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