At our house we have Optimum Voice, which is Cablevision’s VOIP service. It works perfectly well with good call quality and a decent web admin panel. It even let’s you forward a .wav file of your voicemails to PhoneTag for transcription which is truly useful since Susan and I see both out of the house all day. But it’s not really VOIP as it was meant to be. The service is delivered in blackbox fashion in the form of a cable modem with two phone jacks on the back (we have two lines at home). I asked about SIP phones and the answer was simply ‘no we don’t support them.’ Now I am pretty sure that Cablevision did not build something crazy and proprietary (although one never knows). So inside the cable modem there is probably a clean interface between SIP and the part that’s driving the analog jacks but no obvious access to that. By looking on the Internet I found various folks on other cable systems who had figured out how to hack into the modem box to identify the SIP settings. I don’t have the time to try that for Optimum and the particular modem we have, but I have found a great alternative. CallCentric has a wonderful self service VOIP offering that was not only extremely easy to set up but offers great quality and competitive rates. Now I have a SNOM 300 phone which I can plug anywhere into our home network (or any other IP network for that matter) and get the full on VOIP experience as it was meant to be. So far I highly recommend this to anyone with a home office or small business / startup (will provide updates if I encounter any glitches).