Cell Relay Archive

["Jon L. Gauthier" <jon.gauthier@home.com>]

Soft PVCs are not proprietary anymore - the ITU and the ATMF adopted a
standard/recommendation, and virtually all vendors have implemented it
(and interoperability testing has already been done).

gsundar@home.com wrote:
> 
> > > The other reason for SPVCs over PVCs is in link failure situations.
> > > PVCs by definition do not reroute.  If the failed portion of the circuit
> > > is over non self-healing facilities (not SONET or SDH), you're SOL. PVCs
> > > have no re-routing mechanism - they depend totally on the underlying
> > > SONET layer to provide fault tolerance.  Various manufacturers overcame
> > > that "flaw" with proprietary means, and the ITU and ATM Forum
> > > consolidated them into a standard (or recommendation, in ATMF-speak).
> > > SPVCs, since they are SVCs, will attempt to re-setup the connection
> > > first over the failed link, and then via alternate routes.
> > >
> >
> > soft pvc recovery from failure is the responsibility of the "owner" of
> > the soft pvc and is optional and requires that the owner attempt to
> > reinitiate setup of the connection.  the recovery scheme for soft pvc's
> > has whatever means are made available in pnni (which means crankback
> > procedures, to my knowledge).
> 
> Again : this recovery is a connection setup time recovery, whereas
> the self-healing SONET/SDH is not confined to just connection setup
> time. As someone pointed out, we need proprietary methods to simulate
> SONET kinda recovery on Soft Pvcs (by having a proxy user who will
> check the sanity of the link even after it's setup - as per a previous
> posting about one such mechanism on GDC switches ?).
> So aren't we talking about different things : SONET self-healing is
> a 'real time' (in the sense of being monitored continuously *after*
> the Setup) whereas in the case of Spvc or Svc's it's only during
> Setup time ?
> 
> - Sundar
> 
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-- 
===========================================================
Jon Gauthier
Principal Network Engineer
(for some un-named ATM switch vendor)
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