Thanks,
John
-----Original Message-----
From: Shiba, Sidney [mailto:sidney.shiba@us.fujitsu.com]
Sent: Monday, October 31, 2005 7:25 AM
To: Drake, John E; dpapadimitriou@psg.com
Cc: Adrian Farrel; richard.rabbat@us.fujitsu.com; ccamp@ops.ietf.org
Subject: RE: comments on
draft-shiba-ccamp-gmpls-lambda-labels-00.txt
Hi John,
Optical switches based on Wavelength Selective Switch (WSS)
technology
requires the wavelength information for switching. This
technology is
NOT
wavelength agnostic.
| |
| wdm | wdm
|2 |2
--------- ---------
wdm 1| optical |3 wdm 1| optical |3 wdm
--------| switch |------------| switch |---------
| (WSS) | | (WSS) |
--------- ---------
|4 |4
| wdm | wdm
| |
Note that the figure above shows an example of two optical switches
interconnect
by a single WDM fiber. In this example, each optical switch can be
connect
to 4
other optical switches.
As you can see, the optical ports information do not provide enough
information
for wavelength switching.
Hope that clarifies the application requirement.
Thanks,
Sidney
-----Original Message-----
From: Drake, John E [mailto:John.E.Drake2@boeing.com]
Sent: Friday, October 28, 2005 5:33 PM
To: dpapadimitriou@psg.com; Shiba, Sidney
Cc: Adrian Farrel; richard.rabbat@us.fujitsu.com;
ccamp@ops.ietf.org
Subject: RE: comments on
draft-shiba-ccamp-gmpls-lambda-labels-00.txt
Hi,
Below is the text of an e-mail is sent to the
Ethernet/GMPLS mailing
list.
Upon reflection I am not sure using a real wavelength value makes
much
sense. Between a pair of adjacent nodes, there may be
multiple pairs of
switch ports in the same TE link that support a given
frequency. If
a
real wavelength value is used, how do the two nodes agree on
which pair
of switch ports to use?
Furthermore, the amount of configuration is the same - you
still need to
configure the wavelength of each switch port.
Thanks,
John
==============================================================
==========
====
Adrian,
In the transparent photonic lambda switch case, the
labels also have
only local significance. When an LSP is established, the input
ports,
as identified with local labels, are cross-connected to the output
ports, as identified with local labels.
There is just extra configuration to identify, using
strictly local
identifiers, the wavelength associated with the all of
the switch's
ports, and an additional CAC requirement that the
wavelengths of the
input and output ports are the same.
Thanks,
John
-----Original Message-----
From: dimitri papadimitriou [mailto:dpapadimitriou@psg.com]
Sent: Thursday, October 27, 2005 10:03 AM
To: Shiba, Sidney
Cc: dimitri.papadimitriou@alcatel.be; Adrian Farrel;
richard.rabbat@us.fujitsu.com; ccamp@ops.ietf.org
Subject: Re: comments on
draft-shiba-ccamp-gmpls-lambda-labels-00.txt
shiba - see inline for some additional hints:
Shiba, Sidney wrote:
Adrian, Dimitri,
Thanks for reviewing these I-D.
Wavelength continuity constraint does require the use of
semanticful
label whether it is spectral or index.
=> see my reply to adrian on this specific point
I agree with Dimitri that the
wavelength indexing requires document updating each
time a new
spectrum is introduced.
=> indeed and in addition it requires updating the already
signaled path
The use of spectral label provides self maintainance, i.e.,
no need to update any document and the use of the
nominal value
provides a common semantic ground.
=> what do you mean by self-maintenance - would you provide a
bit more detail
[Sidney]What I've meant here was that it was not necessary to
update any document when new wavelengths are
inventoried. In the
case of indexing approach, it would require the
wavelength indexing
document to be updated with implementation impacts.
In the case, the nominal value is used, there is no need for
documentation update.
ok - what you mean here is that you are going to make use of the
already
defined C-Type 2 - what about the specific encoding of the
value space
?
=> now i have a more specific question before being light-up
how do you know the frequency that you can support ?
[Sidney] Some new technologies integrate optical switch and
mux/demux
capabilities, which allows the equipment to know the
spectrum it
supports.
indeed - but the question is what does happen if the
"detected" values
(during initialization) do not match the nominal values ? you
don't
initialize then ?
if these differ from the nominal values how are you going to
deal
with
these
discrepancies ?
[Sidney] These new technologies uses the nominal value as
reference.
We
can say
that a lightpath wavelength is identified by its
nominal value.
If
the
equipment
is drifting from this nominal value, it is considered as
a failure.
ok - but if the deviation is such you have overlap - how the
control
plane is going to be able to detect such failure ?
this said i am not necessarily sure that having to
maintain the data
plane
specifics as part of the control plane is really helping
operations (is this method not just duplicating complexity ?)
[Sidney] The wavelength is WDM specific as much as the SUKLM
label
encoding
is for SONET. The wavelegth/frequency nominal value is used to
identify
the
facilities to cross-connect.
there is an equivalence but there is also a major
difference, the
structure is invariant independently of the state of the
network, with
spectral value space you may have labels that become unavailable
due
to
non-local usage of wavelength in the network
hence, there is also no real coupling to the data plane
more than
knowing the type of interface and some generic capabilities
I'm not sure if the draft needs to be updated before the
face-to-face meeting or after all comments are collected.
Please
advise.
=> suggest to keep discussion on - document update can be
performed at a later stage
thanks,
- dimitri.
-----Original Message-----
From: owner-ccamp@ops.ietf.org
[mailto:owner-ccamp@ops.ietf.org]On
Behalf Of Adrian Farrel
Sent: Thursday, October 27, 2005 4:45 AM
To: dpapadimitriou@psg.com;
dimitri.papadimitriou@alcatel.be;
ccamp@ops.ietf.org
Subject: Re: comments on
draft-shiba-ccamp-gmpls-lambda-labels-00.txt
Dimitri,
Thanks for your work reviewing these recent I-Ds. It is
really valuable
and I'd welcome other people doing similar reviews.
there is a specific point to be clarified in this document:
semanticless vs semanticful label (even here there is a
distinction
between spectral vs indexes i.e. using the
wavelength index)
domain-wide vs link local significant label
Without being too picky, I think all labels are semanticful
otherwise, we
would not know what resource they refered to.
So the point reduces to whether the scope of the semantics
are link-local
or wider.
so, the comparison from this perspective with TDM labels is
difficult to
parse, the latter is semanticful but link local
now, i don't specifically see what has changed the
late 90's,
early
y2k's, to have a change in the wavelength label definition;
This is the question I would like to get to the
bottom of. In
other words:
do we need this function?
It seems to me that the question being asked is this:
If I want to compute a path that has some form of
wavelength
constraints, what information do I need access to?
Another question might be:
If I want to signal a path with wavelength
constraints what
information do I need to include in the signaling message?
I'd suggest that when we started on GMPLS, we were
enthusiastic about
transparent optical networks, but we were not properly
focusing wavelength
constraints because lambda-switching PXCs didn't take off.
Therefore we
didn't examine the requirements for wavelength
constraints in
routing and
signaling. The authors of this I-D are claiming new hardware
requirements
for the same function.
there are
several solution possible
- absolute values: the freq. of the wavelength:
difficult to
adopt
because referenced values are nominal and knowing all
interactions
between wavelengths this knowledge is at the end of little
practical
usage; (introduces implicit ordering)
- indexed values: the # of the wavelength: it does not
provide for a
future proof label space for inst. in case new frequencies
are inserted
in the grid (introduces explicit ordering)
- diff. values e.g. freq spacing starting from a reference
value: pauses
the question of the reference value and does
suffer from the
former
issue (introduces implicit ordering)
- the solution available today - cumbersome in some
control plane
operations (e.g. label set translation) and not easy to
troubleshoot but
independent of any physical consideration (spectral), scale
to
any
number of wavelength per fiber, does not introduce any
ordering, the
most flexible (since allowing each system to maintain its
specific
control operations) and the less constraining since
maintaining
the
control plane operations independent of any data plane
specifics
<http://www.ietf.org/internet-drafts/draft-shiba-ccamp-gmpls-l
ambda-labels
-00.txt>
.
.