Coming from an academic research background, I need a reality check. I would appreciate your answers/thoughts etc. to the questions I have below on WANs. 1- are there any all-IP backbones? what is the layer 2 in IP backbones (PPP, ATM, Frame relay...)? 2- how commonly is IP over ATM used? Do network operators really care about the cell-tax? 3- what is the approximate number of connections to a router (i.e., fan-in, fan-out of a router (i) at the edge, (ii) at the core, and (iii) at the backbone? 4- what is the maximum distance between any two points in a autonm. system? 5- what is the approximate ratio of copper/fiber at the edge, core, backbone links? 6- how tight is the physical space in the router rooms (i.e., is it almost a must to take out an old box in order to add one)? 7- in case of a node/link failure what is the average/approx period of time for (i) detection and (ii) recovery I thank you in advance Bulent _____________________________________________________ Bulent Yener Information Sciences Research Center Bell Laboratories, Lucent Technologies 600 Mountain Avenue, Room 2T-314 Murray Hill, NJ 07974 email: yener@research.bell-labs.com phone: (908) 582 7087 fax: (908) 582 1239 _____________________________________________________