ec(4) Unsupported ec(4)Nameec - 3Com 10 Mb/s Ethernet interface
device ec0 at uba0 csr 0161000 vector ecrint eccollide ecxint
The interface provides access to a 10 Mb/s Ethernet network through a
The hardware has 32 kilobytes of dual-ported memory on the UNIBUS.
This memory is used for internal buffering by the board, and the inter‐
face code reads the buffer contents directly through the UNIBUS.
The host's Internet address is specified at boot time with an SIOCSI‐
FADDR ioctl. The interface employs the address resolution protocol
described in to dynamically map between Internet and Ethernet addresses
on the local network.
The interface software implements an exponential backoff algorithm when
notified of a collision on the cable. This algorithm utilizes a 16-bit
mask and the VAX-11's interval timer in calculating a series of random
backoff values. The algorithm is as follows:
1. Initialize the mask to be all 1's.
2. If the mask is zero, 16 retries have been made and we give up.
3. Shift the mask left one bit and formulate a backoff by masking the
interval timer with the mask (this is actually the two's comple‐
ment of the value).
4. Use the value calculated in step 3 to delay before retransmitting
the packet. The delay is done in a software busy loop.
The interface normally tries to use a ``trailer'' encapsulation to min‐
imize copying data on input and output. This may be disabled, on a
per-interface basis, by setting the IFF_NOTRAILERS flag with an SIOC‐
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 debug‐
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 Alsointro(4n), inet(4f), arp(4p)