
Understanding ATM DXI Concepts
117375-A Rev. A 2-17
AAL 5
In AAL 5, only a trailer attaches to the data from the higher layer protocols to
create a CS PDU. AAL 5 divides the PDU into a 48-octet SAR PDU; however, it
does not add an SAR header and trailer. This 48-octet SAR PDU becomes the
payload of the ATM cell (Figure 2-11).
Figure 2-11. ATM Adaptation Layer 5
Note: AAL 5 does not attach an SAR header or trailer to the PDU.
Service data unit (SDU)
SAR PDU
ATM cell
SDU
SAR PDU
SAR PDU
ATM cell
ATM cell
AAL 5
Convergence
sublayer
AAL 5
SAR
layer
ATM
layer
AAL
layer
Service
class
Trailer
ATM0005A
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