The MPLS-OPS Archive

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

Hello Aamer,
 
> On Oct 25, 2004, at 1:06 AM, Spice Sylvia wrote:
> 
> > Hi Aamer,
> >
> >
> >  --- Aamer Akhter <aakhter@cisco.com> wrote:
> >>
> >> On Oct 21, 2004, at 4:29 AM, Spice Sylvia wrote:
> >>
> >>> Hello,
> >>>
> >>> Is there a reason why the LSP setup computation
> >> using
> >>> RSVP-TE is done on the head end and not node by
> >> node?
> >>
> >> As RSVP-TE uses (the information) from the IGP
> >> topology it has the
> >> information it needs to compute the path (and
> match
> >> it with the best
> >> path request). Regardless, the path still has to
> be
> >> verified node by
> >> node, and the nodes still have an opportunity to
> >> decline the
> >> reservation (which triggers an igp update). It
> >> should be noted that
> >> there are way to ways (loose ero) to distribute
> the
> >> path decision at
> >> explicit places in the path.
> >
> >
> >
> > Say I wish to set up an LSP from A to B with the
> > constraint that the number of hops should be x.
> > Why is node by node computation not feasable in
> this
> > case?
> 
> i'm not sure if the question is a theoretical one or
> a practical one. 
> i'm guessing theoretical, afaik because a constraint
> of 'number of 
> hops' isn't carried in the reservation
> 
> unless you have something like ant routing, i don't
> see how you can 
> define a constraint of hop-count and let the
> decision be distributed 
> hop by hop. now if each node had a topology
> database, it could make 
> that kind of decision hop-by-hop as long as the
> constraint was carried 
> hop by hop as well. but if you already have a
> topology database, why 
> try to do this computation hop-by-hop in the first
> place? the 
> initiating node has all the information via it's
> instance of the 
> topology database.

Consider the case of an interarea or interas LSP
setup,
How exactly do people address this problem? 

I do not like to sit and write EROs for customer LSPs
:(( 
Is there a better method you can recommend?

-Sylvia


	
	
		
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