A 3 bit field in the ATM cell header that indicates whether a cell contains user information or Connection Associated Layer Management information in its payload and also whether a cell experienced congestion. Its currently defined values are:
000 User data cell, congestion not experienced, SDU-type = 0 001 User data cell, congestion not experienced, SDU-type = 1 010 User data cell, congestion experienced, SDU-type = 0 011 User data cell, congestion experienced, SDU-type = 1 100 Segment OAM F5 flow related cell 110 Reserved for future traffic control and resource management 111 Reserved for future functions
See also - ATM UNI Cell Structure
- Payload Type Identifier