The reality is that is an SDH/SONET backbone underlying most of these Ethernet networks.

That may be so (however, numbers for the national provider I work for do not tend to bear this out). But does it matter? People presumably use Ethernet because it is inexpensive, easily available, well known, etc. Yes, if the underlying technology is SDH *or* DWDM with an SDH type interface, I know *I* would prefer to use the SDH interface - because it gives me the SDH OAM we all know and love. But if my router vendor charges me a 10-30% premium for using cards with an SDH interface, then Ethernet is going to win every time... There are vendors that supply cards where the optics can be reconfigured for 10Gig Ethernet LAN *or* WAN (SDH) interface, and where you don't have to pay a premium. The Juniper MX series is an example. But real SDH cards with the corresponding lower encapsulation overhead still come at (high) price. Steinar Haug, Nethelp consulting, sthaug@nethelp.no