The MPLS WG Archive

[Curtis Villamizar <curtis@avici.com>]

In message <20000427120633.D2129@doit.wisc.edu>, "James R. Leu" writes:
> On Thu, Apr 27, 2000 at 11:28:05AM -0400, Curtis Villamizar wrote:
> > 
> > In message <20000427101728.C2129@doit.wisc.edu>, "James R. Leu" writes:
> > > 
> > > I had a design built around an ATM network that did just this.  A real
> > > plus to this idea is if the tunnels to the others EBGP speakers were
> > > created dynamically as soon at they were learned. (ie each time a new
> > > BGP next hop is learned a tunnel is created to that BGP next hop)
> > > 
> > > Is this a new idea or is this the same idea as BGP short cuts?
> > 
> > 
> > James,
> > 
> > In implementations that I am aware of, the tunnel goes to the peer and
> > is intended to be configured according to a historic bandwidth
> > statistic, typically 95 percentile originally suggested by Awduche.
> > There seems to be some interest in using CR with the greater of a
> > configured value and a measured value (filtered, of course), but I
> > have not seem strong interest in using a measured value only and
> > automatically setting up LSPs to either IBGP peers or as new IBGP next
> > hops are learned (though I personally like the idea a lot, but more
> > likely using IBGP peers rather than learned next hops).
> 
> The reason for using the BGP next hop is to solve the case when you use a
> route reflector.  In which case each IBGP speaker only has one peer, but
> many BGP next hops.

To further clarify current practice as described by ISPs using
MPLS-TE, the LSP generally terminates at the router ID and the next
hop is associated with the LSP for the router ID of the LSR adjacent
in the IGP to the next hop (and closest in TE terms, which is again
advertised by the IGP).  The next hop is preserved across route
reflectors and confederations and the IGP is also unaffected.

Curtis