clocking, only the implications of clocking, conspicuous by it's absence. After thoroughly understanding this picture, how do we relate pay- load to a network transport facility? The classic Internet Netizen approach is simply to "give me all you've got." If that were possible, the content might get there before its time came for presentation, and wouldn't that be a can of worms? More to the point, IP-layer 3 trans- port depends on lower layer 2 for clocking. This says there are band- width constraints and structure, SO like carrying ATM over PDH or SONET/SDH we can simply take the same E3/T3/J3 channel interface and determine maximum potential payload under the con- straints imposed by IP, UDP, and RTP protocols. Now it becomes a simple arithmetic exercise, not unlike that used in TDM and ATM. First, the maximum potential payload that can be expected to be available from a DS3 channel interface is 44,209,694 bits. This means only SO many packets can pass. Since the rate must be constant and each frame consists of 6,336 bits, dividing the available channel rate by 6,336 results in a fractional number (6,977.5). So drop the fraction and subtract 4 making it 6,977 frames, which is an octal number. Now multiply 6,977 times 6,336 bits per frame, and the resulting maximum IP payload is 41,973,632bps. APPENDIX TABLE 2 Payload Capacity in TDM, ATM and IP PDH Transmission Octal Y/N Bytes Circuits DS3 Channel Rate 44,736,000 5,592,000 DS3 Framing Overhead 526,306 65,788.3 DS3 Payload Capacity 44,209,694 5,526,211.8 Transmission Unit Payload 64,000 8,000.0 DS3 Facility Payload 43,008,000 5,376,000.0 672.0 Required 1,201,694.0 150,211.8 Total (Payload+OH+Stuffing) 44,736,000 5,592,000.0 Bytes Cells ATM Cell Payload ATM Overhead ("Cell Tax") Transmission Unit Payload ATM Cells On DS3 Payload 44,209,694 13,033.5 104,268.1 Next Lowest Octal Number Evenly 44,209,632 5,526,204.0 Divisible by 424 Additional Stuffing Required Overhead 526,368 65,796.0 Maximum Practical ATM Payload in DS3 44,209,632 5,526,204.0 104,268.0 Total (Pay