Re: Lambda LSP establishment

[Maarten Vissers <mvissers@lucent.com>]

Eric,

In a parallel discussion it was concluded that an IETF FA is equivalent to a
G.805 link. And within ASON, routing adjacencies are over G.805 links... i.e.
over an FA in IETF terms.

I believe that we are hitting here a major difference between GMPLS and ASON
(and between GMPLS and existing management plane based connection management
(eMPbCM)).

ASON (and eMPbCM) establish layer network X routing adjacencies between two
layer network X switches which share (i.e. are at the two ends of) a G.805 layer
network X link.

GMPLS establishes routing adjacencies between two equipment which share a
physical medium (e.g. fiber).

This difference in my current understanding may prevent interworking between an
ASON/eMPbCM network and a GMPLS network.

Looking at the document introducing the FA concept
(draft-ietf-mpls-lsp-hierarchy), I noticed that it is a MPLS document and not a
GMPLS document... the document defines a MPLS FA.
A MPLS FA is equivalent to a MPLS serial compound link (G.805); i.e. a serial
concatenation of MPLS links (G.805 terminology). The optical network FA (e.g. a
VC-4 FA supporting a VC-12 link) is different as it represents a server layer
trail supporting a (single hop) link in the layer network of interest.

The MPLS link (G.805) between two adjacent MPLS LSRs is already a (optical
network) FA (ON-FA). And two MPLS LSRs have no doubt a routing adjacency, but as
indicated this adjacency is via an ON-FA... so my conclusion is that routing
adjacencies are also over FAs.

So if MPLS LSRs have routing adjacencies over ON-FAs, then VC-12 switches should
be able to have routing adjacencies over VC-12 links (G.805) which are VC-4 FAs
(IETF).

Regards,

Maarten

"Mannie, Eric" wrote:
> 
> Hello Juergen,
> 
> We already discussed it so many times....
> 
> FAs and links are two different objects. No routing adjacency over an FA
> LSP. FAs are optional. You can route a VC-12 without having any FA. You can
> have mini dummy VC-4 "circuits" just between two adjacent LSRs (VC-4 POH
> terminated in two adjacent SDH/SONET nodes). These mini dummy VC-4 circuits
> will not be seen as customer circuits. They don't need to be seen as FAs.
> 
> Kind regards,
> 
> Eric
> 
> -----Original Message-----
> From: Heiles Juergen [mailto:Juergen.Heiles@icn.siemens.de]
> Sent: Thursday, December 20, 2001 11:04 AM
> To: Mannie, Eric; Heiles Juergen; ''John Drake' '; 'Maarten Vissers ';
> 'manoj juneja '
> Cc: 'ccamp@ops.ietf.org '
> Subject: RE: Lambda LSP establishment
> 
> Hi Eric,
> 
> thanks for the explanation below. I have some further questions for
> clarification and I also think an informational I-D would be helpful.
> 
> You said that from the routing point of view a link and an FA are two
> different things. There is a routing adjacency "over" a link but not over a
> FA.
> I don't see the difference between a "physical link" and a FA as routing can
> use both to establish a connection.
> Furthermore for the SDH case if a VC-12 connection is setup via an existing
> VC-4 connection the VC-4 connection is an FA according to my understanding.
> However if a VC-4 connection is setup over a STM-16, the STM-16 is not a FA,
> it is a link. Is this correct? From the VC-12 or VC-4 routing view point I
> don't see a difference between the FA or link. Furthermore the STM-16
> connection itself could be transported via an OCh or ODUk in a WDM system.
> So it is not the physical interface of the equipment. Is it still a link and
> no FA as from the physical topology only WDM (OTM-n) interfaces are seen.
> 
> Now concerning the setup of a VC-12 over a STM-16. In this case you use the
> full SUKLM number. owever in order to make this connection a VC-4 or HO VC-3
> connection has to be established prior to the VC-12 connection. Is this
> implicitly assumed? After the setup of the VC-12 this V-4 or HO VC-3 exists.
> Is it now seen as a FA?
> Lets have a look on two examples:
> 
> (1) HO/LO(4/1)-DXC <---STM-16---> HO/LO(4/1)-DXC
> 
> (2) HO/LO(4/1)-DXC <---STM-16---> HO(4/4)-DXC <--- STM-16---> HO/LO(4/1)-DXC
> 
> In example 1 two 4/1 SDH cross-connects that support VC-12 and VC-4
> switching are directly interconnected via a STM-16. In this case the VC-12
> label could be defined in relation to the STM-16 interface with the full
> SUKLM set. In the second example the two 4/1 cross-connects are
> interconnected via a 4/4 cross-connect that supports only VC-4 switching. Do
> we need a VC-4 FA in this case between the two 4/1 cross-connects to setup
> the VC-12 connection?
> 
> Regards
> 
> Juergen
> 
> > -----Original Message-----
> > From: Mannie, Eric [mailto:Eric.Mannie@ebone.com]
> > Sent: Thursday, December 13, 2001 6:57 PM
> > To: 'Heiles Juergen '; ''John Drake' '; 'Maarten Vissers '; 'manoj
> > juneja '
> > Cc: 'ccamp@ops.ietf.org '
> > Subject: RE: Lambda LSP establishment
> >
> >
> > Hi All,
> >
> > A few comments,
> >
> > >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.
> >
> > Eric: ...and this trail is setup dynamically using GMPLS. That's the
> > interest. One can think of SDH/SONET FAs as shortcuts or
> > express-routes.
> >
> > >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]."
> >
> > No, hierarchy of labels is not hierarchy of layers. And even
> > one should have
> > a common definition of what means a "layer". This text says
> > that we cannot
> > have multiple embedded labels, e.g. one label containting a
> > label stack.
> > This is a signaling stuff that doesn't imply anything on the transport
> > plane.
> >
> > Now, a label identifies ONE LSP at an interface. This LSP can
> > be HO or LO in
> > SDH. The label can be fully specified or partially specified,
> > depending on
> > the context where the LSP is established.
> >
> > E.g. when an LSP is established over a FA, the highest part
> > of the LSP label
> > is not relevant. When the FA LSP is established the lowest
> > part of the FA
> > LSP label is not relevant.
> >
> > If a low order LSP is established without any higher order
> > FA, the label is
> > fully specified. As you said the link is indeed the "ultimate
> > FA" in that
> > case. Except that from the routing point of view a link and
> > an FA are two
> > different things. There is a routing adjacency "over" a link
> > but not over a
> > FA.
> >
> > The SDH/SONET label just includes what you need to include in
> > each scenario.
> >
> > Moreover, the label MUST be interpreted according to the type
> > of interface
> > for which it is used. It is possible to code two labels
> > having the same
> > value but a complete different meaning. Labels are context
> > sensitive of
> > course.
> >
> > For instance, an LSP over an STM-0 interface or over a FA
> > will have the
> > highest part set to zero, and could possibly have the same
> > lowest part. You
> > cannot understand what means the label without knowning the
> > detail of the
> > interface. In that case, the interface is either an STM-0
> > interface or a
> > VC-3 FA. And of course that FA and STM-0 interface are two
> > different things,
> > but from the LSP point of view, in both cases what it wants
> > is a VC-3 in
> > which it can be multiplexed.
> >
> > Hope this helps.
> >
> > I start to wonder if we should have an informational draft describing
> > different scenarios of SDH/SONET LSP establishment. That
> > could complement
> > the SDH/SONET signaling drafts and the GMPLS architecture.
> > That could solve
> > many terminology and modeling issues.
> >
> > Kind regards,
> >
> > Eric
> >
> > -----Original Message-----
> > From: Heiles Juergen
> > To: 'John Drake'; Maarten Vissers; manoj juneja
> > Cc: ccamp@ops.ietf.org
> > Sent: 12/13/01 11:15 AM
> > 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.
> > 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.
> > 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.
> >
> > 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.
> >
> >
> > 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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