Re: I-D ACTION:draft-takacs-asym-bw-lsp-00.txt

[Igor Bryskin <i_bryskin@yahoo.com>]

Adrian and Dimitri,

When a GMPLS tunnel is setup, it is setup for a reason.  Let's say, management plane requests a tunnel ingress node to setup a tunnel. The request may not (and normally does not) contain an explicit path, but it definitely contains all bandwidth parameters, because the tunnel was requested, as I siad,  for a particular reason  (application, SLA, etc.). Also, how else you can ensure the fate sharing other than computing a path on the ingress node taking in consideration the bandwidth requirements for both directions?
So, yes, I'd say that it is safe to assume that ingress node always knows about bandiwidth in both directions.

I'd say even more. We have a strict requirement from our customers that actively deploy our GMPLS CP, that a communication between management and control plane should always hapen at one (ingress) node.

Igor

PS It would be interesting to hear from providers on this
 topic.

Dimitri.Papadimitriou@alcatel-lucent.be wrote:

"Adrian Farrel"
04/03/2007 00:35
Please respond to "Adrian Farrel"

To: "Igor Bryskin" , Dimitri
PAPADIMITRIOU/BE/ALCATEL@ALCATEL
cc: , "Don Fedyk"
Subject: Re: I-D ACTION:draft-takacs-asym-bw-lsp-00.txt


> 3. if a) is selected there is no other choice than an upstream flowspec
in
> the Path msg and a upstream tspec in the Resv message

That *does* raise an interesting question. Namely, does the ingress know
the
bandwidth to request? If it does then there is no need for a TSpec on the
Resv as the reservation has already been made commensurate with the
FlowSpec
on the Path.

-> if you do that you prevent the ingress-side to never adapt resource
reservation to the traffic parameters of the egress (in fact, it would
boil down to "single-sided" asymmetry forever)

-> hence, initially you must satisfy at least condition where flowspec
=< tspec, nevertheless, after the tspec may "increase" and therefore
the flowspec may be adapted

If the ingress does *not* know and needs to see a TSpec from the egress,
then we need another Path exchange after the Resv in order to make the
actual reservations. In that case it really would be a mess and not worth
trying to shoe-horn into a bidirectional LSP format.

-> this is what i said also to don, the case where initially the ingress
is completely unaware of what it can reserve is impossible without major
protocol modifications

-> my partial conclusion, is that a workable asym bw lsp doesn't elevate
the need for the general case, and only provides apparent facilitation in
a corner case, whereas a technique making use of association object would
prevent all this protocol massaging, keep full backward compatibility, and
provide full flexibility


A

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