The MPLS-OPS Archive

[Spice Sylvia <falsesylvia@yahoo.co.uk>]

Hi Amit,
Please see inline
-->
--- Amit 70405 <AmitG@huawei.com> wrote:
> Hi Sylvia,
>    FA is basically a higher bandwidth LSP.
>    On top of this LSP you can  combine(nesting) one
> or more lesser banwidth LSP's.
>    FA provides a kind of abstraction, that is a link
> between FA ingress and egress.
>    Thus hiding the details of that particular
> portion of the network.
> 
--> and what "details" does one hide?
If it is "link identifier" they are link local, if
they are "site identifiers" they are site local, if
they are end point identifiers, they have to be
unique, if the problem is the "table size" you could
do:
N1---N2---N3--N7--N4--N5--N6
     |                 |
     N8-----N10-------N11

and advertise reachability to N6 via the N8 N10 path
to N2 so that N3-->N5 is not used and hence reduce the
table size. 
So what is the exact details one is "hiding" and why
is one hiding the same?


>    There are many scenarios where we need this kind
> of nesting.
> 
>    One of the scenario is Inter-area or Inter-As LSP
> setup.
>    Here an FA is setup in a single area and is used
> by a LSP from another area that need to traverse
> this FA LSP area.
>    Thus the LSP will be setup without knowing the
> details of the FA LSP area.
> 
---> but that is equally valid for above, and if i do
need to setup a constraint based LSP, each
intermediate node which has reachability to the end
point will have to consider all alternate paths, In
other words, why dont I simply "knock" off those boxes
in the middle and do full mesh :) /directly connect N1
to N5?


>  
>    Secondly in GMPLS.
>    Say the backbone is a TDM or a Optical network.
>    And access network is a PSC network.
>    Bandwidth allocation in TDM or Optical will be in
> higher chunk, than what it is in packet.

as far as my knowledge goes, TDM slots can be
allocated per call, that is the bases of how existing
PSTN/Digital Networks work today.

>    So in this case a FA is setup in the Backbone,
> and multiple LSP's from access will start setting up
> over this FA.
> 

That FA is the "wire capacity" in my case, can you
give me one reason where the "stacking/hierarchy
helps". 

I would prefer practical examples, and would prefer if
it was assumed every device in the middle has a
control plane.

>    I hope it helps.
> Regards,
> Amit.

hope that clarifies my question
-brgds
Sylvia 
> 
>    
>    
> 
> ----- Original Message -----
> From: Spice Sylvia <falsesylvia@yahoo.co.uk>
> Date: Tuesday, April 12, 2005 4:43 pm
> Subject: [MPLS-OPS]: Hierarchical LSPs
> 
> > Hi,
> > 
> > Can someone please help me understand why the
> > "capacity" of the wire itself cannot be treated as
> the
> > outer most constrain, rather than making a
> > hierarchical association.
> > 
> > In other words:
> > 
> > N1---N2----N3---N7--N4---N5--N6
> > 
> > I see that folks define a FA from N3 to N4, inside
> > which another FEC from N2 to N5 is created and
> another
> > N1 to N6 hierarchy is put inside it.
> > 
> > Howevr in all cases the CAC/setup is done from N1
> to
> > N6.
> > 
> > Is there a reason why the FEC hierarchy is built?
> Why
> > does the "capacity of the wire" not act as the FEC
> > itself?
> > 
> > Is "maintaining the state" of each inner LSP on
> > intermediate node a problem?
> > 
> > -brgds
> > Sylvia
> > 
> > 
> > Send instant messages to your online friends 
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> > 
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