MAC addresses

A MAC address is an identifier of a node or group of nodes on the network that determines the location from which data is received and to which data is sent. The three types of MDI destination addresses are:

Unicast

data is sent to a specified address

Multicast (MCA)

data is sent to a group address. Use the mdi_valid_mca(D3mdi) function to validate a multicast address.

Broadcast

data is sent to all machines.

MAC addresses are accessed and controlled with the following:

MDI ioctls

MACIOC_SETMCA, MACIOC_SETALLMCA, MACIOC_DELMCA, MACIOC_DELALLMCA, MACIOC_GETADDR, MACIOC_PROMISC, MACIOC_GETRADDR, MACIOC_SETADDR, as documented on the Intro(DSP) (on $osr6;) or Intro(4dsp) (on UnixWare 7.1.4) manual page.

The size of a MAC address is media dependent, and is implied by the media type that the driver returns in the MAC_INFO_ACK(D7mdi) primitive. For Ethernet, CSMA/CD, Gigabit Ethernet, Token Ring, and FDDI media, the MAC address is 6 octets. The MDI kernel functions that utilize these addresses assume the 6 octet size.

Link layers such as ISDN that do not utilize MAC addresses should respond to the MACIOC_GETRADDR primitive so that upper-layer calls will fail gracefully. Any ioctls that are not supported must be NAK'ed by the driver.