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Hi again:
Carmine Daloia wrote:
Sudheer,
I am not assuming inband communication is supported between the cross-connect
and the line system. That is why I said that when the PXC and line system
are from different vendors such OAM signals would have to be carried over
a separate channel (e.g., LMP-WDM control channel). However, I don't see
why such signals would have to be carried over an LMP control channel between
cross-connects. Also, my point about performance was that we would have
to see if the LMP control channel would meet the performance requirements
for such OAM signals. It very well might. If not, a bit-oriented signaling
interface may be needed between the PXC and the line system.
Ok Let us address the issues separately...
1. Communication between Line System and Cross connect
Defining a bit-oriented (physical) interface and protocol is not really
the task (in my opinion)
of IETF. I am not sure if are creating a problem to solve with the
alarm suppression.
Let me explain...
Let us assume we can correlate and suppress the alarms between the Line
systems
and corss connects. Then we donot need an elaborate bit-oriented protocol.
This
has an assumption that we are talking about not hundereds of failures
but a couple of
failures (for example fiber cuts).
2. Communication between cross connects
THis is needed to localize a fault which in turn can be used as a trigger
for local
restoration.
- sudheer
Thanks
Carmine
Sudheer Dharanikota wrote:
3BFBC412.E5FC940B@nayna.com">Carmine...
Again can you suggest a way to communicate such signals
between line systems and cross connects when inband
communication is not supported between these two systems?
Cheers,
sudheer
Carmine Daloia wrote:
Jonathan,
Forgot to mention, that the performance aspects of carrying OAM type
signals over an IP based control channel in LMP-WDM would have to be analyzed.
It is possible that the IP Control Channel will not provide fast enough
transfer to actually suppress downstream alarms, however that needs to
be analyzed as part of LMP-WDM.
Thanks
Carmine
Carmine Daloia wrote:
3BFBA9CC.1060609@lucent.com">Jonathan,
The LMP-WDM document specifies the signaling between the Cross-connect
and OLS, assuming they are from different vendors. If they are from different
vendors, then a standard interface is needed to exchange some information.
One type of information that would need to be exchanged is some OAM signals.
Maarten described some of these signals in his VBI document. However, I
don't see why OAM signals would have to be exchanged directly between the
cross-connects themselves via LMP.
Let's look at the following network.
OXC1 --- OLSA --- OXC2 --- OLSB --- OXC3 --- OLSC --- OXC4
Note that the OLS consists of DWDM Mux/Dmux Terminals and Optical Amplifiers.
Let's assume a failure on OLSA. OLSA via overhead within an OSC suppresses
alarms within OLSA. OAM messages (e.g., Optical Channel FDI) could be carried
over the LMP-WDM control channel to OXC2. OXC2 will have to forward the
FDI signals downstream over the LMP-WDM control channel to OLSB. OLSB will
then forward these FDI signals over its OSC and then over the LMP-WDM control
channel to OXC3..... etc...
Note that OXC2 does not need to directly forward these FDI signals to
OXC3. So it is possible, that in LMP-WDM, we may need to define messages
corresponding to FDI signals to suppress downstream alarms, however we
don't need to define such messages in LMP.
Thanks
Carmine
Jonathan Lang wrote:
C12BBE1C7A8F7344808CD8C2A345DFB8455B10@pulsar.chromisys.com">
Carmine,
Please see inline.
Thanks,
Jonathan
-----Original Message-----
From: Carmine Daloia [mailto:daloia@lucent.com]
Sent: Monday, November 19, 2001 6:44 AM
To: ccamp@ops.ietf.org
Cc: tsg15q11@itu.int; t1x15@t1.org
Subject: LMP: Suppression of Downstream Alarms...
Hi all,
As I read through Section 6 "Fault Management", one issue that it seems
to be addressing is "Suppression of Downstream Alarms".
In section 6.2, it states that "If data links fail between two PXCs, the
power monitoring system in all of the downstream nodes may detect LOL
and indicate a failure. To avoid multiple alarms stemming from the same
failure, LMP provides a failure noti
fication through the Cha
nn
elStatus
message...".
I agree that the suppression of downstream alarms is an important issue.
great!
If we look at standard networks (both SONET/SDH and OTN), this
capability is already provided by the overhead in SDH/SONET and G.709
OTN. G.709 OTN handles suppression of alarms in both all-optical
networks as well as opaque networks. I don't think we need to burden the
control plane with such functions when the transport plane handles this
in standard networks. In fact the transport plane handles suppression of
alarms on all equipment in the network (not just cross-connects).
If we look at a pre-OTN ("non-standard") scenario consisting of
Cross-connects, Optical Line Systems, and Optical Amplifiers supporting
a DWDM networked solution, we can analyze two scenarios. One scenario is
an opaque network (e.g., the OLS supports 3R). In this scenario, the
downstream Cross-connects would not detect LOL upon faults occurring
upstream. The 3R points on th
e OLS Line Systems would insert some type
of signal dow
ns
tream. Therefore the mechanism described in Section 6.2
does not apply. Another scenario is an all-optical pre-OTN network. Note
that other equipment besides Cross-connects (e.g., Optical Amplifiers)
in an all-optical network may alarm due to upstream faults. These alarms
also need to be suppressed. LMP seems to only address the suppression of
downstream alarms on cross-connects without taking into consideration
the network that sits between the cross-connects. Is LMP also expected
to have to be processed on Optical Amplifiers? This seems to be
undesirable, especially given all the various applications that seem to
be included into the LMP protocol that would not have anything to do
with Optical Amplifieris.
For interaction between cross-connects and Line Systems, please see OLI
Requirements document
(http://search.ietf.org/internet-drafts/draft-many-oli-reqts-00.txt) and
corresponding LMP-WDM protocol document (new version to be uploaded
tomorrow, but old version can be found at
http://search.ietf.org/internet-drafts/draft-fredette-lmp-wdm-02.txt).
Any other views?
Carmine
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