If your telco's LTU doesn't terminate in Ethernet, the first avenue of investigation has to be getting a better telco. Failing that (or if running your own dark fibre or whatever), then yes, you do need a T1 or X.21 or whatever to Ethernet bridge, possibly even from Cisco, but that constitutes evidence of collusion between your telco and the "enterprise" networking vendors, not of any technical need. The first company I worked at that had an Internet connection, found that we had to spend £1500 on a Cisco "router" because the British Telecom LTU didn't terminate in RS232 or Ethernet or anything sane like that which we could just run into the Linux firewall, but in X.21. And that for a just 64kbps leased-line!