"Chris A. Icide" <chris@nap.net> writes:
We use ATM for two reasons, 1) it's still significantly cheaper than long-haul circuits of the same capacity,
My canonical explanation for this is that people are actually deluding themselves into thinking that ABR will work and the "quiet moments" across a large number of VCs can effectively be statmuxed out of existence without hurting goodput. The apocryphal reason is that people with too much influence in carriers' decision making processes are desperately trying to gain enough revenue to justify the ridiculously large amount of money spent on deploying ATM and convincing everyone it was the way the truth and the light of the future, even if that revenue isn't as profitable as selling raw bandwidth. (cf. the canonical explanation) There are cases, however, involving inter-carrier handoffs where muxing at the virtual tributary/virtual container level doesn't work particularly well end-to-end, thus making ATM an alternative to SDH<>PDH<>SDH conversions. These cases are becoming rarer over time as people deploy modern SONET/SDH muxing and terminal equipment.
2) it provides some interesting abilites that are only now beginning to show up in the mainstream IP hardware.
Ok, I'll bite: which ones? The only ones I can think of right off the top of my head involve the counting problem. (Modulo easy deployment of cisco's rate limiting and/or the ability to make tunnels fast). Rather, I guess the question is, which of the "interesting abilities" (which I agree are interesting in a theoretical sense) are actually practically useful when running part of the Internet? Sean.