Ok, thanks for all the responses so far! To summarize what I've gathered from the answers and reading through the pointed out websites. For ordering T1 leased-line services I want the following: o Router port with integrated CSU/DSU (instead of going T1->X.21->Router) [this was clear to me from the beginning] o Linecode B8ZS (because this gives clear channels with 64k rate) o Framing ESF (because this supports line diagnostics) o SmartJack with demarcation point in the office (or same floor) instead of the building entrance point o For lines that come with a SmartJack (aka HDSL2) I only need 'short-haul' T1 line (<655 feet, called DSX-1) If I am unlucky the T1 gets delivered either directly or via repeaters as four-wire service from the central office which makes it 'long-haul' T1 with line segment lenth of up to 6,000 feet between repeaters (called DS-1). The remaining question I have is how common are the two types of DSX-1 (short-haul with SmartJack) vs. DS-1 (long-haul directly to CO) lines? Anyone with experience how this is being handled by the various Telcos? Maybe percentages one type versus the other? Are there major Telcos which clearly do not support the above settings? To know who to avoid when procuring services. -- Andre