[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Fwd: LSC Interface Doubt ...
Jonathan,
Jonathan Lang wrote:
>
> Maarten,
> Please see inline.
>
> Thanks,
> Jonathan
>
> > -----Original Message-----
> > From: Maarten Vissers [mailto:mvissers@lucent.com]
> > Sent: Friday, December 07, 2001 1:30 AM
> > To: manoj juneja
> > Cc: ccamp@ops.ietf.org
> > Subject: Re: Fwd: LSC Interface Doubt ...
> >
> >
> > Manoj,
> >
> > Are you aware that a PXC can be operated as an ODUk switch or
> > a STM/OC-N switch in addition to an OCh switch?
> >
> > The PXC is a name for an optical fabric equipment. As fabrics are typical
> more
> > transparent than the connected line/trib ports, those latter determine the
> > switching type. E.g. a PXC connected to optical line systems including
> > transponders will not operate at wavelenght level.
> A clarification here is needed. I agree that a PXC with integrated
> transponders can be TDM capable. However, if the OLS is a separate piece of
> equipment (most likely not speaking GMPLS), then from a GMPLS perspective,
> the PXC is doing wavelength switching. Granted the wavelengths actually
> being switched may all be the same wavelength (e.g., 1310), but they are
> still wavelength switched.
The allocation of functions to boxes isn't determining the functionality itself.
The addition of OLI/VBI to the OLS and PXC boxes makes the combination a true
cross connect. I can replace the set of boxes by a single box with an electrical
fabric, and would get the same functionality from the network perspective. As
such the OLS inlcuding 3R transponders makes that the PXC operates as a
STM-N/OC-N/GE switch/cross connect (case of pre-OTN), or as an ODUk switch/cross
connect (case of OTN).
Take another example of bit interleaving... most people are used to this in the
electrical domain; i.e. a parallel/serial converter circuit takes one bit of N
parallel wires and outputs these N bits on a single wire... after this action
the serial signal is these days typically converted into an optical signal...
The alternative is to use OTDM techniques to perform the bit interleaving... the
signals on the N parallel wires are electrically interleaved into signals onto
e.g. 4 wires... the 4 resulting bit streams are then converted into the optical
signals... then the final bit interleaving uses an OTDM circuit...
As can be seen the functionality hasn't changed despite that a complete
different technology is being deployed.
To me this discussion is very helpful. It shows to me that LSC is an ambiguous
term. As the transport plane doesn't have a "lambda" layer network, I believe
that it is time to convert the current terminology of LSC and also TDM into the
real transport layer terminology like OCh, ODUk (k=1,2,3), HOVC
(VC-3,4,4-4c,...) and LOVC (VC-3,2,12,11). If GMPLS is intended to support
connection management in the SDH and OTN networks, it should use the terminology
applicable in these networks.
>
> > The transponders have
> > terminated the wavelengths. Such combination will switch ODUk and/or
> STM/OC-N
> > signals. For the case the line systems do not have transponders, the PXC
> > operates as true OCh (i.e. wavelength) switch.
> agreed, this is an example of 15xx wavelength switching.
>
> >
> > Most line systems in the core network today deploy 10G wavelengths,
> whereas many
> > service signals are at 2G5 level. Therefore, the transponders in the line
> system
> > may include 4:1 TDM multiplex circuits. With future 40G wavelengths, there
> will
> > be 16:1 TDM mux circuits (case of 2G5 services) and 4:1 TDM mux circuits
> (case
> > of 10G services). Here it is more obvious that the PXC doesn't switch
> "wavelengths".
> I don't see the difference here (except higher rates) from the first
> example. Again,
> if the PXC is speaking GMPLS, the PXC can be considered to be doing
> wavelength switching since it is switching (e.g., 1310) wavelengths
> transparently.
A wavelength is never switched. A wavelenght is the representation of a
tributary slot within a WDM signal. When the WDM signal terminates (i.e. in an
OLS) the tributary slot ceases to exist. The optical signal transported via the
trib slot is extracted and forwarded to the PXC. If there is a 3R transponder,
the optical signal is terminated in the OLS also. If there is no 3R transponder,
the optical signal is forwarded and the full capability of the PXC (i.e. to
switch optical signals) is deployed.
GMPLS or ASON isn't having any impact on the transport plane functionality of
the PXC. The PXC managed by a NMS will provide the same transport plane
functionality.
Regards,
Maarten
>
> >
> > Therefore LSC for me is limited to true G.709 OCh switching; i.e. when no
> > transponders are present around the fabric.
> This is not the definition in GMPLS.
>
> >
> > Regards,
> >
s> > Maarten
> >
> > manoj juneja wrote:
> > >
> > > Hi Marteen,
> > > I refer to LSC interface as defined in GMPLS architecture
> > > document (i.e. interface which switch data based on the wavelength on
> > > which the data is received e.g. PXC or OXC which operate at the level
> > > of individual wavelength). I don't think it has any thing to do with
> > > Och (G.709).
> > >
> > > Regards,
> > > manoj.
> > >
> > > >From: Maarten Vissers <mvissers@lucent.com>
> > > >To: manoj juneja <manojkumarjuneja@hotmail.com>
> > > >CC: ccamp@ops.ietf.org
> > > >Subject: Re: Fwd: LSC Interface Doubt ...
> > > >Date: Thu, 06 Dec 2001 11:42:02 +0100
> > > >
> > > >Manoj,
> > > >
> > > >I assume you refer to G.709 OCh connections when you use the term "LSC
> > > >LSP". If
> > > >so, then a bi-directional OCh link connection will use the same OCh
> > > >tributary
> > > >slot in both directions; i.e. the same wavelenght is used for go and
> return
> > > >direction.
> > > >
> > > >Regards,
> > > >
> > > >Maarten
> > > >
> > > >manoj juneja wrote:
> > > > >
> > > > > Hi All,
> > > > > If I need to establish a bi-directional LSC LSP then do I
> > > > > need to configure the remote end wavelengths on an LSC interface ?
> > > > > Is there any case where both the upstream and downstream labels of
> an
> > > > > bi-directional LSC LSP be same ?
> > > > >
> > > > > Regards,
> > > > > manoj.
> > > > >
> > > > >
> > _________________________________________________________________
> > > > > Get your FREE download of MSN Explorer at
> > > >http://explorer.msn.com/intl.asp
> > > ><< mvissers.vcf >>
> > >
> > > _________________________________________________________________
> > > Get your FREE download of MSN Explorer at
> > http://explorer.msn.com/intl.asp
> >
begin:vcard
n:Vissers;Maarten
tel;cell:+31 62 061 3945
tel;fax:+31 35 687 5976
tel;home:+31 35 526 5463
tel;work:+31 35 687 4270
x-mozilla-html:FALSE
org:Optical Network Group;Lucent Technologies Nederland
version:2.1
email;internet:mvissers@lucent.com
title:Consulting Member of Technical Staff
adr;quoted-printable:;;Botterstraat 45=0D=0A=0D=0A;1271 XL Huizen;;;The Netherlands
fn:Maarten Vissers
end:vcard