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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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