RE: Optical impairments in draft-ietf-mpls-generalized-signaling- 04

[John Drake <jdrake@calient.net>]

The point is that there is always a race condition wrt to resource
availability.  Routing
can give you an acceptable path but signalling tells you whether the
resources along that
path are available at the time the attempt is made to establish the LSP.
Advertising
resource availability information is usually not a good idea as it causes a
flooding load
and doesn't prevent the race condition.  

Advertising impairments in routing and using them to determine whether a
path is feasible
makes sense but advertising wavelength availability or wavelength conversion
capapbility,
if it is a limited resource, doesn't.   

-----Original Message-----
From: Giovanni Fiaschi [mailto:Giovanni.Fiaschi@marconi.com]
Sent: Wednesday, June 27, 2001 8:53 AM
To: John Drake
Cc: 'Heiles Juergen'; John Drake; 'Yangguang Xu'; Diego Caviglia; Ayan
Banerjee; ccamp@ops.ietf.org
Subject: RE: Optical impairments in
draft-ietf-mpls-generalized-signaling- 04




I don't see the point of some calculations during routing and some other
during
signaling.
Either I find during routing a path that works, that is with both wavelength
continuty (if conversion is not allowed in some network sub areas) and
acceptable signal degradation, or I accept crankback or unavailable resource
answers during signaling (when it is too late to attempt alternate routes)
due
to any of wavelength not found or unacceptable signal.






JD:  I think that we might be agreeing with each other;  i.e., impairments
should be handled in routing and wavelength continuity should be handled in
signalling.