DF_CTL is a one-byte field that specifies the presence of an optional header
Optional Headers
O F
O F
S
Header Network Header
Header
Assoc. Header
Device Header
Payload
Payload
CRCCRC
O F
O F
E
The DF_CTL field is a one-byte field that specifies the presence of an optional header:
• The network header can be used for routing between Fibre Channel networks of different fabric address spaces, or between Fibre Channel and other networks. If a network header is present, the network header is the first 16 bytes of the data field and is only present in the first data frame of the first sequence.
• The association header is provided to support system architectures that require more than two levels of identifiers, and is only present in the first data frame of the first sequence. For example, Fibre Channel defines sequence IDs and exchange IDs; a system might need to define a transaction ID, and would use the association header for this purpose.