The only example of a technology that comes to mind straight away that truly died out is/was SMDS, though I'm sure there are are a few others.
From what I remember, only a handful of telcos offered SMDS back in its
heyday (mid-90s), and most, if not all of those no longer offer it. I recall seeing some tariff filings from Verizon some time ago where they were planning to shut the service off because the customers that used it had been migrated to other technologies and some of their vendors had already dropped support for it. My workplace migrated the last customer off SMDS maybe about 2 or 3 years ago, but most of them were moved several years before that. My understanding is Vz could no longer buy gear to support SMDS and
On Wed, Nov 3, 2010 at 5:42 PM, Justin M. Streiner <streiner@cluebyfour.org> wrote: pretty much had to cannibalize existing equipment to keep it running. At one point when we still had 40-some customers on one SMDS DS3 hub circuit, we had an outage that spanned 3 days (fortunately into a weekend). Vz seemed to have only a few techs who were clueful on smds and, unless we were working with one of them, very often our techs would have to instruct Vz what to do (typically reloading all the addresses would restore service, IIRC).