• Construction and transport use exactly the same methodology as data frames.
• Not seen by the user • Used to perform Fibre Channel functions between ports at the FC- 2 layer using FC-CT (Fibre Channel Common Transport)
• Sometimes allowed to ‘break the rules’ for normal data frames for operational reasons
• May ‘extend’ the information beyond what can be communicated in the header of the frame. Has to use the payload of the frame for extended information.