NAME

ec − 3Com 10 Mb/s Ethernet interface

DESCRIPTION

The ec interface provides access to a 10 Mb/s Ethernet network through a 3COM controller.  The host’s address is discovered at boot time by reading it from the device’s command register. 

The hardware consumes 8 kilobytes of Multibus memory space.  This memory is used for internal buffering by the board.  The board starts at standard addresses 0xE0000 or 0xE2000.  The board must be configured for interrupt level 3. 

The interface software implements an exponential backoff algorithm when notified of a collision on the cable. 

The interface handles the Internet protocol family, with the interface address maintained in Internet format.  The three low-order bytes of the board’s built-in Ethernet address are used as the 24-bit Internet address, and the network number is taken from the flags as described above.  The software assumes that all Ethernet addresses on the network will have the same three high-order bytes. 

DIAGNOSTICS

ec%d: send error.  After 16 retransmissions using the exponential backoff algorithm described above, the packet was dropped. 

ec%d: input error (offset=%d).  The hardware indicated an error in reading a packet off the cable or an illegally sized packet.  The buffer offset value is printed for debugging purposes. 

ec%d: can’t handle af%d.  The interface was handed a message with addresses formatted in an unsuitable address family; the packet was dropped. 

SEE ALSO

net(4), inet(4f)

BUGS

The PUP protocol family should be added. 

The interface hardware is not capable of talking to itself.  The software implements local sending and broadcast by sending such packets to the loop interface.  This is a kludge. 

Backoff delays are done in a software busy loop.  This could degrade the system if the network experiences frequent collisions. 

A better mapping from Ethernet to Internet addresses is needed if one is to mix controllers from different vendors on a network. 

Sun System Release 0.3  —  2 May 1983