ATM Cell Formats
•User Network Interface
(UNI)
–Generic Flow Control:
Not currently in use
–VPI/VCI: Identify the
next destination of the cell (which switch)
–Payload Type:
Data/control, congestion, terminating
–Congestion Loss
Priority: High/low, determines QoS
–Header Error Control:
Weak CRC on header only
•Network-to-Network
Interface (NNI)
Figure 20.9:
UNI Cell Header
UNI Cell Header
Figure 20.10:
NNI Cell Header
NNI Cell Header
