Re: LMP vs. NTIP vs. "funiculus"

[Maarten Vissers <mvissers@lucent.com>]

When looking at the LMP work I am have the impression at the moment that
it is partly duplicating capabilities already present in the transport
plane.

The transport plane supports a "single fault, single alarm" capability
via its alarm suppression mechanism (AIS, FDI), as well as a "single
ended maintenance" capability via its remote signals mechanism (RDI/REI,
BDI/BEI).

With the introduction of optical fabric equipment (referred to as PXC or
OXC) an extension of the transport plane's operation is required. In the
past a "fabric" itself was never a stand-alone piece of equipment; it
was always surrounded by interface port units. The interconnect between
interface port unit and fabric unit was implemented as the backplane
within equipment.

With the separation of the interface port units from the fabric unit(s),
the backplane interface is becoming an external interface and needs to
be addressed in standards to guarantee interworking over this interface.

Within ITU-T SG15, this interface has been introduced by me some time
ago as the "funiculus" (umbilical cord) between the optical line system
(OLS, DWDM) and the optical fabric (OXC). It is envisaged to be part of
a new "Line-Fabric (LF)" interface OTM-LF, which is to be developed in
Q.11/15. 

Signals envisaged to go over it are:

- Forward Defect Indication (FDI) signal: 
	On detection of a transmission fault in the incoming
	(aggregate and/or tributary) signal(s), AIS is inserted
	in the downstream direction (towards the fabric card) in
	all tributary signals impacted by the fault - i.e. the
	FDI maintenance signal is transmitted in an in-band manner.
	If an interface port doesn't support this AIS insertion, an
	external FDI message is to be forwarded along the connection
	of the original signal.
	Also, if a signal fail condition is detected in the fabric, 
	FDI should be send downstream.
- Signal Fail, Signal Degrade status signal:
	On detection of a signal fail (SF) or signal degrade (SD)
	defect condition in the aggregate signal or in one or more
	of the tributary signals, a SF/SD indication signal (one per
	failed/degraded tributary signal) is send to the Fabric card
	via the backplane maintenance signal interface to initiate
	e.g. protection switching (transport plane) or restoration
	(control plane), and to provide status information on the 
	link connections (OK, FAIL and perhaps DEGRADE).
- Automatic Protection Switch (APS) signal:
	For the case of bi-directional protection switching, 
	the APS signal (of the aggregate) or APS signals of the 
	tributary signals are extracted in the port unit and send
	to the Fabric unit to coordinate bridge/selector operation
	at head end and tail end of the protected domain.
- Open Connection Indication signal:
	For the case an output port of the Fabric is not connected
	to an input port of the fabric, the Fabric will output an
	"Open Connection Indication (OCI)" maintenance signal to the
	interface port card suppressing the LOS alarm and to forward
	this information to downstream equipment.
- RDI/REI, BDI/DEI remote maintenance signals:
	For the case the protection implementation does not comply
	with its protection switch functional model (see for models
	T1X1.5/2000-079), RDI and REI information should be
	communicated to the Fabric, which will select the RDI/REI
	information from the "active" interface port card and forward
	this to both upstream "working" and "protection" interface
	port cards. 

In addition, this funiculus may have to include one or more management
comms channels (e.g. data communication channel, signalling
communication channel). If the network is a switched network, the
control plane will have to control a subset of the termination point
parameters (e.g. Expected Trace Identifier, error rate threshold,
TP-mode or ARC-mode, protection monitoring option (non-intrusive, tandem
connection), tandem connection monitoring, etc). If the control plane
process resides on the Fabric equipment, then this termination point
provisioning information has to be forwarded to the interface port cards
in the OLS.

Regards,

Maarten
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