DLC FDDI Direct Network Services

Some users wish to handle their own unnumbered information packets on the network without the aid of the data link layer within the fiber distributed data interface (FDDI). A direct network interface allows an entire packet to be generated and sent by users once their service access point (SAP) has been opened. This allows full control of every field in the data link header for each write issued. Also provided is the ability to view the entire packet contents on received frames. The criteria for a direct network write are:

• The local SAP must be valid and opened
• The data link control byte must indicate unnumbered information (0x03).