The idn driver is a style-2 Data Link Service provider. All M_PROTO and M_PCPROTO-type messages are interpreted as DLPI primitives. For the idn driver to associate the opened stream with a particular device (ppa), you must send an explicit DL_ATTACH_REQ message. The ppa ID is interpreted as an unsigned long and indicates the corresponding device instance (unit) number. The DL_ERROR_ACK error is returned by the driver if the ppa field value does not correspond to a valid device-instance number for the system. The device is initialized on first attach and de-initialized (stopped) on the last detach.

• The maximum SDU is configurable by using the idn.conf file and has a range of 512 bytes to 512 Kbytes. The default value is 16384 bytes.
• The minimum SDU is 0.
• The Service Access Pointer (SAP) address length is 8.
• The MAC type is DL_ETHER.
• The SAP length value is -2, meaning the physical address component is followed immediately by a 2-byte SAP component within the DLSAP address.
• The service mode is DL_CLDLS.
• Optional quality of service (QOS) is not presently supported; accordingly, the QOS fields are 0.
• The provider style is DL_STYLE2.
• The version is DL_VERSION_2.
• The broadcast address value is Ethernet/IEEE broadcast address (0xFFFFFF). The idn driver supports broadcast by issuing messages to each target individually. The idn driver is inherently a point-to-point network between domains. When the idn driver is in the DL_ATTACHED state, the user must send a DL_BIND_REQ request to associate a particular SAP with the stream. The idn driver interprets the SAP field within the DL_BIND_REQ message as an Ethernet type and valid values for the SAP field are in the range of 0 to 0xFFFF. Only one Ethernet type can be bound to the stream at any time.

If a SAP with a value of 0 is selected, the receiver will be in 802.3 mode. All frames received from the media having a type field in the range of 0 to 1500 are assumed to be 802.3 frames and are routed up all open streams which are bound to SAP value 0. If more than one stream is in 802.3 mode, then the frame will be duplicated and routed up as multiple stream DL_UNITDATA_IND messages.

In transmission, the driver checks the SAP field of the DL_BIND_REQ to determine if the SAP value is 0, and if the destination type field is in the range of 0 to 1500. If either is true, the driver computes the length of the message, (excluding the initial message block M_PROTO mblk) of all subsequent DL_UNITDATA_REQ messages and transmits 802.3 frames that have this value in the MAC frame header length field.

The driver also supports raw M_DATA mode. When the user sends a DLIOCRAW ioctl, the particular stream is put in raw mode. A complete frame and a proper ether header is expected as part of the data.

The DLSAP address format consists of the 6-byte, physical address component (Ethernet) followed immediately by the 2-byte SAP component (type), producing an 8-byte DLSAP address. Applications should not hardcode to this particular implementation-specific DLSAP address format, but instead should use information returned in the DL_INFO_ACK primitive to compose and decompose DLSAP addresses. The SAP length, full DLSAP length, and SAP physical ordering are included within the DL_INFO_ACK primitive. The physical address length can be computed by subtracting the SAP length from the full DLSAP address length or by issuing the DL_PHYS_ADDR_REQ message to obtain the current physical address associated with the stream.

When the idn driver is in the DL_BOUND state, you can transmit frames on the IDN by sending DL_UNITDATA_REQ messages to the driver. The driver then routes received IDN frames up the open and bound streams having a SAP which matches the Ethernet type as DL_UNITDATA_IND messages. If necessary, received IDN frames are duplicated and routed up multiple open streams. The DLSAP address contained within the DL_UNITDATA_REQ and DL_UNITDATA_IND messages consists of both the SAP (type) and physical (Ethernet) components.

In addition to the mandatory connectionless DLPI message set, the idn driver supports the following primitives:

The DL_ENABMULTI_REQ and DL_DISABMULTI_REQ primitives which enable or disable, respectively, the reception of individual multicast group addresses. A set of multicast addresses may be iteratively created and modified on a per-stream basis using these primitives. These primitives are accepted by the driver in any state following the DL_ATTACHED state.

The DL_PROMISCON_REQ and DL_PROMISCOFF_REQ primitives, which with the DL_PROMISC_PHYS flag set in the dl_level field, enable or disable, respectively, the reception of all promiscuous frames on the media, including frames generated by the local domain. When used with the DL_PROMISC_SAP flag set in the dl_level field, these primitives enable or disable, respectively, the reception of all SAP (Ethernet type) values. When used with the DL_PROMISC_MULTI flag set in the dl_level field, these primitives enable or disable, respectively, the reception of all multicast group addresses. The effect of each is always on a per-stream basis and independent of the other SAP and physical level configurations on this stream or other streams.

The DL_PHYS_ADDR_REQ primitive which returns the 6-octet, Ethernet address associated with (or attached to) the stream in the DL_PHYS_ADDR_ACK primitive. This primitive is valid only in states following a successful DL_ATTACH_REQ request.

Because the driver maintains domain address information in the address to direct packets to the correct destination, the DL_SET_PHYS_ADDR_REQ primitive is not allowed.