Re: Draft on constraint-based routing
Bala Rajagopalan <braja@ccrl.nj.nec.com> Fri, 05 February 1999 16:03 UTC
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Date: Fri, 05 Feb 1999 10:53:17 -0500
From: Bala Rajagopalan <braja@ccrl.nj.nec.com>
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To: "Guo, Liang" <guol@ccs.neu.edu>
CC: Yao-Min Chen <ychen@fla.fujitsu.com>, qosr@newbridge.com
Subject: Re: Draft on constraint-based routing
References: <Pine.GSU.4.05.9902042033490.13428-100000@taboor.ccs.neu.edu>
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"Guo, Liang" wrote: > On Thu, 4 Feb 1999, Yao-Min Chen wrote: > > > It seems reasonable to run in parallel best-effot and > > QoS routing protocols. The mechanism described > > in the proposal is described as "overlay" because > > QoS routing relies on link state info collected by the > > best effort routing protocol. The info is used to > > compute the MST. It seems that the proposal chose > > MST instead of other types of spanning trees because > > nodes can individually compute but the computations > > will lead to exactly the same tree, which is important > > to the correct operation of the proposal. Other than this, > > is there any strong empirical or analytical reason > > why MST should be used? Another type of spanning tree > > may be a min-hop one where the max number > > of hops between any pair of nodes along the tree is > > minimized. Since the draft requires reliable > > transmission between neighboring nodes at the QoS > > routing layer, per-hop delay may be significant. > > By reducing number of hops one can > > reduce the latency when some routing update > > needs to be propagated along the tree to all nodes. > > > > Rgds, > > Yao-Min > > > > A good reason could be the simplicity of the MST algorithm, > it's impractical to use a steiner tree or "min-diameter" tree > to transmit control messages since both these trees are hard > to compute, heuristics to these trees are usually time-consuming. > > Guo, Liang > > This is exactly the case. You could compute per-source trees, but this requires larger forwarding tables. Please see the reference on efficient link state QoS-based routing, http://homepages.infoseek.com/~balarajagopalan/qoslinkstate.ps Regards, Bala -- Bala Rajagopalan NEC C&C Research Labs 4 Independence Way Princeton, NJ 08540, USA Ph: +1-609-951-2969 Email: braja@ccrl.nj.nec.com
- Draft on constraint-based routing Bala Rajagopalan
- Re: Draft on constraint-based routing Yao-Min Chen
- Re: Draft on constraint-based routing Guo, Liang
- Re: Draft on constraint-based routing Bala Rajagopalan