: 510-486-7381    fax: 510-495-2998   efax:  240-332-4065
> > >   bltierney@lbl.gov   http://www-didc.lbl.gov/~tierney
> > > ---------------------------------------------------------------------- 
> > > -- ------------------