[Isis-wg] RE: FYI Draft Metrics and Resource Classes for TE

[Don Fedyk]

Dan and Angela:

Yes, As you both pointed out it maximizes the bandwidth only on a next hop
link basis not a path basis. I will correct the text.
This is not key to the arguments of the draft but it does illustrate
how bandwidth allocation is advantageous. 

Thanks,
Don

> -----Original Message-----
> From: Chiu, Angela L, ALSVC [mailto:alchiu@att.com]
> Sent: Thursday, October 21, 1999 4:53 PM
> To: awduche@UU.NET; Fedyk, Don [BL3:2001-I:EXCH]
> Cc: te-wg@UU.NET; isis-wg@external.juniper.net
> Subject: RE: FYI Draft Metrics and Resource Classes for TE
> 
> 
> Jon,
> 
> I echo what Dan pointed out earlier. By making link cost to 
> be the inverse
> proportional to available bandwidth, it only says that the 
> least cost link
> is the one with the most available bandwidth.
> 
> 	Your statement that 
> 	"the shortest path corresponds to the path with the 
> most bandwidth"
> is not even true for paths with the same number of hops. For 
> example, let
> link cost to be the inverse of the available bandwidth. 
> Available link bandwidth on path A: 1, 6, 6, 6, 6, 6, 6 => 
> path available
> bandwidth = 1, with path cost = 2
> Available link bandwidth on path B: 2, 3, 3, 3, 3, 3, 3 => 
> path available
> bandwidth = 2, with path cost = 2.5
> 
> Hope the example helps.
> 
> Angela Chiu
> 
> AT&T Labs
> Room C4-3A22
> 200 Laurel Ave.
> Middletown, NJ 07748
> Tel. (732) 420-2290
> Fax (732) 368-1746
> Email: alchiu@att.com
> 
> > -----Original Message-----
> > From:	awduche@UU.NET [SMTP:awduche@UU.NET]
> > Sent:	Thursday, October 21, 1999 4:26 PM
> > To:	dwfedyk@nortelnetworks.com
> > Cc:	te-wg@UU.NET; isis-wg@external.juniper.net; awduche@UU.NET
> > Subject:	Re: FYI Draft Metrics and Resource Classes for TE
> > 
> > Jon,
> > 
> > A note on your draft...
> > 
> > You made the following assertion in the draft..
> > 
> >  "On the other hand, it is also possible to look at bandwidth as an
> >   additive metric by using link costs that are in inverse proportion
> >   to available bandwidth; in such cases, the shortest path
> >   corresponds to the path with the most bandwidth."
> > 
> > This assertion is, of-course, false (that is that the shortest
> > path based on inverse bandwidths is the one with the most 
> > bandwidth). You may wish to correct it in the next iteration 
> > of your draft. 
> > 
> > Regards,
> > /Dan
> > 
> > 
> > Don Fedyk said:
> > > 
> > > We have submitted the draft: draft-fedyk-mpls-te-metrics-00.txt
> > > for review to the following working groups:
> > > - Traffic engineering
> > > - MPLS
> > > - IS-IS
> > > - OSPF
> > > 
> > > We asked to present it to the TE and ISIS working groups.
> > > 
> > > Abstract
> > > 
> > >    There has recently been a lot of activity in defining 
> the components
> > >    for MPLS-based traffic engineering.  This includes the recent
> > >    extensions of the Interior Gateway Protocols (IGPs) to 
> carry metrics
> > >    and resource class information about links.  This memo explores
> > >    additional metrics that are useful for traffic 
> engineering.  We also
> > >    describe some of the subtleties associated with the use of the
> > >    resource class (or color) vector that has been defined 
> in the IGP
> > >    extensions.
> > > 
> > > For those interested, a copy is avialable at:
> > > http://www.ee.duke.edu/~ag/final-papers/mpls-te-metrics.txt
> > > Thanks,
> > > -Don Fedyk and Anoop Ghanwani
> > > 
>