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Re: Suppression of Downstream Alarms...

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 notification through the Chann
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 the OLS Line Systems would insert some type 
of signal downs
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