AAL5 Frame Fields
Pad: used to fill-out frame to be an even multiple of 48 bytes. Allows for frame meta-data to always appear at end of entire AAL5 frame
UU: user-to-user info, treated as opaque data by ATM, unspecified [in 1996]
CPI: a type field, current value of zero
Length: length of overall PDU
CRC: CRC over entire payload