Historically we had a lot of leased lines and technologies like SMDS with ISDN being the backup medium or small-site link. ATM was heralded as the way of the future but again it never really gripped the masses. Currently, everyone seems to be moving to MPLS which is packaged under different names by providers but is basically MPLS underneath. And while there's still a lot of ISDN in use, ADSL and SDSL is becoming very popular as both a backup solution and as a very cost-effective small-site link
