Speakeasy has published a white paper on our network architecture, located here:
The information you're asking for is specifically documented on page 15 of the white paper.
Basically, the last mile connectivity (supplied by Covad, New Edge Networks, Qwest, AT&T, etc. depending on your location and subscribed service) from your location to the Central Office is connected directly to a DSLAM (DSL Access Multiplexer). For lineshare ADSL, additional components such as voice/data splitter cards exist at the CO as well.
Once the traffic is terminated at the DSLAM, it's aggregated to an ATM circuit (DS3, OC3, etc.) by our vendor to their BPX within their ATM network.
The handoff from our vendor to Speakeasy occurs on a DS3 or OC3 referred to as a backhaul. Most of our Points of Presences (POPs) have multiple backhauls, often a combination of DS3's and OC3's to haul our customer's traffic to our POP.
Once you're at the POP, our edge router handles the subscriber piece of the equation, hands the traffic off to our core router, which routes your traffic through our private network, to a peering partner or out to the Internet.
The white paper does a much better job of elaborating on the details, but this should give you a start.
More information on our network is available at:
Email - email@example.com
www.speakeasy.net Broadband for Open Minds