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

From: "MEURIC Julien RD-CORE-LAN" <[email-masked]>
Date: Mon, 5 Mar 2007 15:03:47 +0100

Hi all.

To answer the 1st question, I would say that there is a requirement for
asymmetrical bidirectional *service* (think about IP TV transport for
instance). What is more, as Igor said, being able to handle both
directions as a single service brings advantages (such as fate sharing),
especially in terms of operating a network. Question is: does this
necessarily map to "single LSP"? Not so sure...

Then, I do not see any strong requirement for having a single signalling
exchange. Besides, I do not think a scenario with a management system
communicating with both end-nodes should be excluded neither. However,
in this case, it may be detrimental for the control plane to rely on an
external party to correlate both directions.

Diego, to answer you, I think you are correct: re-using the RRO of the
1st one is an option to consider when routing by the controling plane,
and using management-built ERO for both directions is valid in case of
manual routing. As a result, it looks like tools are there to for
provisioning, nevertheless it may bring an issue to guarantee fate
sharing in case of recovery.

Regards,

Julien

________________________________

From: [email-masked] [mailto:[email-masked]] On
Behalf Of Diego Caviglia (GA/ERI)

From my experience I can quote everything Igor said.  GMPLS tunnel
establishment is, AFAIK, always driven by the NMS/OSS that (quoting Neil
Harrison here) is the King.

So I think that in the real world the Ingress node knows the upstream
and downstream bandwidth of the GMPLS Tunnel is going to set-up.

Moreover if I'll use two uni-directional LSPs in order to set-up an LSP
with asymmetrical bandwidth requirement I can force the path of the two
LSPs to be the same?  Do I have to use the RRO of the first one as ERO
for the second one?  Or I suppose to use a fully defined ERO for both
the two LSP?  In this case I do suppose that the ERO has been calculated
by the NMS?

Regards

Diego

________________________________

From: [email-masked] [mailto:[email-masked]] On
Behalf Of Igor Bryskin

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.

[email-masked] 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