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Framing and DL_INFO_REQ

To support the TCP/IP stack available with Open Transport, CSMA/CD drivers must support both Ethernet and 802.2 framing (including full SAP/SNAP binding). Because the DLPI specification does not let a driver support multiple kinds of framing, it is ambiguous in specifying how to fill out the dl_mac_type field of a dl_info_ack_t. Open Transport has specified that the default value of this field should beDL_ETHER. Clients may send an M_IOCTL message with the ioc_cmd field set to kOTSetFramingType and its chained data block containing a UInt32 value with a single bit set. If this value is the constant kOTFraming8022, then subsequent DL_INFO_REQ requests should set the dl_mac_type field to DL_CSMACD. If the value is not that constant, then subsequent DL_INFO_REQ requests should set the dl_mac_type field to DL_ETHER.

IMPORTANT

The only thing the foregoing M_IOCTL message affects is the contents of the DL_INFO_ACK. The framing that is actually used by the driver is specified in the bind.