The MPLS WG Archive

[Grenville Armitage <gja@lucent.com>]

Krishna Bala wrote:
> 
> Jagan,
> Just to beat a dead horse .. the difference between the open model
> and the overlay is just that the overlay model typically suggests that
> there would be N^2 connectivity (i.e., every router, for instance, is
> statically connected to every other). In any case, the open model allows
> for fully dynamic operation. The overlay model suggests static operation of
> the optical layer.

This isn't the definition of "overlay model" that has been used in
the IETF for awhile. Static linking of all routers" is simply one
instantiation. The key differentiator of an overlay model is the
topological independence of the underlying and overlaying 'layers'.
E.g. in an earlier century we talked about IP/ATM overlay models where
the IP topology was logical wrt the switch-link topology of the
underlying ATM network. The connectivity itself was static, soft,
or dynamic as needed - however, the model was 'overlay' in each case.

cheers,
gja
________________________________________________________________________
Grenville Armitage                    http://members.home.net/garmitage/
Bell Labs Research Silicon Valley