RE: Lambda LSP establishment

[John Drake <jdrake@calient.net>]

-----Original Message-----
From: Heiles Juergen [mailto:Juergen.Heiles@icn.siemens.de]
Sent: Thursday, December 13, 2001 2:16 AM
To: John Drake; Maarten Vissers; manoj juneja
Cc: ccamp@ops.ietf.org
Subject: RE: Lambda LSP establishment


Let me express my understanding of FAs in MPLS/GMPLS, please correct me if I
am wrong. I have also some questions related to the label generation and
interactions between layer networks.

The label in MPLS is local to the link between two adjacent MPLS switches,
it indicates a LSP in this link. This link is therefore the ultimate FA. An
already established LSP between two MPLS switches, which don't have to be
adjacent, can be used to transport/tunnel other LSPs between this two nodes.
This already established LSP generates a virtual adjacency between the two
nodes, the FA. As several LSPs can use this FA it is also a kind of virtual
multiplexing.


JD:  What people don't seem to realize is that LSP hierarchy and FAs were
developed for GMPLS and not for MPLS.  In the case of a non-PSC FA, the
virtual multiplexing that you mention is real.


If you compare it with a circuit switched network the FA is a server layer
trail that provides transport (a link connection) for one or more client
layer signals.
In MPLS the FA establishes "virtual" layer networks. In GMPLS the layer
networks already exist (SDH HO/LO-VCs, RS, MS, G.709 ODUs, OCh, OMS, OTS). A
FA basically corresponds to a real trail in a circuit switched network.


JD:  However, that 'real trail' may be established dynamically as an FA and
its path may include two or more MPLS nodes.  To expand on my example of the
other day, one might establish an FA LSP of type TDM and capacity OC-192
across a lambda core and advertise it as being able to multiplex four
OC-48s.  Up to four OC 48 FA LSPs could then be established using this FA
LSP as a link.  Each of these four OC 48s could then be advertised as FA
LSPs and so on. 

  
In GMPLS the label is also local to the link between the two devices that
perform the switching. For example for SDH the VC-N is identified by the
STM-N link/port and the SUKLM number according to
draft-ietf-ccamp-gmpls-sonet-sdh-02.txt. The STM-N port is identified by the
interface ID (I am not sure on this) and SUKLM is the SDH label that locates
the VC within the STM-N.
From just the SDH viewpoint the STM-N connection is the ultimate server
trail/FA. However the STM-N signal could be transported over a Optical
Channel or G.709 ODU. The OCh or ODU can already start in the equipment that
performs the VC-N switching. So the STM-N signal is not the port, but the
WDM signal is the port and the STM-N signal makes use of a OCh or ODU server
layer trail. This server layer trail can be established via management or
using GMPLS. 
Can someone explain how a label for a VC-4 is generated in this case
(pre-established OCh or ODU trail via management or setup using GMPLS). This
interaction between the different technologies/labels need in my view some
further explanation.


JD:  The details of the SONET/SDH hierarchy are, as I've noted previously,
beyond me.  However, the general model is that the head and tail ends of an
FA LSP communicate directly to allocate a label for a given LSP from the
address space of the FA LSP.  If that FA LSP is of type TDM, then the label
will be a SONET/SDH label.


One special thing about the SDH label is, that it includes a hierarchy as it
identifies the lower order VC in a higher order VC in a STM-N signal. Note
that this is somehow in contradiction with a statement in the GMPLS
signaling document which says 
"A Generalized Label only carries a single level of label, i.e., it is
   non-hierarchical.  When multiple levels of label (LSPs within LSPs)
   are required, each LSP must be established separately, see [MPLS-
   HIERARCHY]."
Following this statement each layer should have its own label independent of
server layers.
The combination of hierarchies in labels is based on technology (e.g. SDH,
Sonet, G.709 ODU) but has in my view no real technical reason. The SDH label
for example fits to standard STM-N signals, but not to sub-STM signals.
For the SDH the full SUKLM number is used if a e.g. VC-12 is located in
relation to a STM-N interface. If it is located in relation to a VC-4 (the
VC-4 is in this case a FA) SUK are set to 0. For me it is not clear in which
case I use the first and in which case I use the second case as a VC-4 trail
is always needed for a VC-12 connection. This VC-4 could be established
using management or GMPLS. However it should have no influence on the label.

Some more information is needed in my view in this area.

JD:  You're probably right.


Juergen
 

> -----Original Message-----
> From: John Drake [mailto:jdrake@calient.net]
> Sent: Wednesday, December 12, 2001 6:54 AM
> To: Maarten Vissers; manoj juneja
> Cc: ccamp@ops.ietf.org
> Subject: RE: Lambda LSP establishment
> 
> 
> fortunately, this is just your opinion
> 
> -----Original Message-----
> From: Maarten Vissers [mailto:mvissers@lucent.com]
> Sent: Tuesday, December 11, 2001 9:31 PM
> To: manoj juneja
> Cc: ccamp@ops.ietf.org
> Subject: Re: Lambda LSP establishment
> 
> 
> Manoj,
> 
> Forget the FA stuff, it is not appropriate in circuit 
> networks. It only
> applies
> to MPLS. We should remove it when it is used in relation with PDH,
> SDH/SONET,
> OTN and pre-OTN. The text in sdh-sonet draft should state 
> that if there is a
> LOVC link (IETF: link bundle/TE link) then the LOVC signals 
> use a label with
> "00KLM".
> 
> Regards,
> 
> Maarten
> 
> manoj juneja wrote:
> > 
> > Hi Marteen,
> >             The concept of FA is mentioned for SDH/SONET in 
> gmpls-sdh
> > -sonet draft. It says that if u have a HOVC trail as a FA 
> (advertized
> > as a link) then u can allocate the lower level signals in 
> it by making
> > the higher bits of label as 0s (i.e. S and U}. This is fine 
> for the same
> > technology. What about the case where the TDM LSP has to be tunneled
> through
> > the Lambda LSP ? What will be the form of label (i.e. 
> {SUKLM} or lambda
> > etc.) ?
> > 
> > Regards,
> > manoj.
> > 
> > >From: Maarten Vissers <mvissers@lucent.com>
> > >To: manoj juneja <manojkumarjuneja@hotmail.com>
> > >CC: ccamp@ops.ietf.org
> > >Subject: Re: Lambda LSP establishment
> > >Date: Tue, 11 Dec 2001 15:56:41 +0100
> > >
> > >Manoj,
> > >
> > >You refer to one wavelength to be available between A-E without
> wavelength
> > >conversion capability. This suggests that you operate at 
> the OCh layer
> > >network.
> > >Then you specify the capacity of the 4 OCh link 
> connections (A-B, B-C,
> C-D,
> > >D-E)
> > >to be "C". Say that C is about 10 Gbit/s. You then assume 
> that there is a
> > >request for an OCh signal with capacity C/4 (e.g. 2.5 
> Gbit/s) between C
> and
> > >E.
> > >The result is that the OCh link connections C-D and D-E 
> are transporting
> > >the OCh
> > >signal (of e.g. 2.5G). These OCh link connections are now 
> in service and
> > >not
> > >longer available to an other OCh connection request. I.e. 
> a request for
> an
> > >OCh
> > >connection between A and E will be rejected.
> > >
> > >FAs are not applicable in the circuit layers. IF there is 
> a trail in
> server
> > >layer X, then there is a link in its client layer Y. X and 
> Y are thus
> > >different
> > >layer networks and signals.
> > >
> > >If C-E is a "FA", then in an OTN the C-E connection would 
> be an OCh trail
> > >supporting an ODUk (k=1 if OCh is 2G5) link with a single link
> connection.
> > >
> > >Note a FA in MPLS creates essentially a MPLS sublayer 
> network. Such is
> not
> > >possible in the SDH/SONET, OTN, PDH or ATM technologies.
> > >
> > >Regards,
> > >
> > >Maarten
> > >
> > >OCh link connections
> > >
> > >manoj juneja wrote:
> > > >
> > > > Hi All,
> > > >         If I have 5 nodes A, B, C, D and E connected as 
> shown. Assume
> > > > that only one wavelength is available on the path A to E (no
> wavelength
> > > > conversion capability is there on the complete path). 
> Let the capacity
> > > > of the wavelength be C. Further assume a request arrives for
> connection
> > > > from node C to E for a line capacity of C/4. This 
> request will be
> > > > successful as we have available wavelength. Now If 
> another request
> > > > comes at node A to establish another connection from 
> node A to node E
> > > > via nodes {A,B,C,D,E} for a line capacity of C/4. 
> Should this request
> > > > be successful as we have already allocated the wavelength ?
> > > >
> > > > If the previous connection from C to E of capacity C/4 had been
> > > > advertised as a FA, in that case will the IInd request succeed ?
> > > >
> > > > If the previous connection from C to E of capacity C/4 
> had not been
> > > > advertised as FA then what will be the fate of IInd connection ?
> > > >
> > > >        A <--> B <---> C <----> D <---> <----> E
> > > >
> > > > Regards,
> > > > manoj.
> > > >
> > > > 
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