Hi Igor hi Greg,
I think this is a very interesting discussion.
IMHO the point Igor raised is on the boundary between network planning and
circuit provisioning I mean the decision to have a node with/without conversion
capability is a planning decision, likely dependent by a given traffic forecast
and a physical topology. Moreover the same consideration applies for 3R
capabilities I mean is possible that an LSP needs 3R due to optical impairments.
A possible solution to say that loopback are not allowed and thus if an LSP for
some reason needs a loopback the PCE must return an error. This information
can be used to improve the wavelength conversion/3R capability of the network
e.g. planning the deployment of more wavelength converter. The other solution
is to allow loopback.
Best Regards
Diego
________________________________
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Greg Bernstein
Sent: venerdì 28 settembre 2007 23.44
To: Igor Bryskin
Cc: ccamp; [EMAIL PROTECTED]
Subject: Re: [Pce] Some key issues with Wavelength Switched Optical Networks...
Very good catch Igor. See in line.
Igor Bryskin wrote:
--snip--
2. Considering wavelength conversion inevitably brings to the problem of looped
paths, which is a completely new ball game in path computation, and I am
surprised that the issue was never mentioned in the draft.
--> How is this different from the "looping" that can occur with a TDM
multiplexer in a drop and continue mode? Also in these two circuit cases (TDM,
and optical) do we have the same danger as in the packet case where looping
traffic can greatly degrade other flows. Was there some general looping
concerns already published for GMPLS with respect to circuits?
IB>> There is a profound difference. I am not talking here about accidental
looping, rather about deliberate looping: if some nodes can perform wavelength
conversion while others can not, then you will want to route the connection to
one or several conversion points and after that get it back on the main path.
In other words you will deliberately request, say, a PCE to produce looped
path, and then GMPLS RSVP-TE to signal looped path, which is completely out of
normal paradigm of work for both PCE and RSVP.
--> I thought you were worried about accidental loops. I didn't even consider
what you are talking about "looping", but would RSVP processing get fouled up?
It sure looks like a loop at the "node" level.
In the ERO the "node" subobject (IP4, IP6, AS) could definitely be repeated,
but with a different "Label ERO" subobject appended. This is definitely
something somebody would not to in the MPLS or TDM case. I'll be sure to add
it as an important difference in the next revision. Thanks!
Cheers,
Igor
________________________________
--snip--
--
===================================================
Dr Greg Bernstein, Grotto Networking (510) 573-2237
_______________________________________________
Pce mailing list
[email protected]
https://www1.ietf.org/mailman/listinfo/pce
