Broadband Modem (Hardware) → back to back modem configuration

I'm looking to set up a direct link between two computers using back to back adsl modems. Googling seemed to leave me more confused than when I started so I thought I'd come here and get some questions answered and misconceptions corrected

1) What is technical difference between CPE and CO modems? I understand that you need at least one modem capable of operating in CO mode for a back to back configuration to work but I am not sure why. Any whitepapers on CPE modem to DSLAM connections would probably help greatly.

2) Is there any where I can find a list of consumer grade modems that can operate in CO mode? (provided, that is, that implementing CO mode in a CPE modem is non-trivial)

3) Can back to back configurations work over the regular telephone network? It seems it would just be a matter of ringing the other person up, letting them answer, then allowing the modems to do their thing, no?

Thanks in advance.

Only some specific SDSL Router/Modems can perform "Back 2 Back" connections. It will usually require a dedicated run of copper no longer than 18,000 cable feet. It will likely not work by calling another person and trying to get the modems to connect over the phone call connection.

Some Back to Back capable SDSL Routers
• Netopia R7100-C SDSL Router
• Siemens/Efficient Speedstream 5851 SDSL Router
• 3Com OfficeConnect 840 SDSL Router

[I see these are all SDSL modems. Does this mean that adsl does not work for back to back, or just that there are no back to back capable adsl modems that you know of?

Also, how much does your typical dedicated (without built in router) modem "do" besides simply modulating and demodulating the digital signal? Are they performing any handshaking, sanity- or error-checking besides that required for PPPoE (which is handled by the router)? Could I, for instance, send say, raw ethernet packets or even nonsense bits through one if I wanted to?

Thanks again, and for the prompt reply.

Only SDSL as I posted and only some of them as not all SDSL Routers will even work. Sometimes it even requires a specific Firmware revision or specific Model Number or it will not work. ADSL will not work back to back as a DSLAM is required.

»DSL-300G back-2-back

Back-to-Back Connections and ADSL
»tcpmag.com/qanda/article ··· lsID=417