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Cell Relay Retreat>MPLS WG Archive>month:2002-Nov> msg00045



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Decreasing TE-LSP bandwidth, "interoperability issue" (fwd)

  • From: David Charlap <David.Charlap@marconi.com>
  • Date: Wed, 06 Nov 2002 16:47:22 -0500
  • User-Agent: Mozilla/5.0 (Windows; U; WinNT4.0; en-US; rv:1.1) Gecko/20020826

Houck, David J (David) wrote:
 >
 > I have a question about the "build the new then tear down the old"
 > approach for decreasing TE-LSP bandwidth.  If a link in the path is
 > at capacity, then wouldn't the "build new" request be denied.  If so,
 > it would be a lot easier just to decrease the bandwidth on the
 > existing TE-LSP.

Not if the LSP is signaled using RSVP SE-style.  With SE style, the 
reservations for all LSPs in a single session share a common reservation 
which is normally the least-upper-bound of all the individual 
reservations.  So if the new LSP has less bandwidth than the existing 
LSPs, it won't cause new resources to be reserved, and shouldn't fail.

This assumes, of course, that the hardware and software on the router in 
question is capable of properly implementing SE style.  But all of 
make-before-break depends on this.

-- David