RE: GMPLS issues (was - GMPLS Last Calls)

[neil.2.harrison@bt.com]

Hi John,

You observed 13 June 2001 16:20
> 
> Niel,
> 
> I think that the point that Eric was trying to make is that 
> the IETF isn't
> the correct venue
> for a PNNI based solution, although a PNNI based solution might be a
> perfectly fine thing.
NH=> Many thanks for acknowledging this.......and as both a signalling
expert and co-author of the PNNI specification your view should carry some
weight.
> 
> From a technical perspective, unless things have changed in 
> the past several
> years, the issues
> with using PNNI are its lack of support for 
> pre-emption/priority and make
> before break, and that
> its bandwidth advertisements are tightly coupled to ATM 
> service categories.
NH=> But PNNI seems as though it can more easily adapted to the required
job.  It has certain features that make it quite attractive like:
-	mature/tested, already deployed and understood
-	proven carrier-strength
-	multiple interfaces already specified, ie UNI, E-NNI, I-NNI, AINI
-	separate link and signalling protocols, eg SSCOP keepalives separate
from signalling, allows more physical interfaces not just connections per
interface
-	supports crankback.....something now slated to be addded to
RSVP/CR-LDP I assume?
-	supports static routed interfaces (AINI)....seems essential for
inter-operator case;
-	support for address translation
-	supports S-PVC-type service
-	Logical Group Node concept provides powerful features, eg hides
interior behaviour, allows centralised signalling and/or path computation,
border nodes not burdened with higher layers, supports any topology, each
peer group can have a different internal behaviour, etc;
-	good for phased migration (this is an importnat issue for
operators);
-	centralised route computation may be better for OTNs.....this would
be allowed;
-	separate signalling and routing means just signalling part can be
used
-	etc

It would, however, need some minor additional work to adapt it for SDH/OTN
as you note......like BW advertisements.
BTW- we have significant experience of trying to run multiple pre-emption
schemes and found it not so useful.  So this is one aspect we would want,
and if it was present we would want to be able to turn it off.

Regards, Neil