RE: New draft on Extra class LSP

["Vishal Sharma" <v.sharma@ieee.org>]

Adrian,

Please see my reply to Dimitri.

I agree that priority could be used to setup LSPs that use the
resources reserved (but not cross-connected) for recovery.

However, the end-effect one wants to achieve is to have these
LSPs be pre-empted by no other than working LSPs that legitimately
need to use those resources when a fault affecting those working
LSPs occurs.

As I said in that note, perhaps it is indeed possible, by
an appropriate choice of priority allocations and rules, to achieve
this effect, but it appears to me that this is an area worth some
thought, which the extra-class LSP draft seems to have initiated.

-Vishal


> -----Original Message-----
> From: owner-ccamp@ops.ietf.org [mailto:owner-ccamp@ops.ietf.org]On
> Behalf Of Adrian Farrel
> Sent: Saturday, July 05, 2003 10:46 AM
> To: Dimitri.Papadimitriou@alcatel.be; v.sharma@ieee.org
> Cc: Kohei Shiomoto; ccamp@ops.ietf.org
> Subject: Re: New draft on Extra class LSP
>
>
> I agree with Dimitri here.
>
> There is no reason to assume that (the resources for) a protection LSP
> should not pre-empted by some other LSP. That is the nature of pre-emption
> and it is a Good Thing (TM).
>
> Just as the working LSP might itself be pre-empted, so might the
> protection
> LSP.
>
> One might invent all sorts of schemes to help manage this (such as making
> protection LSPs operate at a higher priority than working LSPs),
> but this is
> a network operator's choice (or the subject of a BCP). No new
> protocol would
> appear to be necessary to manage this.
>
> Adrian
>
> ----- Original Message -----
> From: <Dimitri.Papadimitriou@alcatel.be>
>
> > > In the latter case, however, the only way any traffic could use the
> > > reserved resources would be for one to setup a low-priority,
> pre-emptible
> > > LSP using those resources, with the distinction that these particular
> > > low-priority LSPs are not subject to pre-emption unless a working
> > > LSP that needs to use those reserved resources fails (This what
> > > Shiomoto-san more accurately calls "extra-LSP".)
> >
> > the point is to have a network wide homogeneous allocation
> > of resources, starting to have allocation based on the
> > reason why the lower priority lsp can be preempted leads you
> > to the issue of how many of such conditions can we have
> > in a network ? or do you plan to start defining one class
> > of lsp and priority per such event ? the idea behind the
> > "re-use" of these preemptible resources is to abstract its
> > complexity not to spread it network wide - this while what
> > we have today works perfectly -
>
>