RE: Additional Error Handling scenario for draft-ietf-tewg-diff-t e-proto-

[Francois Le Faucheur <flefauch@cisco.com>]

Dimitry,

At 11:22 29/03/2002 -0500, Dimitry Haskin wrote:
>As a side note, I don't believe that meaningful use of CTs in the DiffServ
>context is possible without LSR knowledge of relationship between PSCs and
>CTs (nothing fancy about this). After all, advertising available bandwidth
>in a particular TE class, is the way for an LSR to indicate what is
>available at this LSR for a particular class of service.
>
>In addition to adding text to deal with CT-PSC discrepancies, I'd also
>suggest that the text specifying what CT is to be assumed if the CT object
>is not present in the Path message is modify with something in line with
>below:
>
>"If the CLASSTYPE object is not present in the Path message and relationship
>between PSCs and CTs is known, the LSR should assume CT that corresponds to
>PSC of the LSP tunnel. If the CLASSTYPE object is not present in the Path
>message and relationship between PSCs and CTs is not known, the CT 0 must be
>assumed."

This does not work for E-LSPs (with preconfigured EXP<-->PHB Mapping) since 
there is no signaled PSC.
Current solution works for both L-LSPs and E-LSPs as well as mix of those.
We thought that would "simplify some deployments" 8^). No?

Francois


>Hopefully it may simplify some deployments.
>
>Dimitry
>
> > -----Original Message-----
> > From: Francois Le Faucheur [mailto:flefauch@cisco.com]
> > Sent: Tuesday, March 19, 2002 11:30 AM
> > To: te-wg@ops.ietf.org
> > Cc: flefauch@europe.cisco.com
> > Subject: Additional Error Handling scenario for
> > draft-ietf-tewg-diff-te-proto-
> >
> >
> > Hi,
> >
> > I got a similar comment from two people about a potential
> > inconsistency
> > between CT and PSC which could arise in some cases.
> >
> > To address that, we could add some text explaining that in
> > the case where:
> >       - L-LSPs are used
> >       - an intermediate LSR happens to have some local
> > knowledge of relationship
> > between PSCs and CTs (e.g. because the LSR implements some
> > fancy scheduler
> > weights adjustments)
> >       - the PSC and CT signaled are inconsitent with the
> > local knowledge of
> > PSC/CT relationbship,
> > then the LSR must reject the setup and send Error Message "xyz".
> >
> > Thoughts/comments/concerns about that?
> >
> > Cheers
> >
> > Francois
> >
> >