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Re: New draft on Extra class LSP
vishal,
i concur with the idea expressed here saying "this is
a network operator's choice (or the subject of a BCP)."
from the early beginning we have asked to the community
(ie the user community) if they would like to be guided
in such "policy decisions" and their response was "this
is our business" as such it means that two things either
you list *all the policies* or none of them, since it
is practically impossible to achieve the first one, we
opted(*) for the secund, therefore, here the only remaining
possibility is "guidelines through a bcp, using here the
initial user community input" (**) but before this happens
it would have been of great interest to have first this
input - any other views (also from the user community) ?
(*) the tewg bw discussions gives you a sample of what
such policy definition might generate
(**) i think that the analysis i-d gives a fair overview
of the complexity such policy would imply
thanks,
- dimitri.
Vishal Sharma wrote:
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 -
--
Papadimitriou Dimitri
E-mail : dimitri.papadimitriou@alcatel.be
Private: http://www.rc.bel.alcatel.be/~papadimd/index.html
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