Subject: RE: draft-meyer-mpls-soft-preemption-00.txt

From: "Nguyen, An" <[email-masked]>
Date: Wed, 19 Feb 2003 20:00:10 -0500

Hi all,

The draft is interesting. I wonder if this concept can be implemented to
transport critial traffic for customers in the MPLS network.

Thanks,

An Nguyen

-----Original Message-----
From: Curtis Villamizar
To: Jim Boyle
Cc: Matthew Meyer; [email-masked]
Sent: 2/19/03 4:39 PM
Subject: Re: draft-meyer-mpls-soft-preemption-00.txt 

In message <[email-masked]>, Jim
Boyle 
writes:
> 
> First, great draft - I like this concept.
> 
> While a flag might be just the right thing for this particular
> application, I wonder if it might be good to try to broaden 
> soft preemption technique to include other polite preemptions.
> 
> These might include the following indicators
> 
> o) your LSP is being prempted on the indicated link (draft covers)
> o) your LSP should be rerouted, this node is shutting down
> o) your LSP should be rerouted, this link is being taken out of
>    service
> o) your LSP should be rerouted away from this node
(administrative/CLI)
> o) your LSP should be rerouted away from this link
(administrative/CLI)
> 
> You can somewhat do some of these by changing metrics and waiting, but
> just was wondering if something more general might be useful.

Why couldn't you just use the same bit and allow soft preemption on
link shut, reload, CLI adminstrative without encoding the reason?
Since these are all CLI initiated, it wouldn't hurt to delay.
Alternately, the soft preempt on anything using a specific resource
could be done.

Link bundle lost a member might also qualify as a reason for soft
preemption for implementations of link bundling that can trasnparently
more flows to other members of the bundle.

> Also, with Diffserv TE, not sure that one can assume that a preemption
> necessarily "implies exhausted bandwidth at the affected priority
> level *and greater*" (section 5), but local implementations can do
> as they please I suppose.

Agreed.  The "and greater" should be dropped.

> regards,
> Jim

Thanks,

Curtis

---

From: Ina Minei <[email-masked]>
Date: Wed, 19 Feb 2003 18:19:46 -0800 (PST)

I am not sure what you mean by critical.
	If "critical" implies zero loss always, then the answer is no.
Please note  that this scheme relies on a timer to do hard preemption
regardless of  whether the head end managed to resignal the LSP or not.It
is true that  this timer can be user configurable, but note that in the
scheme presented  this can be done in a scalable fashion only at node
level and not at LSP level (since the head end does not signal the amount
of time at LSP setup time).

	The proposed scheme will be beneficial, but cannot offer any hard
guarantees.

		Thanks,

			Ina