Hi I'm trying to ensure optimal bandwidth usage for our VoIP solution. The last mile link to the customer is ATM. I have done some calculations, and unless I'm missing something here it seems 1 voice packet will always be split across two ATM cells. I'm not finding a good doc that can break this down into detail. Voice usage per packet: Codec: G729a, using 20ms sample size, 20 byte payload = 20 bytes. Layer3: IP/RTP/UDP header = 40 bytes Bandwidth required = at least 60 byte packet. ATM Cell: 53 bytes - 5 overhead - 8 AAL trailer Bandwidth available = at most 40 bytes. My first question is: How does the Cisco voice bandwidth calculator fit G729 on 10ms or 20ms or 30ms payload into 1 Cell? Do they assume cRTP is enabled? Then, I'm not finding a good doc on how to effectively calculate bandwidth usage for cRTP across ATM. Configuring it via a virtual-template interface seems straight forward though. Lastly, if I manage to get a G729 packet squeezed into 1 cell, apart from the obvious save in bandwidth consumption, should there be any other improvement in the solution as a whole? Regards, kris "Morality is moral only when it is voluntary." Lincoln Steffens Please note: This email and its content are subject to the disclaimer as displayed at the following link http://www.is.co.za/legal/E-mail+Confidentiality+Notice+and+Disclaimer.htm. Should you not have Web access, send a mail to disclaimers at is.co.za and a copy will be emailed to you.