ATM Adaptation Layer 3/4
(AAL3/4)
•Variable Frame length
•Error control
•Variable delay
Figure 20.14
Information < 65K Bytes
Information < 65K Bytes
Pad
BEtag
AL
Type
BEtag
BA
CS Header
Length
 CS Trailer
CS-PDU
Bytes        1               1              2             0-3          1              1                 1
SAR Header
CS Header
40 bytes Payload
SAR Trailer
2 4 40     2   bytes                  2                   44                       2
SAR Header
44 bytes Payload
SAR Trailer
SAR-PDU
ST
SN
MID
LI
FCS
2          4           10    bits        6            10   bits