RE: [EFM]Event Time Stamp
Kevin,
As I noted in my original email, there seem to be a disagreement between
Clause 57 with 30.11.1.1.37-40.
For example, 57.5.3.1 explicitly states that the time stamp is 16-bit:
"Event Time Stamp. This two-octet field indicates the time reference when
the event was generated, in terms of 100ms intervals, encoded as a 16-bit
unsigned integer. When received from the remote DTE and if Clause 30 is
present, this maps to 30.11.1.1.37."
Then section 30.11.1.1.37 (which defines aOamRemoteErrSymPeriodEvent) has
this text:
"A SEQUENCE of four instances of the type INTEGER... The first INTEGER
represents the Event Time Stamp field..."
I would appreciate it if you would explain this further. Also, could you
refer me to the right source for this INTEGER encoding with field width you
mentioned?
Thank you very much.
Regards,
Yonghong Ren
Appian Communications.
-----Original Message-----
From: Kevin Daines [mailto:Kevin.Daines@worldwidepackets.com]
Sent: Thursday, August 14, 2003 4:48 PM
To: Yonghong Ren; Matt Squire; stds-802-3-efm@ieee.org
Subject: RE: [EFM]Event Time Stamp
The attributes found in 30.11 contain integers of various lengths, from
two-octets up to eight-octets. The referenced attributes found in
30.11.1.1.37-40 define integers corresponding to fields defined in Clause
57. The integers are sized according to the field widths.
Kevin Daines
Editor, EFM OAM
-----Original Message-----
From: Yonghong Ren [mailto:ren@appiancom.com]
Sent: Wednesday, August 06, 2003 11:53 AM
To: 'Matt Squire'; Yonghong Ren; stds-802-3-efm@ieee.org
Subject: RE: [EFM]Event Time Stamp
Thanks for the explanation!
So this time stamp gives the more or less precise timing of events that are
clumped together. If events are spaced more than 109 (65535/10/60) minutes
apart, they became meaningless. One would imagine this "micro" view needs to
be supplemented by the "macro" view of local time stamping as events are
received.
Perhaps a few sentences to explain this in the standard would be useful?
Thanks again.
-- Yonghong Ren
-----Original Message-----
From: Matt Squire [mailto:MSquire@HatterasNetworks.com]
Sent: Tuesday, August 05, 2003 10:07 PM
To: Yonghong Ren; stds-802-3-efm@ieee.org
Subject: Re: [EFM]Event Time Stamp
Here's my recollection of the justification of timestamping...
The timestamp is not intended to represent the time since system uptime. At
least not for any piece of reliable equipment:) It was added to provide
"relative" times between events for more accuracat reporting (e.g. if source
timestamps X & Y as happening 500 ms apart, thats probably more accurate
than the receiver getting them 650ms apart due to the delay caused by the
limited number of OAM frames). The origin of the utility can be found in
http://www.ieee802.org/3/efm/public/mar03/oam/gerhardt_oam_1_0303.pdf.
- Matt
On Mon, 4 Aug 2003 16:38:59 -0400, Yonghong Ren <ren@appiancom.com> wrote:
> The most recent draft (2D) defines the Event Time Stamp in Event TLV as
> 16-bit, in the unit of 100ms. If we assume this "time reference" to mean
> something like a system uptime, then it's simply not wide enough.
> Interestingly, the Event Time Stamp references section 30.11.1.1.37-40,
> where the time stamps seem to be defined as 32-bit integers. So, perhaps
> it's simply a typographical error?
> I would appreciate any clarification for me. Thanks.
> -- Yonghong Ren
>