From: "Hernandez-Valencia, Enrique (Enrique)" <enrique@alcatel-lucent.com>
To: Adrian Farrel <adrian@olddog.co.uk>; Giovanni Martinelli <giomarti@cisco.com>; Malcolm Betts <betts01@nortel.com>; "O'Connor, Don" <don.oconnor@us.fujitsu.com>
Cc: ccamp@ops.ietf.org
Sent: Tuesday, March 10, 2009 1:31:33 PM
Subject: RE: Measuring impairments [Was: Updated Draft Liaiosn to Q6/15]
Adrian,
If one replaces "optical impairments" for "packet impairments" (e.g.,
excessive BER, excessive PLR, excessive delay/delay variation) and
compares that with what CCAMP currently does for PSC technologies, would
that help clarify what CCAMP wants to do for WSON?
It would seem the focus of the CCAMP protocol extension would be on
advertising budgets/objectives not on actual impairment measurements.
Regards,
Enrique
-----Original Message-----
From:
owner-ccamp@ops.ietf.org [mailto:
owner-ccamp@ops.ietf.org] On
Behalf Of Adrian Farrel
Sent: Tuesday, March 10, 2009 12:48 PM
To: Giovanni Martinelli; Malcolm Betts; O'Connor, Don
Cc:
ccamp@ops.ietf.orgSubject: Measuring impairments [Was: Updated Draft Liaiosn to Q6/15]
I'm going to try to answer all of the comments about measuring
impairments
in one email.
I'm arguing all of this from an abstract point of view. I want to "out"
in
advance of the meeting as much of opinion held in CCAMP. I do not
believe it
is valuable to go into the meeting expressing what we think may be Q6's
view. Instead, we need to say what it is people in CCAMP may want to do.
Then we can get Q6 feedback on whether that is practical and what the
concerns are.
So...
The ability to measure optical impairments on an active path is claimed
by
several vendors. I am not in a position to judge whether they are
successful
or not.
Giovanni reasonably asks "what exactly you mean by *ability to
measure*?"
We are proposing protocol
extensions that allow nodes to distribute
information about optical impairments. It is not our business to define
from
where this information is gathered. We can observe that the information
might be configured, might be measured during network provisioning and
held
static, might be determined by a node applying some algorithm to
configured
on pre-measured information, or might be measured dynamically. So we can
choose between:
- optical impairments can be advertised, but cannot be updated
- optical impairments can be advertised, and can be updated
If we choose the first of these, it seems that we are shutting out what
some
people want to be able to do. If we choose the latter, we are not
requiring
anyone to update the information they advertise, but we are allowing
this to
be done if a node chooses to do so.
To answer Don specifically, I see no proposal in CCAMP about which
impairments could be measured or how they would be measured. But, to
turn
this point around, I do not believe that CCAMP should say "you must not
measure an impairment". As Don says, this is outside our remit.
Malcolm's suggestion doesn't cut it for me.
By saying "We understand that Q6 currently has no requirement to measure
impairments after the transport equipment is deployed" we miss the
point.
The point is not what Q6 requires or does not require, but is what CCAMP
requires.
So I wonder what is wrong with the statement (in the context of
describing
what CCAMP wants to do) that "There is no requirement to measure
impairments."
Don objected specifically to...
> However, if an implementer chooses to measure impairments
> on their device, this should not be prohibited, and should be
> accommodated.
How would it be if we
defered the practicality of such measurements to
the
ITU? We could then write...
However, if an implementer chooses to measure impairments
on their device, and this can be achieved within the mechanisms
and definitions defined by the ITU-T, then this should not be
prohibited by the CCAMP protocol mechanisms, and should be
accommodated within GMPLS.
Cheers,
Adrian