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Re: High level comment on draft-li-ccamp-confirm-data-channel-status-00.txt,

Hi all,
The problem statement in this draft is clear, and it seems to me that this problem might arise in a real network depending on the way the network is managed.
It is also clear to me that the current signaling protocols handle this type of problem , but that the process is not ideal. That is, LSPs would not necessarily fail to set up, but there might be some exchange of PathErr messages with Acceptable Label Set objects. Since the problem described in the draft is likely to be persistent, this signaling exchange would possibly be required on every LSP setup that uses the link in question. Functional, but not ideal.
It would be good if you could add a short sub-section to section 2 to describe how the existing signaling protocols will handle the problem and why you believe that this is not adequate.
Now, in general, we don't develop protocol extensions to optimise for error cases, so we have to be careful. If your proposals required continuous monitoring of available resources on each link, that would be a step to far. But if your proposal reflects a start-of-day cross-check followed (optionally) by updates triggered by operator intervention or infrequent timers, that is likely to be acceptable.
With regard to the use of existing messages or the definition of new messages: there are architectural and implementation choices. Although we inevitably need to be driven by the implementations, I am not a fan of overloading messages. IMHO the Fault Management messages are currently triggered by a perceived fault: they are used to report and isolated faults. The new function is used to detect faults, not to report or isolate them.
While I can see Diego's point that the objective is to find faults, the messages proposed by Dan do not report faults, they report information. Faults are only detected when the correlation between information at the two ends of the link is made. I think that if you wanted to go down the route suggested by Diego you would probably want to limit the information exchanged to only the data channels that are suspect, but I don't see how you can report the channels that are not available (because you might not know about them!) - it is only by hearing about the channels that your partner believes exist that you can deduce problems.
In terms of implementation, it really doesn't seem to be very expensive either way. You might want to consider how backward compatibility works with the two options. It is pretty clear how to handle a new message type that is not supported. What will be the impact of adding new TLVs to existing messages? 

Cheers,
Adrian
----- Original Message ----- From: "Diego Caviglia" <Diego.Caviglia@marconi.com> 
To: "Dan Li <danli" <danli@huawei.com>
Cc: "xuhuiying" <xuhuiying@huawei.com>; "Zafar Ali (zali) <zali" <zali@cisco.com>; "MEURIC Julien RD-CORE-LAN <julien.meuric" <julien.meuric@orange-ft.com>; "ccamp <ccamp" <ccamp@ops.ietf.org> 
Sent: Wednesday, August 23, 2006 10:31 AM
Subject: Re: High level comment on draft-li-ccamp-confirm-data-channel-status-00.txt, 




Hi Dan,
       first of all I think that the ID addresses a real problem.
Regarding the bits and bytes I prefer to not implemet new messages but just 
updateds the existing ones that seems to fit to the problem.

I think that having a timeslot that should be usable that is actually
unusable is a failure from the control plane prespective.

So I think that is correct to use the Fault Management Messages to convey
information about unusable channles.

Regards

Diego



Dan Li <danli@huawei.com>@ops.ietf.org on 23/08/2006 09.55.49

Sent by:    owner-ccamp@ops.ietf.org


To:    xuhuiying@huawei.com, "Zafar Ali (zali)" <zali@cisco.com>, MEURIC
      Julien RD-CORE-LAN <julien.meuric@orange-ft.com>
cc:    ccamp <ccamp@ops.ietf.org>

Subject:    Re: High level comment on
      draft-li-ccamp-confirm-data-channel-status-00.txt,

Hi,

Thanks Julien and Zafar for your comments. I agree with Julien. This I-D
just wants to provide a control plane tool to detect the inconsistent data
channel status in the tranport plane.

Actually I have received several private emails think this I-D addresses a
real problem, but regarding the new LMP messages which are introduced in
this I-D, some people pointed out that the already deployed channelstatus
messages (id = 17, 18, 19 and 20) may be extended to carry also the
timeslot information instead only data link. But I have a concern that the
Fault Management Messages usually are triggered by fault detection, these
messages should not be sent if no fault is detected. The confirmation of
data channel status may need to be performed periodically or triggerd by
user.

I would like to hear from you guys, what's your comments? Not only the
concerns raised above, but also other issues in this I-D.

Regards,

Dan

----- Original Message -----
From: "MEURIC Julien RD-CORE-LAN" <julien.meuric@orange-ft.com>
To: "Zafar Ali (zali)" <zali@cisco.com>; <xuhuiying@huawei.com>;
<danli@huawei.com>
Cc: "ccamp" <ccamp@ops.ietf.org>
Sent: Tuesday, July 11, 2006 2:31 AM
Subject: RE: High level comment on
draft-li-ccamp-confirm-data-channel-status-00.txt,


Hi Zafar.

I don't really get you on this. I figure out you're referring to
removing the connection states when RSVP refreshes are not received any
more, aren't you? If so, I'm afraid this is not enough for transmission
devices, where resources can be physically cross-connected even though
there is no (or no longer) corresponding RSVP state. Therefore having a
mechanism to avoid such discrepancies would be welcome.

Regards,

Julien


P.S.: If you totally rely on a management plane, I agree this should be
useless (e.g. the NMS should already know if a cross-connection deletion
failed, cf. Diego's 2nd slides seen this morning).

________________________________


From: owner-ccamp@ops.ietf.org [mailto:owner-ccamp@ops.ietf.org] On
Behalf Of Zafar Ali (zali)

Dear Authors,

RSVP refreshes do this job, so I am not sure motivation for this draft/
LMP extensions.

n.b. The draft state, "Although such a situation can be resolved through
the use of the Acceptable Label Set object in GMPLS signaling [RFC3473],
such a procedure is inefficient since it may require an additional
signaling exchange for each LSP that is set up", so I assume that RSVP
signaling is present (Although I did not understand the quoted statement
from the ID). Even if RSVP is not present, e.g., optical core is
completely controlled by a management entity, I would argue introduce
presence of LMP.

Thanks

Regards... Zafar