You may be out of luck. OCS doesn't support any sort of downstream distribution, so your A/V conferencing server will be sending at least N audio streams and N video streams during a conference, where N is the number of conference participants. Even if you had no other traffic on your 2mb line you could only accommodate 5.8 concurrent A/V streams to that location at full fidelity. The RTAudio and RTVideo codecs will scale down, but based on what you're experiencing there is likely still too much data on the wire for a good experience.