[nsp] Calculating ATM Cell transfer rates

Alex Foster afoster at gammatelecom.com
Wed Feb 25 11:26:28 EST 2004

I am trying to pin down the correct way of calculating ATM cell rates
from a given speed in bps.  I have read various documents that contradict
each other - my understanding of the correct method is as follows:

For UBR/VBR traffic only

Line rate of 10Mbps
ATM cell rate = 10000000 / 8 / 48 = 26041 cps

Given that only 48 bytes are used for payload.

For CBR traffic only

Line rate of 2.048Mbps
ATM cell rate = 2048000 / 8 / 47 = 5447 cps

Given that only 47 bytes are used for payload (1 byte used for AAL1 Header)

I have seen some references that claim you use the full 53 bytes when
the cell rate - can this be correct??  If anybody has the definitive answer
I would
love to know.


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