Re: Suppression of Downstream Alarms...

[Carmine Daloia <[e-mail]>]

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:

>Carmine,
>  Please see inline.
>
>Thanks,
>Jonathan
>
>>-----Original Message-----
>>From: Carmine Daloia [mailto:[e-mail]]
>>Sent: Monday, November 19, 2001 6:44 AM
>>To: [e-mail]
>>Cc: [e-mail]; [e-mail]
>>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 ChannelStatus 
>>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 downstream. 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
>>